Synergistic Inhibition of Mild Steel Corrosion in Seawater...
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Research Article Synergistic Inhibition of Mild Steel Corrosion in Seawater and Acidic Medium by Cathodic Protection and Monodora myristica Using Zinc Anode Imoh Ukpong, 1 Omolara Bamgboye, 1 and Oladega Soriyan 2 1 Department of Industrial Chemistry, Covenant University, Ota, Ogun State, Nigeria 2 Department of Chemistry, Obafemi Awolowo University, Ile Ife, Osun State, Nigeria Correspondence should be addressed to Oladega Soriyan; [email protected] Received 30 August 2018; Accepted 1 November 2018; Published 27 November 2018 Academic Editor: Ramana M. Pidaparti Copyright © 2018 Imoh Ukpong et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e synergistic inhibition of mild steel corrosion in seawater and 0.1M sulphuric acid by the cathodic protection and Monodora myristica was carried out through the weight loss and the linear polarization resistance (LPR) measurement. e results showed that in seawater, the synergism was not too effective for the protection of steel, whereas in 0.1M sulphuric acid, there was a great synergism between cathodic protection and the oil extracts of Monodora myristica, having an efficiency (IE%) of 102.89% at 15 mL of the oil extracts. For the linear polarization resistance (LPR), in most of the cases, there was a slight shiſt of the corrosion potential (E corr ) and the open circuit potential (OPC) toward the positive as the volume of the oil extracts increased, thereby causing a change in the cathodic and the anodic Tafel slopes, which showed that the inhibitor is a mixed- type inhibitor. e corrosion current density (icorr) decreases as the volumes of the oil extract increase. Langmuir adsorption isotherm fitted best with an R 2 of 1 unit, indicating a good agreement with the experimental data and with Langmuir adsorption isotherm. 1. Introduction Corrosion is a phenomenon that occurs naturally in our environment. It is a process that alters a processed metal into a chemically stable form, such as its oxides, hydroxide, and sulphide [1]. All metal surfaces, excluding gold, are protected with oxide films when exposed to the atmosphere. is oxide film on the metal surface tends to disband when immersed in an aqueous solution. However, if the solution is acidic, the oxide film may dissolve completely leaving an unprotected metal surface, which is said to be in the active state [2]. In near solution, the solubility of an oxide on the surface of a metal will be reduced than in acid solution, while the degree of dissolution will tend to be smaller. e study of the soil corrosion of buried-structural materials is important because millions of miles of the buried steels or iron pipeline are used to supply the drinking water, gas, oil, and so on in the world. Many buried-structural materials, such as galvanized water supply pipelines, natural gas, and crude oil pipelines have been corroded by soils all around the world [3–9]. e study on Nigeria pipeline of crude oil (along the Obrikom- Ebocha areas) showed that the oil resistivity value decreased with increasing the moisture content and temperature [8]. e corrosion rate of the buried-structural materials is mainly influenced by six different soil parameters, namely, mois- ture content, pH, resistivity, oxidation-reduction potential, chloride, and sulfate contents [10–12]. e corrosion rate of most structures produced from mild steel (e.g., ships, tankers, reservoirs, storage tanks, and offshore platforms) used in aqueous media (e.g., seawater, oil, and soil) depends on the aqueous solution compositions and different environmental conditions such as concentration of Cl − , SO 4 2− ,S 2− ,O 2 , pH, and temperature [10–12]. Hence, corrosion protection systems must be reliable and efficient. Several compounds of inhibitors are known for these purposes [13–15]. Amongst the several methods available in preventing or controlling cor- rosion is the cathodic protection technique. is technique developed by Sir Humphrey Davy in 1824 was explained for the first time in a sequence of works offered to the Royal Society in London [16]. Cathodic protection is a method Hindawi International Journal of Corrosion Volume 2018, Article ID 5648907, 8 pages https://doi.org/10.1155/2018/5648907
Transcript of Synergistic Inhibition of Mild Steel Corrosion in Seawater...
Research ArticleSynergistic Inhibition of Mild Steel Corrosion in Seawater andAcidic Medium by Cathodic Protection and Monodora myristicaUsing Zinc Anode
Imoh Ukpong1 Omolara Bamgboye1 and Oladega Soriyan 2
1Department of Industrial Chemistry Covenant University Ota Ogun State Nigeria2Department of Chemistry Obafemi Awolowo University Ile Ife Osun State Nigeria
Correspondence should be addressed to Oladega Soriyan oladegasoriyancovenantuniversityedung
Received 30 August 2018 Accepted 1 November 2018 Published 27 November 2018
Academic Editor Ramana M Pidaparti
Copyright copy 2018 Imoh Ukpong et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
The synergistic inhibition of mild steel corrosion in seawater and 01M sulphuric acid by the cathodic protection and Monodoramyristica was carried out through the weight loss and the linear polarization resistance (LPR) measurement The results showedthat in seawater the synergism was not too effective for the protection of steel whereas in 01M sulphuric acid there was a greatsynergism between cathodic protection and the oil extracts ofMonodora myristica having an efficiency (IE) of 10289 at 15 mLof the oil extracts For the linear polarization resistance (LPR) in most of the cases there was a slight shift of the corrosion potential(Ecorr) and the open circuit potential (OPC) toward the positive as the volume of the oil extracts increased thereby causing a changein the cathodic and the anodic Tafel slopes which showed that the inhibitor is amixed- type inhibitorThe corrosion currentdensity(icorr) decreases as the volumes of the oil extract increase Langmuir adsorption isotherm fitted best with an R2 of 1 unit indicatinga good agreement with the experimental data and with Langmuir adsorption isotherm
1 Introduction
Corrosion is a phenomenon that occurs naturally in ourenvironment It is a process that alters a processed metal intoa chemically stable form such as its oxides hydroxide andsulphide [1] All metal surfaces excluding gold are protectedwith oxide films when exposed to the atmosphere This oxidefilm on the metal surface tends to disband when immersed inan aqueous solution However if the solution is acidic theoxide film may dissolve completely leaving an unprotectedmetal surface which is said to be in the active state [2] Innear solution the solubility of an oxide on the surface of ametal will be reduced than in acid solution while the degreeof dissolution will tend to be smaller The study of the soilcorrosion of buried-structural materials is important becausemillions of miles of the buried steels or iron pipeline areused to supply the drinking water gas oil and so on in theworld Many buried-structural materials such as galvanizedwater supply pipelines natural gas and crude oil pipelineshave been corroded by soils all around the world [3ndash9] The
study on Nigeria pipeline of crude oil (along the Obrikom-Ebocha areas) showed that the oil resistivity value decreasedwith increasing the moisture content and temperature [8]The corrosion rate of the buried-structuralmaterials ismainlyinfluenced by six different soil parameters namely mois-ture content pH resistivity oxidation-reduction potentialchloride and sulfate contents [10ndash12] The corrosion rate ofmost structures produced frommild steel (eg ships tankersreservoirs storage tanks and offshore platforms) used inaqueous media (eg seawater oil and soil) depends on theaqueous solution compositions and different environmentalconditions such as concentration of Clminus SO4
2minus S2minus O2pH and temperature [10ndash12] Hence corrosion protectionsystems must be reliable and efficient Several compounds ofinhibitors are known for these purposes [13ndash15] Amongst theseveral methods available in preventing or controlling cor-rosion is the cathodic protection technique This techniquedeveloped by Sir Humphrey Davy in 1824 was explained forthe first time in a sequence of works offered to the RoyalSociety in London [16] Cathodic protection is a method
HindawiInternational Journal of CorrosionVolume 2018 Article ID 5648907 8 pageshttpsdoiorg10115520185648907
2 International Journal of Corrosion
utilized to lessen the effect of rusting by decreasing thedifference in potential between the anode and cathode It isaccomplished by applying a current to the structure to besecured (such as a pipeline) from some external sourceWhenadequate current is applied the entire structure will functionas one potential hence the anode and cathode positions willcease to exist Many different types of structure utilize thiscommon technique For example it is used for pipeline locksunderground storage tanks and ship hulls protection [17]The theory behind it is to supply enough electrons to theanodic area so that it becomes cathodic thus slowing downor eliminating the anode altogether This is done throughthe use of an external anodic material that supplements thesupply of electrons to the area in danger [16] It can alsofunction by transforming undesirable anodic (active) sites ona metalrsquos surface to cathodic (passive) sites via the use of anopposing currentThis opposing current supply free electronsand forces local anodes to be polarized to the potential ofthe local cathodes [18] Cathodic protection is more reliableeffective and economical method for protection of a varietyof pipelines tanks and marine structures including shipshulls and submarines against corrosion Cathodic protectionworks primarily by depressing the natural corrosion potentialof the structure to be protected to a value where it does notcorrode [19 20] Coating alongside with cathodic protectioncan be used together Both of them complement each otherwhere possible such that one can use them in combinationto achieve the optimal economy and protection The coat-ing protects everywhere but at holidays This combinationminimizes the amount of current a cathodic protectionsystem must provide and distributes that current further andmore evenly With undercutting of the coating by corrosionmitigated a coating can last longer [21] However the coatingsystem must be compatible with cathodic protection and thelevel of cathodic protection must not be excessive Thoughnormally compatible coatings may break up due to excessivelevels of cathodic protection This gives way for corrosionto take place at the disbandment area where cathodicprotection currents may not be able to reach Several workshave been carried out by researchers on the inhibition ofmild steel using synergism of different inhibitors [22ndash24]Frunjo Ivusic et al [22] discussed the synergistic inhibitionof mild steel corrosion in seawater by cerium chloride andsodium gluconate Roya Farahmand et al [23] described thesynergistic effect of molybdenum coating and SDS surfactanton corrosion inhibition of mild steel in the presence of35 NaCl Although the synergism of cathodic protectionand plant extract inhibitors are not that common someworks have been done with them Efim Ya Layublinski [24]worked on the synergism in corrosion protection systemwith inhibitors Panpan et al [25] investigated the corrosioninhibition performance of X70 pipeline steel in seawaterusing carboxymethyl chitosan (CMCS) and Na2WO4 at acathodic protection potential of -085v (versus SCE) It wasobserved that as corrosion inhibitors CMCS and Na2WO4show a brilliant synergy for the protection of X70 pipelinesteel in seawater According to Adewole et al [26] thephytochemical antimicrobial and GC-MS of African Nutmeg(Monodora myristica) were analyzed for the phytochemical
components of Monodora myristica From this study it wasobserved that it contains some organic compounds whichhave good potential for corrosion inhibition studies Suchcompounds include alkaloid (1262) saponin (2273mgg plusmn001) tannin (0002mgg plusmn 0002) and flavonoid (0541mggplusmn 0001)
The present study is aimed at investigating the synergisticeffect of Monodora myristica (African Nutmeg) oil extractand cathodic protection on the corrosion inhibition of mildsteel in seawater and 01M sulphuric acid solution using zincsacrificial anode
2 Materials and Methods
21 Samples Collection All the samples used for this experi-ment were sourced locally The seeds of Monodora myristica(African Nutmeg) used were bought from Oja Ota market inOta Ogun State while the mild steel was brought from themild steel dealer in Ota Ogun State Seawater was collectedfrom Elegushi beach in Lekki-Ajah Lagos State
22 Preparation of 01M Sulphuric Acid 533 ml of con-centrated sulphuric acid (assay 98 and density 18) wasmeasured in a 1-liter standard flask and distilled water wasadded to make up the mark The solution was standardizedwith a standard solution of sodium carbonate (Na2CO3)
23 Preparation of Monodora myristica Extract The Mon-odoramyristica fruitswere broken so as to free the seed insideand then the seeds collected were dried in hot air oven at 80∘Ctemperature till all the water content is evaporated Afterthat the sample was weighed using a weighing balance andthe total weight of the sample was 1006456 g To improvisefilter papers (180 mm) were used to wrap the sample and tiedwith threads before inserted into the Soxhlet extractors forrefluxing The solvent used for the extraction was N-Hexaneat a temperature of 60∘C for several hours till all the extractswere collected But the solution containing the extract wasevaporated using the rotary evaporator to evaporate all thesolvent (N-Hexane) from it The oil was recovered as theextract and the volume of the oil extracted was 422273mlThe oil was stored in an amber bottle and kept in a cool dryplace
24 Metal Preparation Themild steel used for this study hasa chemical composition as shown in Tables 1 and 2
The mild steel was mechanically machined using a vicewith a hacksaw and cut into coupons (50 pieces) of dimension(3 cm times 3 cm times 02 cm) while the one used for polarizationmeasurement has dimension 01 cm times 01 cmThese couponswere all polished with series of emery papers up to 800 gritssizes starting from the coarsest to the finest grit size Thezinc sacrificial anodes were used They were also cut intoshape before use The polished coupons were degreased withethanol and allowed to dry before weighing them
25 Weight Loss Measurement The weight losses for thisstudy were carried out by measuring 400 mL of seawater and
International Journal of Corrosion 3
Table 1 Chemical components of mild steel
Elements Si Fe Cu Mn Pb Cr Ni Al P C S Co V present 0018 9936 0034 0189 0006 0025 0031 0052 0013 0142 0012 0045 0016
Table 2 Chemical composition of zinc
Elements Zn Cu Pb Fe Ti Cd Al Sn present 998 007 004 001 lt003 001 001 0003
500 mL of 01M H2SO4 acids respectively into a plastic cupand then the mild steel was subjected to the media For thecathodic protection test the galvanic (sacrificial) method ofprotection system was employed where the zinc sacrificialanodes were used and a copper wire serves as a conductorbetween the metal and the anode with a rod used as supportThese samples were weighed before and after retrieval fromthe corrodent using an analytical balance The weight losseswere all monitored at 3-day interval for the period of 21 daysof exposure After the reading the metalrsquos weight loss orgain (WL) corrosion rate (W) inhibition efficiency () andsurface coverage were calculated using the formulas givenbelow
119908119871 = 119908119894 minus 119908119891 (1)
119862119877 =143700 times 119908119871
785 times 119860 times 119879(2)
119868119864 () =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900times 100 (3)
whereWL is the difference between the initial weight and thefinal weight of the mild steel metals And Wi and Wf are thevalues for the weight loss of the steel without and with theaddition of inhibitors in the solution respectively CR is thecorrosion rate of the mild steel A is the surface area of thesteel and T is the time of immersion The value 785 is thedensity of themild steel while 143700 is the constant used forcalculating corrosion rate inMpy coupon area (cm2) W0 isthe change in weight without the inhibitor and Winh is thechange in weight with the inhibitor
However the surface coverage is a function of the degreeof coverage of the metal surface by the inhibitor moleculesMathematically it is represented as
120579 =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900(4)
where 120579 is the surface coverage
26 Electrochemical Test The linear polarization resistance(LPR) analysis test was carried out using the Autolabpotentiostat-galvanometer Nova 211 system at normal roomtemperature The Linear polarization resistance (LPR) con-sists of three-electrode system which includes the saturatedcalomel reference electrode (SCE) and the working and thecounterelectrode The SCE is the reference electrode andthe working electrode is the mild steel with an exposed
Control1 mL5 mL
10 mL15 mL
minus008minus007minus006minus005minus004minus003minus002minus001
000
Wei
ght L
oss (
g)18 208 10 12 14 164 6 222
Time (Days)
Figure 1 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in seawater
area of 1cm2 for each metal The sacrificial electrode actedas counterelectrode Prior to the measurement 100 mL ofthe corrodent (seawater01M acid) was measured into abeaker before the working electrode was dipped into seawaterand 01M sulphuric acid containing different volumes ofMonodora myristica oil extracts for 15mins until a stable opencircuit potential (OCP)was obtainedTheOCP values startedfrom -01mv and stopped at +01mv at a scan rate of 0001 mvThe values obtained for different parameters during the Tafelplots are shown in Tables 4 and 5
3 Results and Discussion
31 Weight Loss Measurement The plot for the synergis-tic effect of cathodic protection and different volumes ofMonodora myristica oil extract for steel with zinc anode inseawater is shown in Figure 1 It is observed from the plot thatthe weight loss for the cathodic protection and oil extract forsteel with zinc anode decreased with respect to time for free-inhibitor (control) 1 mL and 5mL oil extracts respectively asseen in Figure 1 but for other higher volumes of oil extracts10 mL and 15 mL the weight loss increases with time Thistrend is contrary to the expected outcome of an increase inthe weight loss of mild steel during the active period of mildsteel However the decrease in weight loss against time asshown in Figure 1 was a result of the increase in the initialweight of the mild steel The increase in the initial weightof the mild steel could be a result of possible deposits like
4 International Journal of Corrosion
Table 3 pH values for cathodic protection and different volumes of oil extract for steel with zinc in seawater
Days Control 1 mL 5 mL 10 mL 15 mL0 751 756 696 670 6523 760 695 685 672 6656 757 705 685 628 6119 775 737 708 664 62612 731 726 695 684 64015 745 720 705 692 67518 759 731 717 678 66421 740 680 665 652 645
Table 4 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in seawater environment
Extracts Vol (ml) OCP (V) Ecorr Obs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0517 -0503 0003 0003 22449E-08 31238 -1 -0587 -0604 0002 0003 91358E-08 5664 -306955 -0465 -0453 0002 0002 10141E-08 42661 54810 -0489 -0475 0002 0002 49065E-09 91520 7815 -0620 -0625 0001 0002 47488E-09 83378 788
Table 5 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in 01M sulphuric acid
Extracts Vol (ml) OCP (V) EcorrObs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0532 -0540 0004 0005 17982E-05 52847 -1 -0488 -0484 0003 0002 54309E-07 84987 96975 -0516 -0509 0003 0002 17283E-07 27228 9910 -0494 -0482 0001 0003 14303E-08 27040 999915 -0344 -0392 0005 0009 10058E-10 13271E+07 9999
CaCO3 and Mg(OH)2 on the surface of the steel that is areaction between amild steelrsquos surface and some componentsof seawater
According to Li and Du [27] calcareous deposits willform on the protected steel surface after cathodic protectionin seawater This is due to hydrogen evolution and oxygenreduction reactions
H2O +1
2O2 + 2e
minus997888rarr 2OHminus (5)
2H2O + 2eminus997888rarr 2OHminus +H2 (6)
Due to the production of OHminus the magnesium ions willreact with OHminus and are deposited as brucite of Mg(OH)2 onthe steel surface Furthermore with the change in pH nearthe steel surface the inorganic carbonic equilibrium will beupset leading to the concentration of carbonate ions and theprecipitation of CaCO3
Mg2+ + 2OHminus 997888rarr Mg (OH)2 (7)
Ca2+ + CO3 997888rarr CaCO3 (8)
As these nonconductive deposits progressively cover thesurface the flux of dissolved oxygen from seawater toward
the steel surface is limited In addition the overall rate ofthe cathodic protection reaction (4) decreases leading to areduction in the cathodic current density required and theconsumption of the sacrificial anode [28ndash32] But howeveraccording to Corrosionpedia [33] a calcareous deposit isa layer that consists of calcium carbonate and other saltsdeposited on the substratersquos surface When the surface iscathodically polarized as in cathodic protection this layeris the result of the increased pH adjacent to the protectionsurface Thus from Table 3 it showed the pH values forthe cathodic protection and different volumes of oil extractsfor steel with zinc From this table it is observed thatthe pH values decreased as the volumes of the oil extractincreased This suggests that as the pH of the electrolytedecreased there was a corresponding increase in the acidityor H+ ion concentration of the solution This is presumedto have prompted the dissolution of the calcareous depositpreviously observed on the surface of the steel Consequentlythis situation exposes the cathodic protection system to thesolution thereby activating the oxidization reaction of theanode which on the other hand caused the increase in theweight loss as observed with the 10 mL and 15 mL of the oilextract seen in Figure 1This is the reason cathodic protectionand oil extracts for steel with zinc are not very effective in theprevention of steel in a seawater environment
International Journal of Corrosion 5
2 4 6 8 10 12 14 16 18 20 22
minus10
minus08
minus06
minus04
minus02
00
Time (Days)
Wei
ght L
oss (
g)
Control1 mL5 mL
10 mL15 mL
Figure 2 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in 01M sulphuric acid
For the cathodic protection of steel with zinc in 01Msulphuric acid between the free-inhibitor (control) and the15 mL oil extracts very slight increases in the weight losswere observed though in the negative range The weightloss ranges from -10 in free-inhibitor to 000 in 15 mL oilextracts as shown in Figure 2The cathodic protection and oilextract for steel with zinc in 01M sulphuric acid suggest thecompatibility of the sacrificial anode (Zn) and the oil extractof Monodora myristica It showed that in 01M sulphuricacid the cathodic protection and oil extract of steel withzinc inhibit completely the degradation of steel It indicatedthat the synergism of cathodic protection and oil extract forsteel with zinc inhibited both the anodic and the cathodicside of the reaction forcing the weight to remain at zeroThis means that more electrons were released in addition tothe oil extract helping to protect the mild steel by stoppingcompletely both the oxidation and oxygen reduction reactionof steel
Comparing the above observations in 01M sulphuricacid and seawater it is very clear from all the plots thatthe synergistic effect of cathodic protection and oil extractof Monodora myristica for steel with zinc proves to be thebest corrosion prevention method compared to the cathodicprotection and oil extracts of steel with zinc in a seawaterenvironment
For the inhibition efficiency (IE ) for the synergisticcathodic protection and oil extract ofMonodora myristica forsteel with zinc in a seawater environment it showed that ithas the following efficiencies as shown in Figure 3 From theplots the efficiencies increase as the volumes of the oil extractincrease that is moving from the negative value which issuggested to be due to the effect of the calcareous deposit onthe surface of the steel to the positive value which is also aresult of the dissolution of the deposit However on the otherhand in 01M sulphuric acid the cathodic protection and oilextract for steel with zinc it has an inhibition efficiency of99 at 1 mL and 1028 at 15 mL as observed in Figure 4Thisis similar to the previous work by Aballe [34] who reported
1 mL5 mL
10 mL15 mL
minus140minus120minus100minus80minus60minus40minus20
020406080
100
Inhibi
tion Effi
cienc
y ()
4 6 8 10 12 14 16 18 20 222Time (Days)
Figure 3 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in seawater
2 4 6 8 10 12 14 16 18 20 22Time (Days)
990995
1000100510101015102010251030
Inhibi
tion Effi
ciency
()
1 mL5 mL
10 mL15 mL
Figure 4 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in 01M sulphuric acid
inhibition efficiency greater 100 This result suggests thatthe synergy of cathodic protection and oil extract of steel withzinc in 01M sulphuric acid showed a very strong adsorptionbond between the oil extract molecule and the surface ofthe metal which is also supported by the sacrificial zincanode Hence in 01M sulphuric acid the synergy of cathodicprotection and oil extract of steel and zinc have a very highand good inhibition efficiency when compared to that ofseawater counterpart
32 Linear Polarization Resistance (LPR) Measurement Thelinear polarization resistance plot (Tafel) for the cathodicprotection and oil extract for steel with zinc in both seawaterand 01M sulphuric acid in the absence and presence ofdifferent volumes of oil extract of Monodora myristica isshown in Figures 5 and 6 and their electrochemical parameterobtained by extrapolation of the Tafel line is shown in Tables
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
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2 International Journal of Corrosion
utilized to lessen the effect of rusting by decreasing thedifference in potential between the anode and cathode It isaccomplished by applying a current to the structure to besecured (such as a pipeline) from some external sourceWhenadequate current is applied the entire structure will functionas one potential hence the anode and cathode positions willcease to exist Many different types of structure utilize thiscommon technique For example it is used for pipeline locksunderground storage tanks and ship hulls protection [17]The theory behind it is to supply enough electrons to theanodic area so that it becomes cathodic thus slowing downor eliminating the anode altogether This is done throughthe use of an external anodic material that supplements thesupply of electrons to the area in danger [16] It can alsofunction by transforming undesirable anodic (active) sites ona metalrsquos surface to cathodic (passive) sites via the use of anopposing currentThis opposing current supply free electronsand forces local anodes to be polarized to the potential ofthe local cathodes [18] Cathodic protection is more reliableeffective and economical method for protection of a varietyof pipelines tanks and marine structures including shipshulls and submarines against corrosion Cathodic protectionworks primarily by depressing the natural corrosion potentialof the structure to be protected to a value where it does notcorrode [19 20] Coating alongside with cathodic protectioncan be used together Both of them complement each otherwhere possible such that one can use them in combinationto achieve the optimal economy and protection The coat-ing protects everywhere but at holidays This combinationminimizes the amount of current a cathodic protectionsystem must provide and distributes that current further andmore evenly With undercutting of the coating by corrosionmitigated a coating can last longer [21] However the coatingsystem must be compatible with cathodic protection and thelevel of cathodic protection must not be excessive Thoughnormally compatible coatings may break up due to excessivelevels of cathodic protection This gives way for corrosionto take place at the disbandment area where cathodicprotection currents may not be able to reach Several workshave been carried out by researchers on the inhibition ofmild steel using synergism of different inhibitors [22ndash24]Frunjo Ivusic et al [22] discussed the synergistic inhibitionof mild steel corrosion in seawater by cerium chloride andsodium gluconate Roya Farahmand et al [23] described thesynergistic effect of molybdenum coating and SDS surfactanton corrosion inhibition of mild steel in the presence of35 NaCl Although the synergism of cathodic protectionand plant extract inhibitors are not that common someworks have been done with them Efim Ya Layublinski [24]worked on the synergism in corrosion protection systemwith inhibitors Panpan et al [25] investigated the corrosioninhibition performance of X70 pipeline steel in seawaterusing carboxymethyl chitosan (CMCS) and Na2WO4 at acathodic protection potential of -085v (versus SCE) It wasobserved that as corrosion inhibitors CMCS and Na2WO4show a brilliant synergy for the protection of X70 pipelinesteel in seawater According to Adewole et al [26] thephytochemical antimicrobial and GC-MS of African Nutmeg(Monodora myristica) were analyzed for the phytochemical
components of Monodora myristica From this study it wasobserved that it contains some organic compounds whichhave good potential for corrosion inhibition studies Suchcompounds include alkaloid (1262) saponin (2273mgg plusmn001) tannin (0002mgg plusmn 0002) and flavonoid (0541mggplusmn 0001)
The present study is aimed at investigating the synergisticeffect of Monodora myristica (African Nutmeg) oil extractand cathodic protection on the corrosion inhibition of mildsteel in seawater and 01M sulphuric acid solution using zincsacrificial anode
2 Materials and Methods
21 Samples Collection All the samples used for this experi-ment were sourced locally The seeds of Monodora myristica(African Nutmeg) used were bought from Oja Ota market inOta Ogun State while the mild steel was brought from themild steel dealer in Ota Ogun State Seawater was collectedfrom Elegushi beach in Lekki-Ajah Lagos State
22 Preparation of 01M Sulphuric Acid 533 ml of con-centrated sulphuric acid (assay 98 and density 18) wasmeasured in a 1-liter standard flask and distilled water wasadded to make up the mark The solution was standardizedwith a standard solution of sodium carbonate (Na2CO3)
23 Preparation of Monodora myristica Extract The Mon-odoramyristica fruitswere broken so as to free the seed insideand then the seeds collected were dried in hot air oven at 80∘Ctemperature till all the water content is evaporated Afterthat the sample was weighed using a weighing balance andthe total weight of the sample was 1006456 g To improvisefilter papers (180 mm) were used to wrap the sample and tiedwith threads before inserted into the Soxhlet extractors forrefluxing The solvent used for the extraction was N-Hexaneat a temperature of 60∘C for several hours till all the extractswere collected But the solution containing the extract wasevaporated using the rotary evaporator to evaporate all thesolvent (N-Hexane) from it The oil was recovered as theextract and the volume of the oil extracted was 422273mlThe oil was stored in an amber bottle and kept in a cool dryplace
24 Metal Preparation Themild steel used for this study hasa chemical composition as shown in Tables 1 and 2
The mild steel was mechanically machined using a vicewith a hacksaw and cut into coupons (50 pieces) of dimension(3 cm times 3 cm times 02 cm) while the one used for polarizationmeasurement has dimension 01 cm times 01 cmThese couponswere all polished with series of emery papers up to 800 gritssizes starting from the coarsest to the finest grit size Thezinc sacrificial anodes were used They were also cut intoshape before use The polished coupons were degreased withethanol and allowed to dry before weighing them
25 Weight Loss Measurement The weight losses for thisstudy were carried out by measuring 400 mL of seawater and
International Journal of Corrosion 3
Table 1 Chemical components of mild steel
Elements Si Fe Cu Mn Pb Cr Ni Al P C S Co V present 0018 9936 0034 0189 0006 0025 0031 0052 0013 0142 0012 0045 0016
Table 2 Chemical composition of zinc
Elements Zn Cu Pb Fe Ti Cd Al Sn present 998 007 004 001 lt003 001 001 0003
500 mL of 01M H2SO4 acids respectively into a plastic cupand then the mild steel was subjected to the media For thecathodic protection test the galvanic (sacrificial) method ofprotection system was employed where the zinc sacrificialanodes were used and a copper wire serves as a conductorbetween the metal and the anode with a rod used as supportThese samples were weighed before and after retrieval fromthe corrodent using an analytical balance The weight losseswere all monitored at 3-day interval for the period of 21 daysof exposure After the reading the metalrsquos weight loss orgain (WL) corrosion rate (W) inhibition efficiency () andsurface coverage were calculated using the formulas givenbelow
119908119871 = 119908119894 minus 119908119891 (1)
119862119877 =143700 times 119908119871
785 times 119860 times 119879(2)
119868119864 () =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900times 100 (3)
whereWL is the difference between the initial weight and thefinal weight of the mild steel metals And Wi and Wf are thevalues for the weight loss of the steel without and with theaddition of inhibitors in the solution respectively CR is thecorrosion rate of the mild steel A is the surface area of thesteel and T is the time of immersion The value 785 is thedensity of themild steel while 143700 is the constant used forcalculating corrosion rate inMpy coupon area (cm2) W0 isthe change in weight without the inhibitor and Winh is thechange in weight with the inhibitor
However the surface coverage is a function of the degreeof coverage of the metal surface by the inhibitor moleculesMathematically it is represented as
120579 =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900(4)
where 120579 is the surface coverage
26 Electrochemical Test The linear polarization resistance(LPR) analysis test was carried out using the Autolabpotentiostat-galvanometer Nova 211 system at normal roomtemperature The Linear polarization resistance (LPR) con-sists of three-electrode system which includes the saturatedcalomel reference electrode (SCE) and the working and thecounterelectrode The SCE is the reference electrode andthe working electrode is the mild steel with an exposed
Control1 mL5 mL
10 mL15 mL
minus008minus007minus006minus005minus004minus003minus002minus001
000
Wei
ght L
oss (
g)18 208 10 12 14 164 6 222
Time (Days)
Figure 1 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in seawater
area of 1cm2 for each metal The sacrificial electrode actedas counterelectrode Prior to the measurement 100 mL ofthe corrodent (seawater01M acid) was measured into abeaker before the working electrode was dipped into seawaterand 01M sulphuric acid containing different volumes ofMonodora myristica oil extracts for 15mins until a stable opencircuit potential (OCP)was obtainedTheOCP values startedfrom -01mv and stopped at +01mv at a scan rate of 0001 mvThe values obtained for different parameters during the Tafelplots are shown in Tables 4 and 5
3 Results and Discussion
31 Weight Loss Measurement The plot for the synergis-tic effect of cathodic protection and different volumes ofMonodora myristica oil extract for steel with zinc anode inseawater is shown in Figure 1 It is observed from the plot thatthe weight loss for the cathodic protection and oil extract forsteel with zinc anode decreased with respect to time for free-inhibitor (control) 1 mL and 5mL oil extracts respectively asseen in Figure 1 but for other higher volumes of oil extracts10 mL and 15 mL the weight loss increases with time Thistrend is contrary to the expected outcome of an increase inthe weight loss of mild steel during the active period of mildsteel However the decrease in weight loss against time asshown in Figure 1 was a result of the increase in the initialweight of the mild steel The increase in the initial weightof the mild steel could be a result of possible deposits like
4 International Journal of Corrosion
Table 3 pH values for cathodic protection and different volumes of oil extract for steel with zinc in seawater
Days Control 1 mL 5 mL 10 mL 15 mL0 751 756 696 670 6523 760 695 685 672 6656 757 705 685 628 6119 775 737 708 664 62612 731 726 695 684 64015 745 720 705 692 67518 759 731 717 678 66421 740 680 665 652 645
Table 4 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in seawater environment
Extracts Vol (ml) OCP (V) Ecorr Obs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0517 -0503 0003 0003 22449E-08 31238 -1 -0587 -0604 0002 0003 91358E-08 5664 -306955 -0465 -0453 0002 0002 10141E-08 42661 54810 -0489 -0475 0002 0002 49065E-09 91520 7815 -0620 -0625 0001 0002 47488E-09 83378 788
Table 5 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in 01M sulphuric acid
Extracts Vol (ml) OCP (V) EcorrObs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0532 -0540 0004 0005 17982E-05 52847 -1 -0488 -0484 0003 0002 54309E-07 84987 96975 -0516 -0509 0003 0002 17283E-07 27228 9910 -0494 -0482 0001 0003 14303E-08 27040 999915 -0344 -0392 0005 0009 10058E-10 13271E+07 9999
CaCO3 and Mg(OH)2 on the surface of the steel that is areaction between amild steelrsquos surface and some componentsof seawater
According to Li and Du [27] calcareous deposits willform on the protected steel surface after cathodic protectionin seawater This is due to hydrogen evolution and oxygenreduction reactions
H2O +1
2O2 + 2e
minus997888rarr 2OHminus (5)
2H2O + 2eminus997888rarr 2OHminus +H2 (6)
Due to the production of OHminus the magnesium ions willreact with OHminus and are deposited as brucite of Mg(OH)2 onthe steel surface Furthermore with the change in pH nearthe steel surface the inorganic carbonic equilibrium will beupset leading to the concentration of carbonate ions and theprecipitation of CaCO3
Mg2+ + 2OHminus 997888rarr Mg (OH)2 (7)
Ca2+ + CO3 997888rarr CaCO3 (8)
As these nonconductive deposits progressively cover thesurface the flux of dissolved oxygen from seawater toward
the steel surface is limited In addition the overall rate ofthe cathodic protection reaction (4) decreases leading to areduction in the cathodic current density required and theconsumption of the sacrificial anode [28ndash32] But howeveraccording to Corrosionpedia [33] a calcareous deposit isa layer that consists of calcium carbonate and other saltsdeposited on the substratersquos surface When the surface iscathodically polarized as in cathodic protection this layeris the result of the increased pH adjacent to the protectionsurface Thus from Table 3 it showed the pH values forthe cathodic protection and different volumes of oil extractsfor steel with zinc From this table it is observed thatthe pH values decreased as the volumes of the oil extractincreased This suggests that as the pH of the electrolytedecreased there was a corresponding increase in the acidityor H+ ion concentration of the solution This is presumedto have prompted the dissolution of the calcareous depositpreviously observed on the surface of the steel Consequentlythis situation exposes the cathodic protection system to thesolution thereby activating the oxidization reaction of theanode which on the other hand caused the increase in theweight loss as observed with the 10 mL and 15 mL of the oilextract seen in Figure 1This is the reason cathodic protectionand oil extracts for steel with zinc are not very effective in theprevention of steel in a seawater environment
International Journal of Corrosion 5
2 4 6 8 10 12 14 16 18 20 22
minus10
minus08
minus06
minus04
minus02
00
Time (Days)
Wei
ght L
oss (
g)
Control1 mL5 mL
10 mL15 mL
Figure 2 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in 01M sulphuric acid
For the cathodic protection of steel with zinc in 01Msulphuric acid between the free-inhibitor (control) and the15 mL oil extracts very slight increases in the weight losswere observed though in the negative range The weightloss ranges from -10 in free-inhibitor to 000 in 15 mL oilextracts as shown in Figure 2The cathodic protection and oilextract for steel with zinc in 01M sulphuric acid suggest thecompatibility of the sacrificial anode (Zn) and the oil extractof Monodora myristica It showed that in 01M sulphuricacid the cathodic protection and oil extract of steel withzinc inhibit completely the degradation of steel It indicatedthat the synergism of cathodic protection and oil extract forsteel with zinc inhibited both the anodic and the cathodicside of the reaction forcing the weight to remain at zeroThis means that more electrons were released in addition tothe oil extract helping to protect the mild steel by stoppingcompletely both the oxidation and oxygen reduction reactionof steel
Comparing the above observations in 01M sulphuricacid and seawater it is very clear from all the plots thatthe synergistic effect of cathodic protection and oil extractof Monodora myristica for steel with zinc proves to be thebest corrosion prevention method compared to the cathodicprotection and oil extracts of steel with zinc in a seawaterenvironment
For the inhibition efficiency (IE ) for the synergisticcathodic protection and oil extract ofMonodora myristica forsteel with zinc in a seawater environment it showed that ithas the following efficiencies as shown in Figure 3 From theplots the efficiencies increase as the volumes of the oil extractincrease that is moving from the negative value which issuggested to be due to the effect of the calcareous deposit onthe surface of the steel to the positive value which is also aresult of the dissolution of the deposit However on the otherhand in 01M sulphuric acid the cathodic protection and oilextract for steel with zinc it has an inhibition efficiency of99 at 1 mL and 1028 at 15 mL as observed in Figure 4Thisis similar to the previous work by Aballe [34] who reported
1 mL5 mL
10 mL15 mL
minus140minus120minus100minus80minus60minus40minus20
020406080
100
Inhibi
tion Effi
cienc
y ()
4 6 8 10 12 14 16 18 20 222Time (Days)
Figure 3 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in seawater
2 4 6 8 10 12 14 16 18 20 22Time (Days)
990995
1000100510101015102010251030
Inhibi
tion Effi
ciency
()
1 mL5 mL
10 mL15 mL
Figure 4 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in 01M sulphuric acid
inhibition efficiency greater 100 This result suggests thatthe synergy of cathodic protection and oil extract of steel withzinc in 01M sulphuric acid showed a very strong adsorptionbond between the oil extract molecule and the surface ofthe metal which is also supported by the sacrificial zincanode Hence in 01M sulphuric acid the synergy of cathodicprotection and oil extract of steel and zinc have a very highand good inhibition efficiency when compared to that ofseawater counterpart
32 Linear Polarization Resistance (LPR) Measurement Thelinear polarization resistance plot (Tafel) for the cathodicprotection and oil extract for steel with zinc in both seawaterand 01M sulphuric acid in the absence and presence ofdifferent volumes of oil extract of Monodora myristica isshown in Figures 5 and 6 and their electrochemical parameterobtained by extrapolation of the Tafel line is shown in Tables
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
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Submit your manuscripts atwwwhindawicom
International Journal of Corrosion 3
Table 1 Chemical components of mild steel
Elements Si Fe Cu Mn Pb Cr Ni Al P C S Co V present 0018 9936 0034 0189 0006 0025 0031 0052 0013 0142 0012 0045 0016
Table 2 Chemical composition of zinc
Elements Zn Cu Pb Fe Ti Cd Al Sn present 998 007 004 001 lt003 001 001 0003
500 mL of 01M H2SO4 acids respectively into a plastic cupand then the mild steel was subjected to the media For thecathodic protection test the galvanic (sacrificial) method ofprotection system was employed where the zinc sacrificialanodes were used and a copper wire serves as a conductorbetween the metal and the anode with a rod used as supportThese samples were weighed before and after retrieval fromthe corrodent using an analytical balance The weight losseswere all monitored at 3-day interval for the period of 21 daysof exposure After the reading the metalrsquos weight loss orgain (WL) corrosion rate (W) inhibition efficiency () andsurface coverage were calculated using the formulas givenbelow
119908119871 = 119908119894 minus 119908119891 (1)
119862119877 =143700 times 119908119871
785 times 119860 times 119879(2)
119868119864 () =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900times 100 (3)
whereWL is the difference between the initial weight and thefinal weight of the mild steel metals And Wi and Wf are thevalues for the weight loss of the steel without and with theaddition of inhibitors in the solution respectively CR is thecorrosion rate of the mild steel A is the surface area of thesteel and T is the time of immersion The value 785 is thedensity of themild steel while 143700 is the constant used forcalculating corrosion rate inMpy coupon area (cm2) W0 isthe change in weight without the inhibitor and Winh is thechange in weight with the inhibitor
However the surface coverage is a function of the degreeof coverage of the metal surface by the inhibitor moleculesMathematically it is represented as
120579 =Δ119908119900 minus Δ119908119894119899ℎ
Δ119908119900(4)
where 120579 is the surface coverage
26 Electrochemical Test The linear polarization resistance(LPR) analysis test was carried out using the Autolabpotentiostat-galvanometer Nova 211 system at normal roomtemperature The Linear polarization resistance (LPR) con-sists of three-electrode system which includes the saturatedcalomel reference electrode (SCE) and the working and thecounterelectrode The SCE is the reference electrode andthe working electrode is the mild steel with an exposed
Control1 mL5 mL
10 mL15 mL
minus008minus007minus006minus005minus004minus003minus002minus001
000
Wei
ght L
oss (
g)18 208 10 12 14 164 6 222
Time (Days)
Figure 1 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in seawater
area of 1cm2 for each metal The sacrificial electrode actedas counterelectrode Prior to the measurement 100 mL ofthe corrodent (seawater01M acid) was measured into abeaker before the working electrode was dipped into seawaterand 01M sulphuric acid containing different volumes ofMonodora myristica oil extracts for 15mins until a stable opencircuit potential (OCP)was obtainedTheOCP values startedfrom -01mv and stopped at +01mv at a scan rate of 0001 mvThe values obtained for different parameters during the Tafelplots are shown in Tables 4 and 5
3 Results and Discussion
31 Weight Loss Measurement The plot for the synergis-tic effect of cathodic protection and different volumes ofMonodora myristica oil extract for steel with zinc anode inseawater is shown in Figure 1 It is observed from the plot thatthe weight loss for the cathodic protection and oil extract forsteel with zinc anode decreased with respect to time for free-inhibitor (control) 1 mL and 5mL oil extracts respectively asseen in Figure 1 but for other higher volumes of oil extracts10 mL and 15 mL the weight loss increases with time Thistrend is contrary to the expected outcome of an increase inthe weight loss of mild steel during the active period of mildsteel However the decrease in weight loss against time asshown in Figure 1 was a result of the increase in the initialweight of the mild steel The increase in the initial weightof the mild steel could be a result of possible deposits like
4 International Journal of Corrosion
Table 3 pH values for cathodic protection and different volumes of oil extract for steel with zinc in seawater
Days Control 1 mL 5 mL 10 mL 15 mL0 751 756 696 670 6523 760 695 685 672 6656 757 705 685 628 6119 775 737 708 664 62612 731 726 695 684 64015 745 720 705 692 67518 759 731 717 678 66421 740 680 665 652 645
Table 4 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in seawater environment
Extracts Vol (ml) OCP (V) Ecorr Obs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0517 -0503 0003 0003 22449E-08 31238 -1 -0587 -0604 0002 0003 91358E-08 5664 -306955 -0465 -0453 0002 0002 10141E-08 42661 54810 -0489 -0475 0002 0002 49065E-09 91520 7815 -0620 -0625 0001 0002 47488E-09 83378 788
Table 5 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in 01M sulphuric acid
Extracts Vol (ml) OCP (V) EcorrObs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0532 -0540 0004 0005 17982E-05 52847 -1 -0488 -0484 0003 0002 54309E-07 84987 96975 -0516 -0509 0003 0002 17283E-07 27228 9910 -0494 -0482 0001 0003 14303E-08 27040 999915 -0344 -0392 0005 0009 10058E-10 13271E+07 9999
CaCO3 and Mg(OH)2 on the surface of the steel that is areaction between amild steelrsquos surface and some componentsof seawater
According to Li and Du [27] calcareous deposits willform on the protected steel surface after cathodic protectionin seawater This is due to hydrogen evolution and oxygenreduction reactions
H2O +1
2O2 + 2e
minus997888rarr 2OHminus (5)
2H2O + 2eminus997888rarr 2OHminus +H2 (6)
Due to the production of OHminus the magnesium ions willreact with OHminus and are deposited as brucite of Mg(OH)2 onthe steel surface Furthermore with the change in pH nearthe steel surface the inorganic carbonic equilibrium will beupset leading to the concentration of carbonate ions and theprecipitation of CaCO3
Mg2+ + 2OHminus 997888rarr Mg (OH)2 (7)
Ca2+ + CO3 997888rarr CaCO3 (8)
As these nonconductive deposits progressively cover thesurface the flux of dissolved oxygen from seawater toward
the steel surface is limited In addition the overall rate ofthe cathodic protection reaction (4) decreases leading to areduction in the cathodic current density required and theconsumption of the sacrificial anode [28ndash32] But howeveraccording to Corrosionpedia [33] a calcareous deposit isa layer that consists of calcium carbonate and other saltsdeposited on the substratersquos surface When the surface iscathodically polarized as in cathodic protection this layeris the result of the increased pH adjacent to the protectionsurface Thus from Table 3 it showed the pH values forthe cathodic protection and different volumes of oil extractsfor steel with zinc From this table it is observed thatthe pH values decreased as the volumes of the oil extractincreased This suggests that as the pH of the electrolytedecreased there was a corresponding increase in the acidityor H+ ion concentration of the solution This is presumedto have prompted the dissolution of the calcareous depositpreviously observed on the surface of the steel Consequentlythis situation exposes the cathodic protection system to thesolution thereby activating the oxidization reaction of theanode which on the other hand caused the increase in theweight loss as observed with the 10 mL and 15 mL of the oilextract seen in Figure 1This is the reason cathodic protectionand oil extracts for steel with zinc are not very effective in theprevention of steel in a seawater environment
International Journal of Corrosion 5
2 4 6 8 10 12 14 16 18 20 22
minus10
minus08
minus06
minus04
minus02
00
Time (Days)
Wei
ght L
oss (
g)
Control1 mL5 mL
10 mL15 mL
Figure 2 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in 01M sulphuric acid
For the cathodic protection of steel with zinc in 01Msulphuric acid between the free-inhibitor (control) and the15 mL oil extracts very slight increases in the weight losswere observed though in the negative range The weightloss ranges from -10 in free-inhibitor to 000 in 15 mL oilextracts as shown in Figure 2The cathodic protection and oilextract for steel with zinc in 01M sulphuric acid suggest thecompatibility of the sacrificial anode (Zn) and the oil extractof Monodora myristica It showed that in 01M sulphuricacid the cathodic protection and oil extract of steel withzinc inhibit completely the degradation of steel It indicatedthat the synergism of cathodic protection and oil extract forsteel with zinc inhibited both the anodic and the cathodicside of the reaction forcing the weight to remain at zeroThis means that more electrons were released in addition tothe oil extract helping to protect the mild steel by stoppingcompletely both the oxidation and oxygen reduction reactionof steel
Comparing the above observations in 01M sulphuricacid and seawater it is very clear from all the plots thatthe synergistic effect of cathodic protection and oil extractof Monodora myristica for steel with zinc proves to be thebest corrosion prevention method compared to the cathodicprotection and oil extracts of steel with zinc in a seawaterenvironment
For the inhibition efficiency (IE ) for the synergisticcathodic protection and oil extract ofMonodora myristica forsteel with zinc in a seawater environment it showed that ithas the following efficiencies as shown in Figure 3 From theplots the efficiencies increase as the volumes of the oil extractincrease that is moving from the negative value which issuggested to be due to the effect of the calcareous deposit onthe surface of the steel to the positive value which is also aresult of the dissolution of the deposit However on the otherhand in 01M sulphuric acid the cathodic protection and oilextract for steel with zinc it has an inhibition efficiency of99 at 1 mL and 1028 at 15 mL as observed in Figure 4Thisis similar to the previous work by Aballe [34] who reported
1 mL5 mL
10 mL15 mL
minus140minus120minus100minus80minus60minus40minus20
020406080
100
Inhibi
tion Effi
cienc
y ()
4 6 8 10 12 14 16 18 20 222Time (Days)
Figure 3 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in seawater
2 4 6 8 10 12 14 16 18 20 22Time (Days)
990995
1000100510101015102010251030
Inhibi
tion Effi
ciency
()
1 mL5 mL
10 mL15 mL
Figure 4 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in 01M sulphuric acid
inhibition efficiency greater 100 This result suggests thatthe synergy of cathodic protection and oil extract of steel withzinc in 01M sulphuric acid showed a very strong adsorptionbond between the oil extract molecule and the surface ofthe metal which is also supported by the sacrificial zincanode Hence in 01M sulphuric acid the synergy of cathodicprotection and oil extract of steel and zinc have a very highand good inhibition efficiency when compared to that ofseawater counterpart
32 Linear Polarization Resistance (LPR) Measurement Thelinear polarization resistance plot (Tafel) for the cathodicprotection and oil extract for steel with zinc in both seawaterand 01M sulphuric acid in the absence and presence ofdifferent volumes of oil extract of Monodora myristica isshown in Figures 5 and 6 and their electrochemical parameterobtained by extrapolation of the Tafel line is shown in Tables
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
4 International Journal of Corrosion
Table 3 pH values for cathodic protection and different volumes of oil extract for steel with zinc in seawater
Days Control 1 mL 5 mL 10 mL 15 mL0 751 756 696 670 6523 760 695 685 672 6656 757 705 685 628 6119 775 737 708 664 62612 731 726 695 684 64015 745 720 705 692 67518 759 731 717 678 66421 740 680 665 652 645
Table 4 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in seawater environment
Extracts Vol (ml) OCP (V) Ecorr Obs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0517 -0503 0003 0003 22449E-08 31238 -1 -0587 -0604 0002 0003 91358E-08 5664 -306955 -0465 -0453 0002 0002 10141E-08 42661 54810 -0489 -0475 0002 0002 49065E-09 91520 7815 -0620 -0625 0001 0002 47488E-09 83378 788
Table 5 Electrochemical parameters obtained from the Tafel plots for cathodic protection and different volumes (ml) of oil extract ofMonodora myristica for steel with zinc in 01M sulphuric acid
Extracts Vol (ml) OCP (V) EcorrObs (V) Bc (Vdec) Ba (Vdec) icorr (Acm2lowast 10-5) Polarization Resistance (Ω) IE ()
Control -0532 -0540 0004 0005 17982E-05 52847 -1 -0488 -0484 0003 0002 54309E-07 84987 96975 -0516 -0509 0003 0002 17283E-07 27228 9910 -0494 -0482 0001 0003 14303E-08 27040 999915 -0344 -0392 0005 0009 10058E-10 13271E+07 9999
CaCO3 and Mg(OH)2 on the surface of the steel that is areaction between amild steelrsquos surface and some componentsof seawater
According to Li and Du [27] calcareous deposits willform on the protected steel surface after cathodic protectionin seawater This is due to hydrogen evolution and oxygenreduction reactions
H2O +1
2O2 + 2e
minus997888rarr 2OHminus (5)
2H2O + 2eminus997888rarr 2OHminus +H2 (6)
Due to the production of OHminus the magnesium ions willreact with OHminus and are deposited as brucite of Mg(OH)2 onthe steel surface Furthermore with the change in pH nearthe steel surface the inorganic carbonic equilibrium will beupset leading to the concentration of carbonate ions and theprecipitation of CaCO3
Mg2+ + 2OHminus 997888rarr Mg (OH)2 (7)
Ca2+ + CO3 997888rarr CaCO3 (8)
As these nonconductive deposits progressively cover thesurface the flux of dissolved oxygen from seawater toward
the steel surface is limited In addition the overall rate ofthe cathodic protection reaction (4) decreases leading to areduction in the cathodic current density required and theconsumption of the sacrificial anode [28ndash32] But howeveraccording to Corrosionpedia [33] a calcareous deposit isa layer that consists of calcium carbonate and other saltsdeposited on the substratersquos surface When the surface iscathodically polarized as in cathodic protection this layeris the result of the increased pH adjacent to the protectionsurface Thus from Table 3 it showed the pH values forthe cathodic protection and different volumes of oil extractsfor steel with zinc From this table it is observed thatthe pH values decreased as the volumes of the oil extractincreased This suggests that as the pH of the electrolytedecreased there was a corresponding increase in the acidityor H+ ion concentration of the solution This is presumedto have prompted the dissolution of the calcareous depositpreviously observed on the surface of the steel Consequentlythis situation exposes the cathodic protection system to thesolution thereby activating the oxidization reaction of theanode which on the other hand caused the increase in theweight loss as observed with the 10 mL and 15 mL of the oilextract seen in Figure 1This is the reason cathodic protectionand oil extracts for steel with zinc are not very effective in theprevention of steel in a seawater environment
International Journal of Corrosion 5
2 4 6 8 10 12 14 16 18 20 22
minus10
minus08
minus06
minus04
minus02
00
Time (Days)
Wei
ght L
oss (
g)
Control1 mL5 mL
10 mL15 mL
Figure 2 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in 01M sulphuric acid
For the cathodic protection of steel with zinc in 01Msulphuric acid between the free-inhibitor (control) and the15 mL oil extracts very slight increases in the weight losswere observed though in the negative range The weightloss ranges from -10 in free-inhibitor to 000 in 15 mL oilextracts as shown in Figure 2The cathodic protection and oilextract for steel with zinc in 01M sulphuric acid suggest thecompatibility of the sacrificial anode (Zn) and the oil extractof Monodora myristica It showed that in 01M sulphuricacid the cathodic protection and oil extract of steel withzinc inhibit completely the degradation of steel It indicatedthat the synergism of cathodic protection and oil extract forsteel with zinc inhibited both the anodic and the cathodicside of the reaction forcing the weight to remain at zeroThis means that more electrons were released in addition tothe oil extract helping to protect the mild steel by stoppingcompletely both the oxidation and oxygen reduction reactionof steel
Comparing the above observations in 01M sulphuricacid and seawater it is very clear from all the plots thatthe synergistic effect of cathodic protection and oil extractof Monodora myristica for steel with zinc proves to be thebest corrosion prevention method compared to the cathodicprotection and oil extracts of steel with zinc in a seawaterenvironment
For the inhibition efficiency (IE ) for the synergisticcathodic protection and oil extract ofMonodora myristica forsteel with zinc in a seawater environment it showed that ithas the following efficiencies as shown in Figure 3 From theplots the efficiencies increase as the volumes of the oil extractincrease that is moving from the negative value which issuggested to be due to the effect of the calcareous deposit onthe surface of the steel to the positive value which is also aresult of the dissolution of the deposit However on the otherhand in 01M sulphuric acid the cathodic protection and oilextract for steel with zinc it has an inhibition efficiency of99 at 1 mL and 1028 at 15 mL as observed in Figure 4Thisis similar to the previous work by Aballe [34] who reported
1 mL5 mL
10 mL15 mL
minus140minus120minus100minus80minus60minus40minus20
020406080
100
Inhibi
tion Effi
cienc
y ()
4 6 8 10 12 14 16 18 20 222Time (Days)
Figure 3 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in seawater
2 4 6 8 10 12 14 16 18 20 22Time (Days)
990995
1000100510101015102010251030
Inhibi
tion Effi
ciency
()
1 mL5 mL
10 mL15 mL
Figure 4 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in 01M sulphuric acid
inhibition efficiency greater 100 This result suggests thatthe synergy of cathodic protection and oil extract of steel withzinc in 01M sulphuric acid showed a very strong adsorptionbond between the oil extract molecule and the surface ofthe metal which is also supported by the sacrificial zincanode Hence in 01M sulphuric acid the synergy of cathodicprotection and oil extract of steel and zinc have a very highand good inhibition efficiency when compared to that ofseawater counterpart
32 Linear Polarization Resistance (LPR) Measurement Thelinear polarization resistance plot (Tafel) for the cathodicprotection and oil extract for steel with zinc in both seawaterand 01M sulphuric acid in the absence and presence ofdifferent volumes of oil extract of Monodora myristica isshown in Figures 5 and 6 and their electrochemical parameterobtained by extrapolation of the Tafel line is shown in Tables
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
International Journal of Corrosion 5
2 4 6 8 10 12 14 16 18 20 22
minus10
minus08
minus06
minus04
minus02
00
Time (Days)
Wei
ght L
oss (
g)
Control1 mL5 mL
10 mL15 mL
Figure 2 Variation of weight loss against time for the cathodicprotection and oil extract for steel with zinc in different volumes ofoil extracts in 01M sulphuric acid
For the cathodic protection of steel with zinc in 01Msulphuric acid between the free-inhibitor (control) and the15 mL oil extracts very slight increases in the weight losswere observed though in the negative range The weightloss ranges from -10 in free-inhibitor to 000 in 15 mL oilextracts as shown in Figure 2The cathodic protection and oilextract for steel with zinc in 01M sulphuric acid suggest thecompatibility of the sacrificial anode (Zn) and the oil extractof Monodora myristica It showed that in 01M sulphuricacid the cathodic protection and oil extract of steel withzinc inhibit completely the degradation of steel It indicatedthat the synergism of cathodic protection and oil extract forsteel with zinc inhibited both the anodic and the cathodicside of the reaction forcing the weight to remain at zeroThis means that more electrons were released in addition tothe oil extract helping to protect the mild steel by stoppingcompletely both the oxidation and oxygen reduction reactionof steel
Comparing the above observations in 01M sulphuricacid and seawater it is very clear from all the plots thatthe synergistic effect of cathodic protection and oil extractof Monodora myristica for steel with zinc proves to be thebest corrosion prevention method compared to the cathodicprotection and oil extracts of steel with zinc in a seawaterenvironment
For the inhibition efficiency (IE ) for the synergisticcathodic protection and oil extract ofMonodora myristica forsteel with zinc in a seawater environment it showed that ithas the following efficiencies as shown in Figure 3 From theplots the efficiencies increase as the volumes of the oil extractincrease that is moving from the negative value which issuggested to be due to the effect of the calcareous deposit onthe surface of the steel to the positive value which is also aresult of the dissolution of the deposit However on the otherhand in 01M sulphuric acid the cathodic protection and oilextract for steel with zinc it has an inhibition efficiency of99 at 1 mL and 1028 at 15 mL as observed in Figure 4Thisis similar to the previous work by Aballe [34] who reported
1 mL5 mL
10 mL15 mL
minus140minus120minus100minus80minus60minus40minus20
020406080
100
Inhibi
tion Effi
cienc
y ()
4 6 8 10 12 14 16 18 20 222Time (Days)
Figure 3 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in seawater
2 4 6 8 10 12 14 16 18 20 22Time (Days)
990995
1000100510101015102010251030
Inhibi
tion Effi
ciency
()
1 mL5 mL
10 mL15 mL
Figure 4 Variation of inhibition efficiency against time for thecathodic protection and different volumes of oil extracts for steelwith zinc in 01M sulphuric acid
inhibition efficiency greater 100 This result suggests thatthe synergy of cathodic protection and oil extract of steel withzinc in 01M sulphuric acid showed a very strong adsorptionbond between the oil extract molecule and the surface ofthe metal which is also supported by the sacrificial zincanode Hence in 01M sulphuric acid the synergy of cathodicprotection and oil extract of steel and zinc have a very highand good inhibition efficiency when compared to that ofseawater counterpart
32 Linear Polarization Resistance (LPR) Measurement Thelinear polarization resistance plot (Tafel) for the cathodicprotection and oil extract for steel with zinc in both seawaterand 01M sulphuric acid in the absence and presence ofdifferent volumes of oil extract of Monodora myristica isshown in Figures 5 and 6 and their electrochemical parameterobtained by extrapolation of the Tafel line is shown in Tables
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
6 International Journal of Corrosion
minus065 minus060 minus055 minus050 minus045 minus040
minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35
Log cu
rren
t (iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 5 Variation of potential (E) against log current (A) fordifferent volumes of oil extract and cathodic protection of steel withzinc in seawater
4 and 5 The inhibition efficiency (IE) for this process wascalculated using the mathematical formula [35]
119868119864 () =119868119900 minus 119868
119868119900times 100 (9)
where Io is the corrosion density current measured for mildsteel free-inhibitor and I is the corrosion density currentcontaining the oil extracts respectively The polarizationcurve for the cathodic protection and oil extract for steel withzinc in seawater is shown in Figure 5 and the electrochemicalparameter is shown in Table 4
For the cathodic protection and oil extract of steel withzinc in seawater with different volumes of oil extracts ofMonodora myristica it is observed from the Tafel plot thatthe corrosion current density (Icorr) values at 1 mL aregreater than every other current with a corrosion potential(Ecorr) value that is shifted toward the negative This showsthat the cathodic protection and oil extract of steel withzinc in seawater could not resist the corrosion reactiontaking place on the surface of the metal due to its very lowpolarization resistance (5664Ω) as seen in Table 4 Due to thehigh corrosion currents corrosion potential shifts toward thenegative side and a low polarization resistance the inhibitionefficiency of the oil extract at that volume has a negative value(-30695) which suggests that the metal is not protected asboth the cathodic and anodic reaction are activated therebyincreasing the rate of corrosion at that point Apart fromthat the corrosion current (icorr) decreases as the volumeof the oil extract increases and the polarization resistanceincreases as the corrosion current decreases and also asthe oil extract increases It is also observed that inhibitionefficiency increases as the volume of the oil extract increaseswith values of 548 78 and 788 for 5 10 and 15mL respectively as seen in Table 4 The corrosion potential(Ecorr) values shifted toward the positive except for 1 and
15 mL which tend toward the negative and also alter thevalues of the cathodic and anodic Tafel plots The same trendoccurs with the value of OCP However when comparedto that of cathodic protection and oil extract of Monodoramyristica steel with zinc in 01M sulphuric acid the corrosionpotential (Ecorr) tends to shift greatly toward the positivewhich therefore causes a change in the cathodic and anodicTafel slope as shown in Table 5 Typical Tafel plot showsthat the corrosion current has a maximum value at free-inhibitor and the minimum at 15 mL of the oil extracts asshown in Figure 6 This suggests that it decreases as thevolume of the oil extract increases This leads to an increasein polarization resistance (Ω) as seen in Table 5 A strikingdifference between the cathodic protection and oil extract ofsteel with zinc in seawater and that of 01M sulphuric acid isthat of inhibition efficiency It is observed that the inhibitionefficiency of steel with zinc in 01M sulphuric acid is higherthan that of the seawater counterpart It was shown that ithas values ranging from 100 for 10 and 15 mL of oil extractsto 99 and 9697 for 5 and 1mL respectively as seen inTable 5 The OCP value shows that it is shifted toward thepositive values The change in the cathodic and the anodicTafel slopes data showed that the inhibitor is a mixed-typeinhibitor According to Rigg (1973) only when the changein OCP values is more than 85mv it can be recognized as aclassification evidence of a compound as anodic or a cathodictype inhibitor The OCP values were not anywhere closedto 85mV hence the inhibitor is referred to as a mixed-typeinhibitor
33 Adsorption Isotherm Adsorption characteristics ofMon-odora myristica were studies to understand the mechanismof interaction between the oil extract and mild steel It isa good practice to find out the likely adsorption mode bytesting the experimental datawith some adsorption isothermThus the obtained values were applied to different adsorptionisotherms equations and Langmuir adsorption isothermequation fitted best as shown in Figure 7 for 01M sulphuricacid with an R2 value of 1 unit indicating a good agreementwith the experimental data and with Langmuir adsorptionisotherm
4 Conclusion
For the synergistic effect of cathodic protection and oil extractfor steel with zinc it was observed that in seawater thesynergism was not too effective for the protection of steelwhereas in 01M sulphuric acid there was a great synergismbetween cathodic protection and the oil extracts ofMonodoramyristica which possesses an inhibition efficiency (IE) of10289 at 15mL of the oil extracts For the linear polarizationresistance (LPR) in most of the cases there is a slight shift ofthe corrosion potential (Ecorr) and the open circuit potential(OPC) toward the positive as the volume of the oil extractsincreased thereby causing a change in the cathodic andthe anodic Tafel slopes which showed that the inhibitor isa mixed-type inhibitor And the corrosion current density(icorr) decreases as the volumes of the oil extract increaseFor the adsorption isotherm Langmuir adsorption isotherm
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
International Journal of Corrosion 7
minus065 minus060 minus055 minus050 minus045 minus040
minus100minus95minus90minus85minus80minus75minus70minus65minus60minus55minus50minus45minus40minus35minus30minus25minus20
Log cu
rren
t(iA
cm-2
)
Potential (V)
Control1ml5ml
10ml15ml
Figure 6 Variation of potential (E) against log current (A) for different volumes of oil extracts and cathodic protection of steel with zinc in01M sulphuric acid
y = 09948x + 00421
02468
10121416
0 5 10 15 20V (mL)
V
(mL)
２2= 1
Figure 7 Langmuir isotherm of Monodora myristica on the syner-gism of steel and zinc in 01M sulphuric acid
fitted best for it with an R2 of 1 unit indicating a goodagreement with the experimental data and with Langmuiradsorption isotherm
Data Availability
The data used to support the findings of this study areavailable from the corresponding author upon request
Disclosure
Oladega Soriyan is on sabbatical leave from ObafemiAwolowo University Ile Ife Nigeria
Conflicts of Interest
The authors declare that they have no conflicts of interest
References
[1] H Kumar and Y Vikas ldquoCorrosion characteristics of mildsteel under different atmospheric conditions by Vapour PhaseCorrosion Inhibitorsrdquo American Journal of Materials Scienceand Engineering vol 1 no 3 pp 34ndash39 2013
[2] J G ThomasThe Electrochemistry of Corrosion 2017[3] I A Denison andM Romanoff ldquoCorrosion of galvanised steels
in soilsrdquo Journal of Research of the National Bureau of Standardsvol 49 no 5 pp 299ndash316 1952
[4] M Romanoff ldquoIn Underground Corrosionrdquo Circ 579 USNational Bureau of Standards 1957
[5] E Schashle and G A Marsh ldquoStudy on the corrosive nature ofsoil towards the buried-structurerdquo Materials Protection vol 2p 17 1963
[6] E Levlin ldquoIn Corrosion of water pipe systems due to acid-ification of soil and groundwaterrdquo Tech Rep Departmentof Applied Electrochemistry and Corrosion Science RoyalInstitute of Technology Stockholm 1992
[7] G Doyle M V Seica and M W F Grabinsky ldquoThe role of soilin the external corrosion of cast iron water mains in TorontoCanadardquoCanadian Geotechnical Journal vol 40 no 2 pp 225ndash236 2003
[8] A Rim- rukehand and J K Awalafe ldquoInvestigation of soilcorrosivity in the corrosion of low carbon steel pipe in soilenviromentrdquo Journal of Applied Science Research vol 2 no 8pp 466ndash469 2006
[9] S R B Shamsuri The effect of soil resistivity on corrosionbehaviour of coated and uncoated low carbon steel ME ThesisFaculty of Mechanical Engineering University TechnologyMalaysia 2010
[10] R W Revie and H H Uhlig Corrosion and Corrosion ControlJohn Wiley amp Sons Inc Hoboken NJ USA 2008
[11] J Bhattarai Frontiers of Corrosion Science Kshitiz publkirrtipur Kathmandu 1st edition 2010
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
8 International Journal of Corrosion
[12] J Bhattarai Spectrum an Annual Science Magazine of ChemSAvol 15 Central Department of Chemistry Tribhuvan Univer-sity Kirtipur 2010
[13] P F Anto ldquoPitting corrosion onweld joints of offshore structurejacketsrdquoMaterial Performance vol 39 no 3 p 70 2000
[14] X G Zhang ldquoCorrosion ratios of steel to zinc in naturalcorrosion enviromentsrdquo Corrosion vol 55 8 p 787 1999
[15] RWRevieUhligrsquos Corrosion Handbook JohnWiley Sons INCNew-york 2000
[16] International Standard Organization Corrosion of metals andAlloys Basic Terms and Definitions
[17] G Huang X Lou H Wang X Li and L Xing ldquoInvestigationon theCathodic Protection Effect of LowPressure Cold SprayedAlZn Coating in Seawater via Numerical Simulationrdquo Coatingsvol 7 no 7 p 93 2017
[18] P A Schweitzer ldquoFundamentals of metallic corrosion Atmo-spheric andMedia Corrosion of metalsrdquo in Corrosion Engineer-ing Handbook Taylor and Francis Group pp 8493-8243 ISBNFlorida 2nd edition 2007
[19] I Gurrappa ldquoCathodic protection of cooling water systemsand selection of appropriate materialsrdquo Journal of MaterialsProcessing Technology vol 166 no 2 pp 256ndash267 2005
[20] C A Loto and A P I Popoola ldquoEffect of anode and sizevariations on the cathodic protection of mild steel in sea waterand sulphuric acidrdquo International Journal of Physical Sciencesvol 6 no 12 pp 2861ndash2868 2011
[21] Reclamation Facilities Instructions Standards and TechniquesVolume 4-5 Corrosion and Cathodic Protection US Departmentof the Interior Bureau of Reclamation Colorado Denver 2013
[22] I Franjo L S Olga O C Helana and A Vesna ldquoSynergisticinhibition of carbon steel corrosion in seawater by ceriumchloride and sodium gluconaterdquo Corrosion Science vol 98 pp88ndash97 2015
[23] R Farahmand B Sohrabi A Ghaffarinejad andM R ZamaniMeymian ldquoSynergistic effect of molybdenum coating and SDSsurfactant on corrosion inhibition of mild steel in presence of35 NaClrdquo Corrosion Science vol 136 pp 393ndash401 2018
[24] Y L Efim ldquoSynergism in corrosion protection system withinhibitorsrdquo Paper No 0119 NACE International USA 2001
[25] P Feng K Wan G Cai L Yang and Y Li ldquoSynergistic protec-tive effect of carboxymethyl chitosan and cathodic protection ofX70 pipeline steel in seawaterrdquo RSC Advances vol 7 no 6 pp3419ndash3427 2017
[26] E Adewole B O Ajiboye O O Idris et al ldquoPhytochemicalAntimicrobial and Gc-Ms of African Nutmeg (MonodoraMyristica)rdquo International Journal of Pharmaceutical ScienceInvention vol 2 no 5 pp 25ndash32 2013
[27] C J Li and M Du ldquoThe growth mechanism of calcare-ous deposits under various hydrostatic pressures during thecathodic protection of carbon steel in seawaterrdquo RSC Advancesvol 7 no 46 pp 28819ndash28825 2017
[28] M R Belmonte B V Quiroz M M Madrid A T Acosta J PCalderon and M S Wiener ldquoCharacterization of steel surfaceunder cathodic protection in sea waterrdquo Anti- Corros MethodsMater vol 60 pp 160ndash167 2013
[29] C Rousseau F Baraud L Leleyter and O JeanninGil ldquoCal-careous deposit formed under cathodic protection in thepresesnce of naturalmarine sediments a 12month experimentrdquoElectrochimica Acta vol 54 pp 196ndash203 2009
[30] C Barchiche C Deslouis O Gil S Joiret P Refait and BTribollet ldquoRole of sulphate ions on the formation of calcareous
deposits on steel in artificial seawater the formation of GreenRust compounds during cathodic protectionrdquo ElectrochimicaActa vol 54 no 13 pp 3580ndash3588 2009
[31] A Benedetti LMagagnin F Passaretti E ChelossiM Faimaliand G Montesperelli ldquoCathodic protection of carbon steel innatural seawater Effect of sunlight radiationrdquo ElectrochimicaActa vol 54 no 26 pp 6472ndash6478 2009
[32] S Rossi P L Bonora R Pasinetti L Benedetti M Draghettiand E Sacco ldquoLaboratory and Field Characterization of aNew Sacrificial Anode for Cathodic Protection of OffshoreStructuresrdquo Corrosion vol 54 no 12 pp 1018ndash1025 1998
[33] Corrosionpedia ldquoCalcareous Coatingrdquo httpwwwcorrosion-pediacomdefinition200calcareous-coating
[34] A Aballe M Bethencourt F J Botana andM Marcos ldquoCeCl3and LaCl3 binary solutions as environment-friendly corrosioninhibitors of AA5083 Al-Mg alloy in NaCl solutionsrdquo Journal ofAlloys and Compounds vol 323-324 pp 855ndash858 2001
[35] M S Al-Otaibi A M Al-Mayouf M Khan A A Mousa S AAl-Mazroa and H Z Alkhathlan ldquoCorrosion inhibitory actionof some plant extracts on the corrosion of mild steel in acidicmediardquo Arabian Journal of Chemistry vol 7 no 3 pp 340ndash3462014
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
CorrosionInternational Journal of
Hindawiwwwhindawicom Volume 2018
Advances in
Materials Science and EngineeringHindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Analytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
ScienticaHindawiwwwhindawicom Volume 2018
Polymer ScienceInternational Journal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
Advances in Condensed Matter Physics
Hindawiwwwhindawicom Volume 2018
International Journal of
BiomaterialsHindawiwwwhindawicom
Journal ofEngineeringVolume 2018
Applied ChemistryJournal of
Hindawiwwwhindawicom Volume 2018
NanotechnologyHindawiwwwhindawicom Volume 2018
Journal of
Hindawiwwwhindawicom Volume 2018
High Energy PhysicsAdvances in
Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom
The Scientific World Journal
Volume 2018
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
ChemistryAdvances in
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom Volume 2018
BioMed Research InternationalMaterials
Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
