Localized Corrosion and Repassivation Behavior of Ni600 and SS304 Under Conditions Relevant to SCC

RIP2025-00112: It is well-known that Ni alloy 600 presents higher resistance to stress corrosion cracking than stainless steel 304 in chloride-containing environments. To explore potential electrochemical differences between the two alloys, their localized dissolution kinetics and repassivation behavior were examined under pit and crack like conditions. Downward potential scans at constant temperature were performed on 1D pit samples to evaluate metal dissolution kinetics. Additionally, potentiostatic experiments with decreasing temperature were conducted to identify the critical conditions—potential, temperature, and pit depth—at which each alloy repassivates. The results indicate that alloy 600 exhibits slower activation-controlled dissolution kinetics compared to stainless steel 304. However, alloy 600 remains active under less aggressive conditions, such as lower temperatures, while stainless steel 304 demonstrates a higher tendency for repassivation. This repassivation behavior does not directly correlate with the observed differences in SCC susceptibility. To deepen the understanding of these materials' behavior under SCC conditions, density functional theory (DFT) calculations were employed.