The effect of molybdenum on the corrosionperformance of stainless steel in chloride-contaminated and carbonated concreteTh...
OutlineOutline1. Introduction : Importance of studying Mo addition on SSfor alkaline media application2. Mo effect on pit ...
Why is it important to study the role of Molybdenum addition onalkaline Media?Why is it important to study the role of Mol...
Objective of this studyObjective of this study- To investigate the role of Mo on localizedcorrosion resistance of differen...
Industrial SS compositionIndustrialMaterialElements (wt. %)C Si Mn Ni Cr Mo Cu N Co S * PREnAustenitic304L 0.02 0.49 0.60 ...
An absence of positive effect of Mo on pitting corrosion resistanceof austenitic stainless steels was confirmed in alkalin...
Addition of Mo in industrial Duplex SSAddition of Mo in industrial Duplex SS+ No effect for austenitic SS (γ)Positive effe...
Addition of Mo in industrial Ferritic SSAddition of Mo in industrial Ferritic SSPositive effect with only 0.8 % of Mo(Mo)(...
Conclusion of industrial SS approachConclusion of industrial SS approach8/21The austenitic SS presented ananomalous behav...
Highly defined composition SS (Laboratory alloys)for concrete experimentsThe only difference between the SS ofeach type is...
Experimental MethodologyExperimental Methodology1- Stainless steel (SS)sample preparation2- SS sample preparation beingemb...
Experimental MethodologyExperimental Methodology5- Ecorr monitoring of reinforced concrete samplesduring their immersion i...
Ecorr monitoring resultsEcorr monitoring resultsAustenitic SSAustenitic SSStrongdecrease ofEcorr12/21Average EcorrWith Mo ...
Ecorr monitoring resultsEcorr monitoring resultsFerritic SSFerritic SSStrongdecrease ofEcorr13/21Average EcorrWith Mo ~ -2...
Ecorr monitoring resultsEcorr monitoring resultsDuplex SSDuplex SSStrongdecrease ofEcorr14/21Average EcorrWith Mo ~ -50mVW...
Austenitic SSAustenitic SSMoeffect15/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after...
Austenitic SSAustenitic SS16/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging i...
Polarization ExperimntsPolarization ExperimntsFerritic SSFerritic SSMoeffectGeneralcorrosion17/21Polarization Experiments ...
Ferritic SSFerritic SS18/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in Na...
Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solutionDuplex SSDuplex ...
Duplex SSDuplex SS20/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl s...
ConclusionConclusionAddition of 3% of Mo increased the crevice corrosion resistance for alllaboratory SS families even for...
Many thanks for yourattentione-mail address: thiago.mesquita@ugitech.com
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THE EFFECT OF MOLYBDENUM ON THE CORROSION PERFORMANCE OF STAINLESS STEEL IN CHLORIDE-CONTAMINATED AND CARBONATED CONCRETE (EUROCORR 2012, paper 1177)

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Due to the increase application of stainless steels as reinforcement in concrete structures, understanding the behavior of these alloys in media that simulate concrete pore water or in the concrete itself is extremely important for the selection of the most suitable alloy. This paper is a contribution to the understanding of the role of Mo in the corrosion resistance in concrete structures contaminated with chloride ions after carbonation. In order to study the role of Mo, samples of ferritic, austenitic and duplex stainless steels were produced in laboratory with controlled levels of Mo. These samples were prepared based on the chemical composition of commercial stainless steels. The samples were immersed in simulated carbonated and noncarbonated concrete pore solutions, both with the addition of 3.5% of sodium chloride. Samples of these steels were also embedded in concrete that was later carbonated and exposed to saline solution. The performance of the steels in concrete was verified through corrosion potential monitoring (several months) followed by electrochemical experiments (anodic polarization). Finally, the optical and electronic microscopy techniques were used to characterize the corrosion attacked surfaces.

Devido ao aumento na utilização de aços inoxidáveis como armadura em estruturas de concreto, o estudo do comportamento dessas ligas, em meios que simulam a água dos poros de concreto ou no próprio concreto, é de extrema importância para a seleção da liga mais adequada. Este trabalho é uma contribuição para a compreensão do papel de molibdênio (Mo) na resistência à corrosão em estruturas de concreto contaminado com íons de cloreto após a sua carbonatação. Para o estudo do papel do Mo, amostras de aços inoxidáveis ferríticos, austeníticos e dúplex foram produzidas em laboratório com níveis controlados de Mo. As amostras foram preparadas com base na composição química dos aços inoxidáveis comerciais. As amostras foram imersas em soluções simuladas de poros de concreto carbonatado e não carbonatado, ambas com adição de 3,5 % de cloreto de sódio. Amostras destes aços foram também incorporadas em corpos de prova de concreto que foi posteriormente carbonatado e exposto a solução salina. O desempenho dos aços inoxidáveis em concreto foi verificado por meio do monitoramento do potencial de corrosão (vários meses), seguido por experimentos eletroquímicos (polarização anódica). Finalmente, as técnicas de microscopia óptica e eletrônica foram utilizadas para caracterizar as superfícies das amostras atacadas (corrosão).

MESQUITA, T.J; PANOSSIAN, Z; ARAUJO, A.; SANTOS, C.A.L; SANTOS, J.V. S.; NOGUEIRA, R.P. The effect of molybdenum on the corrosion performance of stainless steel in chloride contaminated concrete. In: EUROPEAN COROSION CONGRESS, 2012, Turquia. Proceedings... Turquia: EUROCORR 2012.

Published in: Business, Technology

THE EFFECT OF MOLYBDENUM ON THE CORROSION PERFORMANCE OF STAINLESS STEEL IN CHLORIDE-CONTAMINATED AND CARBONATED CONCRETE (EUROCORR 2012, paper 1177)

  1. 1. The effect of molybdenum on the corrosionperformance of stainless steel in chloride-contaminated and carbonated concreteThe effect of molybdenum on the corrosionperformance of stainless steel in chloride-contaminated and carbonated concreteThiago José MESQUITAZehbour PANOSSIAN, Adriana DE ARAUJO, Celia A. LINO DOS SANTOS,Ricardo P. NOGUEIRA, Eric CHAUVEAU and Marc MANTELSeptember 12th2012
  2. 2. OutlineOutline1. Introduction : Importance of studying Mo addition on SSfor alkaline media application2. Mo effect on pit corrosion of SS in alkaline mediaIndustrial approach – Preliminary Studies3. Mo effect on crevice corrosion in concreteLaboratory approach4. Conclusion1/21
  3. 3. Why is it important to study the role of Molybdenum addition onalkaline Media?Why is it important to study the role of Molybdenum addition onalkaline Media? Scarce literature with a focus on the Mo effect on the alkaline media Unexpected results about austenitic SS corrosion resistance Optimization of new lean duplex SS compositions Many applications for alkaline environments:- Concrete Reinforcement- Petrochemical- Chemical- Food processing- Paper and Alkaline industries- etc …2/21
  4. 4. Objective of this studyObjective of this study- To investigate the role of Mo on localizedcorrosion resistance of different stainlesssteel types under alkaline conditions suchas chloride-contaminated and carbonatedconcrete.3/21
  5. 5. Industrial SS compositionIndustrialMaterialElements (wt. %)C Si Mn Ni Cr Mo Cu N Co S * PREnAustenitic304L 0.02 0.49 0.60 11.12 18.29 0.21 0.31 0.03 0.00 9 19.46316L 0.01 0.49 0.73 11.08 16.89 2.17 0.48 0.03 0.25 10 24.53Ferritic430 0.01 0.31 0.30 0.29 16.16 0.05 0.10 0.03 0.02 5 16.80434 0.03 0.39 0.39 0.45 16.17 0.92 0.12 0.05 0.03 23 20.01Duplex2304 0.02 0.41 1.09 4.02 22.30 0.28 0.30 0.15 0.13 4 25.622205 0.02 0.4 1.61 5.45 22.91 2.78 0.22 0.15 0.07 3 34.48Pitting Resistance Equivalent number (PREn) = %Cr + 3.3 %Mo + 16 %N (empirical formula)-Mo is not the only varying element (Ni and Cr)4/21γ structureγ + α structureα structure*ppm
  6. 6. An absence of positive effect of Mo on pitting corrosion resistanceof austenitic stainless steels was confirmed in alkaline media [1, 2][1] Chauveau E., et al,. MEDACHS 08, International Conference in Coastal and Marine Environments, 2008.[2] T. J. Mesquita, et al. Materials Chem. And Phis., 126 (2011) 602.higher values meanbetter steel stabilityAddition of Mo in industrial Austenitic SSAddition of Mo in industrial Austenitic SSΔEpit = Epit(316)-Epit(304)In alkaline environments AISI 304becomes slightly more resistant than AISI316∆Epit < 05/21
  7. 7. Addition of Mo in industrial Duplex SSAddition of Mo in industrial Duplex SS+ No effect for austenitic SS (γ)Positive effect for duplex (α+γ) SSIs there a Mo role on the ferrite phase (α)?OxygenevolutionOxygenevolutionOxygenevolutionMo increases Epit in all conditions(Mo)(Mo)(Mo)6/21
  8. 8. Addition of Mo in industrial Ferritic SSAddition of Mo in industrial Ferritic SSPositive effect with only 0.8 % of Mo(Mo)(Mo) (Mo)7/21
  9. 9. Conclusion of industrial SS approachConclusion of industrial SS approach8/21The austenitic SS presented ananomalous behavoir in alkalineconditions Mo has a clear positive effect inferritic and duplex SS even inalkaline media.
  10. 10. Highly defined composition SS (Laboratory alloys)for concrete experimentsThe only difference between the SS ofeach type is the Mo CONTENTSPREn = %Cr + 3.3 %Mo + 16 %N*ppmαα+γγ 9/21
  11. 11. Experimental MethodologyExperimental Methodology1- Stainless steel (SS)sample preparation2- SS sample preparation beingembedded in concrete3- Two steps of Concrete Carbonation(at 25oC, at 65% of relative humidity andat 2% of CO2)4- Partial immersion of the reinforcedconcrete samples in saline solution(35 g/L of NaCl)10/21After the 2ndstep,the pH was 10
  12. 12. Experimental MethodologyExperimental Methodology5- Ecorr monitoring of reinforced concrete samplesduring their immersion in the chloride solution6- Electrochemical Experiments ofreinforced concrete samples11/21
  13. 13. Ecorr monitoring resultsEcorr monitoring resultsAustenitic SSAustenitic SSStrongdecrease ofEcorr12/21Average EcorrWith Mo ~ -150mVWith out Mo ~ -320mV
  14. 14. Ecorr monitoring resultsEcorr monitoring resultsFerritic SSFerritic SSStrongdecrease ofEcorr13/21Average EcorrWith Mo ~ -200mVWith out Mo ~ -500mV
  15. 15. Ecorr monitoring resultsEcorr monitoring resultsDuplex SSDuplex SSStrongdecrease ofEcorr14/21Average EcorrWith Mo ~ -50mVWith out Mo ~ -220mV
  16. 16. Austenitic SSAustenitic SSMoeffect15/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solution
  17. 17. Austenitic SSAustenitic SS16/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solution
  18. 18. Polarization ExperimntsPolarization ExperimntsFerritic SSFerritic SSMoeffectGeneralcorrosion17/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solution
  19. 19. Ferritic SSFerritic SS18/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solution
  20. 20. Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solutionDuplex SSDuplex SSMoeffectNocorrosion19/21
  21. 21. Duplex SSDuplex SS20/21Polarization Experiments after aging in NaCl solutionPolarization Experiments after aging in NaCl solution
  22. 22. ConclusionConclusionAddition of 3% of Mo increased the crevice corrosion resistance for alllaboratory SS families even for the austenitic ones which presented anomalousresults in the synthetic carbonated pore concrete solution (pH 10).The 23Cr4.6Ni3Mo (EN 1.4462) duplex stainless steel presented thehighest corrosion resistance among all studied materials under the studiedaggressive concrete condition.Almost all of the samples presented crevice corrosion in the metal/resininterface. Therefore, the experimental methodology should be improved inorder to avoid the crevice corrosion and in order to study only the pittingcorrosion.21/21
  23. 23. Many thanks for yourattentione-mail address: thiago.mesquita@ugitech.com

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