J P C L N o v e m b e r 2 0 0 8 39www.paintsquare.com

Continued

trategies and technologies continueto be developed for combating thegrowth of plant and animal life oncoatings applied to ship hulls. These

developments occur within the context of anawareness of the environmental and fuel effi-ciency significance of hull coatings. Recentpapers describing research into three quitedifferent approaches to hull coatings—bio-cide-containing antifouling coatings, foulrelease coatings, and surface treated coat-ings—are reviewed below.These papers weregiven at the JPCL-PCE Marine CoatingsConference (MCC), held in Hamburg,Germany on September 24–25. The MCCwas held in conjunction with SMM: TheShipbuilding, Machine, and Marine TechnologyInternational Trade Fair. Two related papersalso given at the MCC are reviewed in side-bars accompanying this article.

But first, a little background on hull coat-ings and fouling organisms is in order.

Fouling and itsEconomic and Environmental Impact

Barnacles, mussels, tubeworms, sea weedssuch as enteromorpha and ectocarpus, and

other plant life generically referred to as“slime” attach themselves to all types ofcoatings. (They also adhere to uncoated sub-strates such as wood and steel.) The timeneeded to attach varies: some sea weedsadhere in as little as a few hours, while bar-nacle larvae take about 48 hours.1 By andlarge, the fouling does not occur when a shipis in transit at speeds above 4–5 knots; theforce of the moving water strips away thefouling because it has not had enough time tofully adhere to the coating. Consequently,most fouling occurs when a ship is docked.Water temperature and pH, salinity, and flowspeeds affect the degree of fouling. Warmtropical waters, for example, induce morefouling growth.2

The attachment of fouling causes thesevere roughening of a hull surface, creatingincreased drag as the vessel moves throughwater. This drag either slows down the run-ning speed of the ship, or increases the fuelneeded to power the ship to sustain maxi-mum running speed. Operational costs areincreased either way.This increase in costs isfar from insignificant. By some estimates, a

By the JPCL Staff

S

J P C L N o v e m b e r 2 0 0 840 www.paintsquare.com

surrounding a ship hull.The toxins inhibit the growth of foul-ing organisms, essentially poisoning them. Copper oxide andtributyl-tin (TBT) are examples of biocides that have beenemployed in antifouling coatings; the amount of these biocides,

the specific formulation of a coating, and envi-ronmental and other factors all affect the rateat which the biocide is released into the watersurrounding a ship hull. Depending on the ser-vice environment, antifouling coatings haveservice lives of as little as six months.6

Further development of antifouling coatingsoccurred when TBT biocides were formulatedwith polymer chemistry, leading to the cre-ation of so-called “self-polishing” co-polymers(SPCs).The non-biocidal components of thesecoatings, polymer residues, are somewhatwater-soluble after hydrolysis. So not onlydoes the biocide leach into the water, but theother coating components slowly erode aswell, exposing underfilm layers of toxic poly-mer for renewed hydrolysis.The surface of thefilm thus becomes smoother, or polished.Thispolished surface creates less drag, whichenhances fuel efficiency. Some SPCs are notedfor providing as long as a five-year service life.

There are, however, negative environmentalconsequences from the use of biocide-con-

taining antifoulings. Evidence has been gathered throughoutthe globe of the increasing bioaccumulation of tin, copper, andother toxins in fish, crustaceans, and other marine organismsthat do not cause fouling (non-target organisms).7 This creates

Clic

kou

rR

eade

re-

Card

atpa

ints

quar

e.co

m/r

ic

10,000-ton (9,000-tonne) fouling-laden cruiser, after 6 monthsin temperate waters, may use up to 45% more fuel to maintaina speed of 20 knots, compared to a fouling-free vessel.3

In addition to the increased fuel costs, increased fuel con-sumption entails the releaseinto the atmosphere ofgreater amounts of pollutants.This release of pollutants isalso far from insignificant: totalCO2 emissions from the glob-al trading fleet for commercialshipping in the year 2007 hasbeen estimated at 1,120 mil-lion tonnes.4 The differencebetween increased fuel con-sumption and increased CO2emissions is that a ship ownerpays nothing for the latter;there is no tax on the environ-mental damage caused by CO2emissions.5 [Editor’s Note:Thereare, however, regulations cominginto force that restrict other pol-lutants from ship exhaust, e.g.,NOx (nitrogen oxides).]

There are a number of waysthat hull coatings function toreduce fouling and thereby reduce fuel use and environmentalimpact. The technology with perhaps the longest history ofuse is antifouling coatings, which contain biocides (toxins) that,over time, leach into the micro-layer of water immediately

Ziegler Industries is a full service corrosion prevention company withmore than 49 years of experience in industrial painting, insulation,scaffold and sanitation.We have the necessary expertise to completeyour project safely, cost effectively, and with the quality you expectfrom the industries’ leader.

Industrial Services Including:

Maintenance Painting Programs

Shutdown Projects

Scaffold and Insulation

Sanitation

Ziegler Industries,Inc.P.O. Box 189 • #1 Ziegler Industrial Park • Nauvoo, IL 62354

(217) 453-2271 • (800) 42BLAST • FAX (217) 453-6645service@ziegler-industries.com • www.ziegler-industries.com

#1 USWINDTURBINE INDUSTRY INDEPENDENT PAINTING CONTRACTOR

Click our Reader e-Card at paintsquare.com/ric

a seeming paradox—coatings that aid in the reduction of fuelconsumption and the associated air pollution are toxic to non-target organisms in the seas.The old adage applies: it’s hard totell the poison from the cure.The use of antifoulings with TBTas a biocide is now banned; the International MaritimeOrganization (IMO) adopted the International Convention onthe Control of Harmful Anti-Fouling Systems on October 5,2001, and the Convention came into full force on September17, 2008.

Foul-Release CoatingsDevelopments in an alternative technology are discussed inthe paper, “Operational and Environmental Impact of FoulRelease Coatings,” by C.W. O’Leary of International Paint Ltd.,UK.

Foul-release coatings are biocide free; instead, they are for-mulated to create a non-stick surface similar to the inside ofnon-stick cookware. The coating film, by virtue of its very lowsurface energy, is slippery and thus minimizes the ability of

J P C L N o v e m b e r 2 0 0 8 41www.paintsquare.com

Continued

he shipping industry is in themiddle of an energy crisis remi-niscent of the 1970’s, and ownersare busy trying to save energy.

The use of efficient antifouling systemsis one of the main methods to obtainfuel cost savings. Since the tin ban, theuse of silicone foul-release coatingshas been the method of choice. JohnDrew of the Carnival Corporation gavean owner’s perspective of applying sili-cone or foul-release coatings to new-buildings, at the recent MarineCoatings Conference (Hamburg, 24–25September 2008).Carnival Corporation decided to use

foul-release coatings and has a trackrecord of their use on more than twen-ty ships, all coated at repair. For opti-mum savings and performance, how-ever, the question to be answered is,“Do we apply the coatings at newbuild-ing, or on vessels that are already oper-ational (first drydocking)?” The factorsto be considered are cost differences(application and operational); outfitting

issues; delays in delivery of ships,which are very costly; and other fac-tors, such as new antifouling systemsand underwater cleaning options.With a tight schedule, a silicone-

based paint system can be applied inseven days. The following are variousoptions.• Apply at newbuilding. This mightalso be done at the pre-delivery stagebefore completing the vessel.• Apply it at first docking, after about2.5 years of service. This leads to dif-ferent potential fuel savings. Theadvantage is less drag in the water.Most operators would like to apply

the coatings straightaway, but thispractice could lead to delaying thecompletion time of the ship and add toinitial costs. On the other hand, the firstdocking will be a little less expensive,as usually a washdown and sometouchup is all that is required.Postponing the application of the sys-tem to the first docking will extend thisdocking time, compared to applying it

during newbuilding. Missing a singleplanned cruise has a severe cost penal-ty. In addition, the reliability might bereduced due to inferior adhesion to thefirst antifouling layer.Carnival has not considered practical

the option of application after the blockbuilding stage because it is difficult tomove the segments around withoutdamaging the paint. One also has todeal with masking when the next con-struction phase is under way.Alternatively, it could be applied dur-

ing the pre-delivery phase, whereby thehull is launched with sacrificial anodesattached to it. This approach at leastsaves masking.• A further option might also be toapply it to the flat bottom only, aftersweep blasting as a surface pre-treat-ment.There are pros and cons for the ship-

yard and the owner in the alternatives.This comparative study is ongoing.There is no universal solution, no “onesize fits all.”

fouling to adhere. Even when a ship is inactive and foulingattaches to a foul-release-coated hull, the fouling is removed inone of two ways: either by the shear force of moving water asthe ship travels, or by underwater cleaning, which requires sig-nificantly less shear force than needed to remove fouling fromhulls coated with an antifouling coating. The diminished forceneeded to remove the fouling also results in less damage tothe coating, O’Leary points out.

Foul-release chemistry, developed in the 1990s, typically isbased on silicone. O’Leary addresses the next generation offoul-release technology, patented in 2007, based on fluo-ropolymer chemistry. According to O’Leary, this new chem-istry represents a significant improvement over the silicon-based systems: 2% improved fuel efficiency and 2% reducedemissions; and, compared to typical SPC antifoulings, 6%improved fuel efficiency and 6% reduced emissions.

The author attributes the advantages of the new fluo-ropolymer technology to several factors. The average hull

An Owner’s View of Foul-Release Coatings

T

Munkebo Clemco A/S

Smedeloekken 5-7 • DK 5330 Munkebo

Tel: +45 65 97 43 80 • Fax: +45 65 97 47 45

info@munkebo.com • www.munkebo.com

Clemco Industries Corp:One Cable Car Drive • Washington • MO 63090 - 1122Tel: +1 636/239-8100 • info@clemcoindustries.com • www.clemcoindustries.com

Surface CleaningEquipment all over the World

Setting the Standard for

Decades of experience helpMunkebo Clemco create the solutions for decades to come

When you work together with Mun-kebo Clemco, you will experiencethat we base our work on youractual needs. If you know theseprecisely, we see our job to find asolution that exactly fulfils theneeds - no more no less. If you havea more vague idea, we will help todiscover and define your needs.

Abrasive Transport and RecoveryEquipmentVacuum and/or mechanical.

Ventilation Systems Portable and stationary.

DehumidifiersAdsorption or refrigirated.

Blast Room Design & InstallationEquipment for complete blast- andpaint room installations.

Call us and benefit from decades ofexperience...

Click our Reader e-Card at paintsquare.com/ric

J P C L N o v e m b e r 2 0 0 8 43www.paintsquare.com

Continued

Clickour

Reader

e-Cardatpaintsquare.com

/ric

DeFelsko Corporation802 Proctor Ave., P.O. Box 676 • Ogdensburg, NY 13669Phone: 315-393-4450 • Fax: 315-393-8471 • Email: techsale@defelsko.com

The Measure of Quality

Call us or check our website for details1-800-448-3835 – www.defelsko.com

Measures adhesion of coatings to metal, masonryand other substrates

� Internal memory stores maximum pull-off pressure, rate of pull, testduration and dolly size for up to 200 pulls

� Pull Rate Indicator - allows operator toeasily monitor and adjust the rate of pull inaccordance with international test methods

� Self-aligning dolly enables accurate measurements on smooth or uneven surfaces

� Weatherproof, dustproof and shockproof

THE DIGITAL EVOLUTION New

PosiTest®Pull-Off Adhesion Tester

roughness (AHR) is singled out as critical. According toO’Leary, measurements performed on hundreds of vesselsindicate an AHR of 125 microns (5 mils) for SPC antifouling-coated hulls; an AHR of 100 microns (4 mils) for silicon-basedfoul-release-coated hulls; and 75 microns (3 mils) for a fluo-ropolymer-based foul-release-coated hull.

The low surface energy advantages of fluoropolymer foul-release coatings are attributed by the author to theiramphiphilic properties. That is, these coatings are bothhydrophobic (repelled by water) and hydrophilic (attracted towater). Their amphiphilic nature is significant because somemarine fouling organisms have a hydrophobic nature, whileothers have a hydrophilic nature. The amphiphilic surface ofthe fluoropolymers enables the coatings to minimize thechemical and electrostatic adhesion between the surface anda wide range of foulings.

The resistance of these new coatings to slime build-up isalso reported to be 50% greater than the resistance of silicon-based foul release coatings.

The author, in conclusion, projects a mean savings compari-son between these new coatings and an SPC antifouling for aVery Large Crude Carrier (VLCC): over a five-year period, a

savings of over 9,300 tons of fuel (USD 2.8 million based on aprice of $300 per ton); and a reduction in CO2 emissions ofaround 12,000 tons.

Antifoulings RevisitedEivind A. Berg presents a quite different perspective on foulingreduction in his paper, “The Environmental Trade-Off.”According to Eivind, the leaching of biocides from antifoulingcoatings presents far less of an environmental threat than thegreenhouse gases (GHGs) emitted from commercial shipping.

In Berg’s analysis, hull smoothness imparted by foul-releasecoatings is diminished during service due to microbial growthand slime attachment. Regular cleaning of such surfaces isrequired to prevent this fouling and regain acceptable fueleconomy. Therefore, he concludes, state-of-the-art biocide-based antifoulings outperform foul-release coatings in terms ofreduced fuel use and GHG emissions. By “state-of-the-art,” theauthor is referring to biocides currently used in antifoulings,subsequent to the IMO’s TBT ban.These biocides are not list-ed or detailed in the article but are noted to be documentedas environmentally acceptable.Two criteria are named for this

Click our Reader e-Card at paintsquare.com/ric

C

J P C L N o v e m b e r 2 0 0 844 www.paintsquare.com

Clic

kou

rR

eade

re-

Card

atpa

ints

quar

e.co

m/r

ic

According to the author, hull roughnessdefines environmental impact. In light of this,he says that foul-release coatings are softerthan antifoulings and are more easily damagedby anchor chains, quays, and other ship equip-ment. Foul-release coatings are also more dif-ficult to repair and maintain, the author says.

Surface Treated CoatingsYet another strategy for dealing with foulingon hull coatings has been recently developed.This strategy is described in “Surface TreatedCoatings and Ship Hull Performance,” writtenby B. Van Rompay of Hydrex NV/SubseaIndustries NV. Surface treated coatings (STCs)are biocide free. They are formulated to bedurable and to undergo regular underwaterpower-tool cleaning and conditioning through-out the service life of the coating, without theneed for reapplying the coating.

The conditioning aspect of the strategy is

Continued

acceptability: the biocide, once leached fromthe coating, must degrade or deactivate inhours or days to become non-toxic; and thebiocide must not create the potential forbioaccumulation in organisms or foodchains.

Berg also discusses the transport of hull-attached, invasive, non-indigenous speciesfrom one global region to another.Environmental hazards are associated withthis transport; take, for example, the damag-ing translocation in the 1980s of zebra mus-sels from the Caspian Sea into the U.S.Great Lakes. The author makes two pointsregarding the transport of invasive species:first, that it is not regulated nor taken intoaccount in assessing environmental impact;and second, that antifoulings outperformfoul-release coatings in the prevention ofthis transport. [Editor’s Note:Transport of inva-sive species via ballast water exchanged isbeing regulated.]

Click our Reader e-Card at paintsquare.com/ric

J P C L N o v e m b e r 2 0 0 846 www.paintsquare.com

designed to improve the surface charac-teristics of the coating, while the cleaningaspect is designed to remove any fouling inthe early stages of development.Therefore, hull smoothness is of para-mount importance for STCs: it is the pri-mary factor in reducing fuel consumptionand hence reducing GHG emissions. Agraph in the paper demonstrates that,compared to a newly applied STC, hullroughness actually decreases after thecoating has been in service and has thenbeen cleaned and conditioned.The author

further notes that there is now a patent-ed technique that combines the condi-tioning and cleaning operations of an STC,thereby reducing maintenance costs.

One commercially available STC for-mulation is described in the paper—avinyl ester with a high concentration ofembedded glass flakes.This STC, appliedat high film thickness, is reported to havegood anti-corrosive properties and to beapproved as a superior-grade ballast tankcoating, the application for which it wasoriginally designed. Furthermore, the

author cites tests that indicate that aftermore than 500 cleanings of the sameSTC-coated surface, smoothness isimproved compared to the hull as origi-nally coated.

Van Rompey says that another advan-tage of STCs over foul-release andantifouling coatings is the STCs’ superiorremoval during cleaning of smaller foul-ing, e.g., protozoa and spores of algae.After cleaning, foul-release and antifoul-ing coatings are reported to have morecrevices than STCs; smaller foulings takeshelter in these crevices, increasing drag.According to the author, it has also beendemonstrated that removing foulingfrom a vessel without reapplying anantifouling paint increases the suscepti-bility of the surface to new fouling.

The author also describes an ongoingEU-funded research project that assess-es the economical and environmentalbenefits of applying STCs. According tothe author, other testing also indicatesthat the underwater conditioning ofSTCs, which releases fine particulatematter into seawater, is an environmen-tally safe process.

FurthermoreFor more information on the papersreviewed, contact JPCL’s Brian Goldie—email: brianpce@aol.com.

Notes1. Clive H. Hare, Protective Coatings:

Fundamentals of Chemistry andComposition, Technology Publishing(Pittsburgh, PA), 1994, p. 486.

2. Hare, p. 486.3. Hare, p. 485.4. Review of MARPOL Annex VI, IMO,

Sub-Committee on Bulk Liquids andGases 2007.

5. Berg, Eivind A., “The EnvironmentalTrade-Off,” paper presented at theShipbuilding, Machinery, & MarineTechnology International Trade Fair(SMM; Hamburg, Germany) 2008.

6. Hare, p. 486.7. Hare, p. 488.

ull performance is critical forboth fuel economy and fuel emis-sions control. The ability to accu-rately monitor fuel economy and

emissions was the subject of a presen-tation, “Hull Performance Monitoring: ATool for Fuel/Emissions Management,”by Daniel Kane, Propulsion Dynamics,also given at the Marine CoatingsConference.The speaker presented a monitoring

system that has been in use for aboutfive years. The system gives a precisespeed-through-water analysis and thecorresponding fuel consumption. Thefactors affecting hull performance are• age of ship/ time out of dock;• time in port;• service speed;• water temperature;• fouling; and• loading conditions.All ships have “performance monitor-

ing systems,” and all owners say theyare aware of their fuel consumption perday. The factors affecting consumptionthat owners can control are coatingselection during newbuilding, drydock-ing interval, hull pre-treatment andcoating at drydocking and a mainte-nance program. The speed log, howev-er, isn’t measured relative to the waterconditions. Wind, and, to a certain

extent, the fuel itself and the loadingconditions are all parameters that influ-ence the sailing characteristics. By mak-ing use of the hydrodynamic techniquein the proprietary monitoring system,these and variables like trim and foulingcan be monitored. The problem is thencorrecting the performance data intoactual speed through the water. Forexample, 60% power can lead to any-thing between 19 and 26 knots.By using the performance-monitoring

program, examples were given to show• how polishing the propeller can reducedrag by up to ten percentage points;• that cleaning the hull led to reducingthe fuel consumption from 190 to 170tons a day in one instance;• that a ship that anchored for fourweeks used up nine tons a day morethan before anchoring; and• different antifouling coatings can becompared for effectiveness.By analyzing all the operational vari-

ables for a vessel, an accurate picture ofhull performance (drag) can beobtained, and the optimum clean-ing/coating cycle can be predicted togive maximum fuel savings and mini-mum emissions. It has been calculatedthat typical average fuel savings in themerchant fleets worldwide are about5–15 tons a day.

Monitoring Hull Performance

H