Intergranular stress corrosion cracking (SCC) mechanism in sensitized stainless steel (Type 304) was investigated experimentally. A tetra-thionic potassium (K2S4O6) chemical solution was used to mimic polythionic acid SCC which the most aggressive SCC type. During the SCC test, the steel specimen was subjected to three-point bending with constant strain at room temperature, and simultaneous monitoring of acoustic emission and corrosion potential were employed to monitor SCC initiation and progression. At the early stage, transient phenomenon of local anodic dissolution was observed. Upon initiation of SCC, passivation film fracture and dissolution of metal at specimen surface take place. Through microscopic observation of SCC tip, it was found that the SCC tip advanced along the grain boundary with further mechanical loading. This suggested that the stress component plays a significant role of SCC propagation, in addition to the effect of the localized metal dissolution along Cr-depleted grain boundaries.
We would like to thank Professor Mikio Tekemoto (Aoyama Gakuin University, Kanmeta Engineering Co., Ltd.) for his guidance. The work of A.Y. is supported in part of Grant-in-Aid for Young Scientist of (B) (No. 22760077) of the Ministry of Education, Culture, Sports, Science and Technology, Japan, and Research Grant for Science and Technology of SUZUKI Foundation. The work of X.C. is supported by the National Natural Science Foundation of China (11172231), the World Class University program through the National Research Foundation of Korea (R32-2008-000-20042-0), and the National Science Foundation (CMMI-0643726).