Post on 02-Jun-2018
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Electrochemical techniques forpainting evaluation for protection
reinforced concrete against
corrosion
Adriana de Araujo
Support:FAPESP
Zehbour Panossian
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Electrochemical techniques:
Corrosion potential and corrosion
current density
Electric contact bet!een electrodes:
"oisture of the concrete
Test specimen
#or$ing electrode
%eference electrode
Counterelectrode
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&arnishes
'o!
permeability
'o!
conductivity
film established in the
surface
Test specimen
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Electrochemicaltechniques
moisture of the concreteat the regionof the electrodes through the plastic
tube(for reference electrode)
Test specimen
Reference electrode and counter-
electrode embedded in concrete ithmeasurementsin !our stretch
displa!ed
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" corrosion potential(
" polari)ation resistance and
corrosion current density
%einforced concrete specimen
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" mass variation(
" carbonatation depth(
" depth and * thechloride(
" film adherence(
" film visual inspection+
Test specimen , no bar
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" number and dimensions of the test
specimen(
" concrete proportion(
" protetion: test specimen edges and
electrodes extremeties(
" concrete consolidition(
" surface finishing+
Exposition to agressive environments
Achievement of the companions tests
Test specimen
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-ponge .for avoiding thepenetration of the cement past
and aggregates/
Protection painting(bars extremities/
Cupperbar
Carbon
steelbar
Plas
tic
tube
Test specimen bar
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Potentostat PA% 201 A
%eference eletrodeSodium sulfate
(10%)Electrolyte solution
#or$ing electrode Steel carbon bar
Saturated Calomel
Parcial painting removed
Electrochemical techniques
ntroducting electrolyte
solution
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Workingelectrode
Reference
eletrode
Corrosion potential
Active or passivestate
Electric potential
difference bet!een
carbon steel and
satureted calomel
Automatic:
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ounter-electrode
Corrosion current density
Ecorr
'inear polari)ation curve(Ecorr#$ m%& scanning speed #$ m%'s)
Tafel constants
Constants 3 .also for reference/
%p .also obtained in the besttangent slop of the curve4 aroundthe Ecorr/
corr .also by manual results/
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Concrete proportion: interference in the results
Cure: insufficient
5inishing: failure in the concrete execution
Elements embebed: infiltration .Cl test/
Should use a/c ratio0,!
Should stabili"e the mass of the
concrete
#ust im$roe theconsolodation
#ust increase theadherence (change the$aint t&$e)
%esultados , test specimen
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Conclusion , test specimen
The test specimen is adequate+++
+++as long as it is !ell executed4 cured4
painted and the electrodes !ere protected
and adherent to the concrete
'''nevertheless in highly aggressive
atmosphere .Cl/ the adherence of the
leaded elements has to be improved
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CO2
exposition
Conclusion, Electrochemical techniques
he corrosion $otential is the best test for thearnish ealuation, although it is recommendedthat it is carried out ith another test(carbonation de$th)
number* ! s$ecimens
he color of the concrete changed (b&$+ test) after the corrosion asdetected
Corrosion current densit& is onl& usefulfor further studies more com$le
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he corrosion $otential can be obtained together
ith profile chlorates!hich is the best test forarnish ealuation
ctie state occurs after high % chlorateshae been detected
Corrosion current densit& is notre$resentatie of $itting corrosion
number* 10 s$ecimens
Conclusion, Electrochemical techniques
Cl exposition
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'''has the best $ro$erties and
the best $erformance$rotection barrier forconcrete structures against
C. and Cl-
e$osition
Conclusion varnish
The polyurethane varnish+++
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Acrylic:
CO2 exposition
%ecently applied film4 1 coats4 leaded to protection
such as the aged polyurethane
%ecently applied film in 2 coats and aged film4 2 e
1 coats4 didn6t protect the concrete.!as similar to
the specimen !ithout painting/
%ecently applied film4 2 and 1 coats4 leaded tobetter protection
Agedfilm4 2 and 1 coats4 is less efficient than the
ne! one .the protection !as similar to the recentapplied acrylic4 1 coats/
Polyurethane:
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%ecently applied film and aged film4 2 e 1 coats4didn6t protect the concrete.!as similar to the
specimen !ithout painting/
%ecently and aged applied film 4 2 and 1 coats4
leaded to better protection
he aging lm didnt reduce itse2cienc& such as in C. e$osition
polyurethane:
Acrylic:
Cl exposition
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end
Than$s for your attention
Than$s 7ehbour Panossian
Than$s 5APE-P