The long-term integrity of containers for the disposal of high-level nuclear waste in the absence of environmental conditions leading to localized corrosion and stress corrosion cracking is based on the assumption that passive dissolution of Alloy 22 is the dominant mechanism. Corrosion rate measurements under passive and transpassive conditions were performed as a function of temperature, solution pH, and chloride concentration. Analyses of solutions using capillary electrophoresis and the corrosion product deposit using SEM-EDS were performed in order to determine if dissolution was stoichiometric or if preferential dissolution of certain alloying elements was favored. Preliminary measurements suggest that under passive conditions, the dissolution rate is low and stoichiometric. Modeling of passive film dissolution also suggests that while preferential dissolution can occur in the short term, long-term dissolution is likely to be stoichiometric.
Keywords: Alloy 22, High level waste, passive corrosion, passive film chemistry, capillary electrophoresis