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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