Localized Corrosion Susceptibility of Alloy 22 in Chloride Solutions: Part 2—Effect of Fabrication Processes

Abstract

The effect of fabrication processes on the localized corrosion susceptibility of Alloy 22 ([UNS N06022] 56Ni-22Cr-13.5Mo-3W-4Fe), a candidate container material for the disposal of high-level nuclear waste in the proposed repository at Yucca Mountain, Nevada, was assessed in chloride-containing solutions at temperatures ranging from 60°C to 95°C. The results of tests covering a range of metallurgical conditions, including as-welded, welded plus solution-annealed, and thermally aged materials, were compared with those for the as-received mill-annealed alloy. The localized corrosion susceptibility of Alloy 22 was determined by comparing the crevice corrosion repassivation potentials with corrosion potentials measured in separate tests. The crevice corrosion susceptibility was found to be dependent on temperature, chloride concentration, and the nitrate-to-chloride molar concentration ratio. Welding and short-term thermal aging decreased the localized corrosion resistance of Alloy 22 compared with the mill-annealed material.