Repassivation Behavior Of UNS N06022 In Chloride-Containing Solutions

摘要

This paper evaluates a potential degradation process due to sulfur segregation that might occur on UNS N06022 waste package material in a geologic repository setting. To evaluate susceptibility to sulfur-enhanced corrosion, the repassivation behavior of UNS N06022 was investigated in sulfur-containing chloride solutions using a scratch technique. Once the passive film was disrupted by scratching, anodic current increased abruptly to the peak current and thereafter decreased. With increasing potential, peak current increased and thickness of the reformed passive film increased. The addition of 0.01 M Na_2S yielded nearly identical results as the sulfur-free cases. In simulated concentrated water containing 0.01 M Na_2S, repassivation commenced immediately after scratching. However, an increase of the concentration to 0.1 M Na_2S at 22 °C or increase of temperature to 60 °C causes a decrease in peak current. Results indicated that UNS N06022 can repassivate in a relatively short period in sulfur-containing solutions.