H2o2 Humid Air Radiolysis-induced Corrosion of Carbon Steel - Stainless Steel Welds

Abstract

Carbon steel and 304L stainless steel are utilized in CANDU® nuclear reactors, and in the end-shield region are welded to each other using 309 stainless steel. Humid air radiolysis in this region produces both HNO₃ and H₂O₂, creating corrosive conditions. Test samples were exposed to air at 50 °C and 100% humidity in sealed containers; it was found that the carbon steel-weld region corroded only under radiation. Electrochemical experiments carried out at different temperatures indicate that the corrosion rate increased significantly at the lower pH caused by HNO₃ production. The presence of H₂O₂ had little effect on the corrosion rate.