The effect of Cr and Ni on Stress Corrosion Cracking (SCC) susceptibility was studied in non-sensitized materials under simulated BWR condition. SCC tests were conducted by creviced 4 bent beam test as static strain method, and Slow Strain Rate Test (SSRT) as dynamic strain method. Cr affected markedly to prevent SCC in both SCC tests. Ni was effective to reduce SCC susceptibility under the dynamic strain test, however, not clear to affect SCC susceptibility under the static strain test. The effect of Cr was discussed for corrosion resistant film by examining strain electrode behavior and corrosion products. With increasing the Cr content in material, the repassivation behavior was improved and Cr concentration in inner side of corrosion product increased. These results suggest that Cr affects to suppress SCC due to improve corrosion resistance by Cr concentrated corrosion film.
A new mechanism of atmospheric corrosion was proposed for silver in H2S-NO2-SO2-Cl2 environments. Hydrogen sulfide is oxidized by nitrogen dioxide to form reduced sulfur. The chemical reaction for silver was worked out by using the generated reduced sulfur. After the generation reaction of reduced sulfur, the electrochemical reaction was worked out by using the surplus hydrogen sulfide or the nitrogen sulfide. A novel estimation equation of the corrosion rate for silver was proposed as a function of both pollutant concentration and temperature-humidity. By using the equation, the experimental data in published papers was able to be estimated by a factor of two.