Chloride Stress Corrosion Cracking (Cl-SCC) in Stainless Steel
Chloride SCC is the leading cause of catastrophic, unexpected failure in austenitic stainless steel piping.
Critical Conditions for Chloride SCC
Three conditions must coexist: (1) tensile stress; (2) chloride ions; (3) temperature above ~60°C for 304, or ~80°C for 316L. Remove any one, and SCC cannot initiate.
Why 304 and 316 Are Vulnerable
Austenitic stainless steels are inherently susceptible to transgranular chloride SCC. The mechanism involves chloride ions disrupting the passive Cr₂O₃ film. The crack tip is anodic relative to the surrounding passive surface — the crack propagates while the rest of the pipe looks perfectly intact.
Materials Resistant to Chloride SCC
Duplex 2205
Immune up to 150°C
Super Duplex 2507
Immune up to 250°C
Alloy 825 / 625
Fully immune
Alloy 400
Fully immune