The study of passive layers grown on AISI 316 stainless steel in two model solutions, saturated Ca(OH)2 and cement extract (CE) solution, show that each solution simulates the concrete pore environment in a different way. A more resistant passive layer is formed in CE solution due to its distinctive composition, homogeneity, thickness and porosity. The CE-exposed sample withstood several hours of cathodic polarization before the characteristic cyclic voltammetry peaks of the non-passivated AISI 316 reappeared. This is in contrast to the saturated Ca(OH)2-exposed sample, which showed the characteristic CV peaks after several minutes of cathodic polarization. XPS spectra of the passive layer formed in saturated Ca(OH)2 indicate that the amount of Ca is as much as 10 times larger than that in the passive-layer formed in the CE solution. Films formed in CE solution contained Si and S, which are part of the cement mixture composition. Topographical dissimilarities in the passive films are also found in the AFM and optical microscopy images. The passive layer formed in CE solution is homogeneous and covers the metal surface completely. The film formed in saturated Ca(OH)2 is rough, crystalline, and nonhomogeneous.
The differences in the composition and electrochemical behavior of passive layers formed on AISI 316 in saturated Ca(OH)2 solution or CE model solution suggest that CE solutions are superior for simulating concrete pore environments and that CE solutions create a more resistive passive film. In addition, passive films formed without polarization were superior to films formed on AISI 316 under anodic polarization.
Journal of Electroanalytical Chemistry
College of Arts and Sciences
Department of Chemistry
corrosion, cement, stainless steel, cyclic voltammetry, AFM, passivation
Veleva, Lucien; Alpuche-Aviles, Mario A.; Graves-Brook, Melissa K.; and Wipf, David O., "Comparative cyclic voltammetry and surface analysis of passive films grown on stainless steel 316 in concrete pore model solutions" (2002). College of Arts and Sciences Publications and Scholarship. 35.