Shigeo Ohashi

The Effects of Environmental Factors on Stress Corrosion Cracking of JIS STS 42 Carbon Steel in High Temperature Water

The present study has been undertaken to determine the effects of environmental factors that promote stress corrosion cracking (SCC) of JIS STS 42 carbon steel in high temperature water, and to better understand the SCC mechanism. SCC tests were conducted at temperatures of 423 to 563K in water containing 0.1 to 8ppm of oxygen using the slow strain rate test technique (SSRT). Test results indicated that transgranular SCC was observed at temperatures above 473K and the susceptibility to SCC increased with increasing temperature. The critical dissolved oxygen (DO) concentration for giving SCC initiation was approximately 0.2 ppm and increasing the DO concentration resulted in a great extent of SCC. It was confirmed that SCC behaviors are closely related with properties of oxide film and cracks nucleate from corrosion pits. SCC mechanism for carbon steel in high temperature water is discussed in relation to pitting corrosion.