Stress Corrosion Cracking of Stainless Alloys in Alkaline Sulfide Solutions

The resistance of commercial austenitic, ferritic, and duplex alloys to stress corrosion cracking in a 5% NaOH–2% Na2S–2% Na2CO3–0.2% Na2SO4–0.1% NaCl solution at 150°C has been studied by immersion tests and electrochemical measurements. The effects of alloy composition, solution composition, and test temperature on the occurrence of stress corrosion cracking were examined. It was found that either high chromium or high nickel contents were necessary to increase stress corrosion cracking resistance and that the presence of sodium chloride, sodium carbonate, and sodium sulfate had little effect on stress corrosion cracking resistance. Cracking of U-bend stressed specimens was found to occur at a potential near the active/passive transition range of SUS304L (UNS S30403). The results are discussed with reference to electrochemical behavior and the analyses of surface corrosion films.