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Improvement of Passivity of Fe - xCr Alloys (x < 10%) by Cycling Through the Reactivation Potential

Classically 13% Cr is required for stable passivity of steel in acidic and neutral solutions. Some authors (Mansfeld, Fujimoto) have published potential cycling procedures that generate thick Cr-rich films. Fujimoto cycles right to the transpassivity potential and back in H2SO4 solution. Our idea is to work close to the reactivation potential where the passive film (Fe2O3) is reductively dissolved to
Fe2+. While using an equimolar acetate buffer (pH 4.7), we have
obtained new insights into the reactivation process. It is under a kind of thermodynamic control, in that the film cannot be reduced, and the metal cannot be dissolved, faster than would exceed the equilibrium concentration of Fe2+ at the electrode surface. Reductive dissolution leads to gel-like Cr-rich film, but Fe dissolution occurs through it, if formed in a single step. However alternating formation and reductive dissolution of a Fe-rich film assist the formation of a more robust Cr-rich film

Identiferoai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/17233
Date26 February 2009
CreatorsUlaganathan, Jaganathan
ContributorsNewman, Roger C.
Source SetsUniversity of Toronto
Languageen_ca
Detected LanguageEnglish
TypeThesis
Format1673633 bytes, application/pdf

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