STRESS-CORROSION CRACKING OF LOW STRENGTH, LOW-ALLOY NICKEL STEELS IN SULFIDE ENVIRONMENTS

Factors governing stress corrosion cracking (SCC) of low strength, low alloy nickel steels in sulfide environments were investigated using a three point loaded bent beam specimen. Cracking occurred in both weld and base metal at low H//2S partial pressures (to 0. 001 atmosphere) and stress levels, but could be inhibited by a neutralizing amine (morpholine) and methanol addition as used for control of ice and hydrate formation in cryogenic gas plants. Cathodic polarization experiments showed cracking was retarted under these conditions. Sulfide corrosion stress cracking (SCSC) is suggested as a term for this type of localized anodic cracking attack in sulfide environments.