The Passivation of Ni-Cr-Mo Alloys: Time Resolved Enrichment and Dissolution of Cr and Mo during Passive-Active Cycles

The enrichment and dissolution of Cr and Mo were monitored as a function of time during potentiostatic active passive cycles and during the spontaneous passivation of a Ni-Cr-Mo alloy (Hastelloy C-22) in 2 M H2SO4. Atomic emission spectroelectrochemistry was used to directly measure the elemental dissolution rates of the alloy components in real time, and combined with a mass balance, the Cr and Mo enrichments associated with the passive film...