Molybdenum surface enrichment and release during transpassive dissolution of Ni-based alloys

By Henderson, Jeffrey D.; Li, Xuejie; Shoesmith, David W.; No
Published in Corrosion Science 2019

Abstract

The role of alloyed Mo during transpassive dissolution of four commercially available Ni-based alloys in neutral chloride solution was investigated by atomic emission spectroelectrochemistry. Time-resolved dissolution rates of Ni, Cr, Mo, and Fe were obtained as a function of applied potential. Mo enrichment occurred at the transpassive potentials and redissolved when the potential returned to the passive domain. These results suggest a mechanism of Mo enrichment and release that could play a significant role in repassivation in initially neutral electrolytes such as occurs during crevice corrosion. It is proposed that Mo precipitation and redissolution are driven by local pH changes.

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