Mechanisms of Intergranular Attack and Stress Corrosion Cracking of Alloy 600 by High-Temperature Caustic Solutions Containing Impurities: Final Report

摘要

The mechanisms of intergranular attack (IGA) and intergranular stress corrosion cracking (SCC) of Alloy 600 are investigated in high temperature sodium hydroxide environments contaminated with impurities such as carbonate, sulfate, silicate, magnetite, and chromic oxide. Results show that caustic alone can cause both IGA and SCC. The effects of electrochemical potential, stress, time, temperature and the metallurgical state of Alloy 600 on the IGA and SCC are discussed. It appears that both IGA and SCC are manifestations of a general intergranular failure process. In the presence of adverse potential, stress, strain rate and temperature, the slower IGA process is generally replaced by the faster SCC process. (ERA citation 12:041300)