Mechanism of localized corrosion in crevice of stainless steel in high temperature and high purity water

Soma, Yasutaka   

Commemorative speech for "The Award of JSCE for young researcher" of Japan Society of Corrosion Engineering on May 21st 2020, entitled "Characterization of the mechanism of localized corrosion in the crevices of stainless steel in high-temperature, high-purity water" will be made. In this study, we conducted followings: (i) Corrosion test of Type 316L stainless steel to analyze susceptibility to localized corrosion within a crevice in 561K high purity water, and (ii) Develop a sensor system to measure the solution conductivity in a crevice and study relationship between crevice water chemistry and the localized corrosion. These studies were done for the purpose of clarifying the mechanism of stress corrosion cracking (SCC). It was shown that Type-316L stainless steel is susceptible to intergranular corrosion inside the crevice. The developed sensors detected very high solution conductivity in the vicinity of the intergranular corroded area indicate highly corrosive environments were formed in crevice with small gaps. This system can be applied to clarify the mechanism of corrosion related failure, such as SCC, and is expected to contribute to the safety improvement of nuclear reactors.