Depending on the heat treatment, which category of stainless steel may or may not be resistant to chloride stress corrosion cracking; generally the heat treatment that gives alloys a very high strength causes susceptibility.

• A. Martensitic
• B. Ferritic
• C. Austenitic
• D. Precipitation Hardened

Answer: (D)

Heat treatment controls the microstructure and strength of a stainless steel, which in turn governs its resistance to chloride stress corrosion cracking. In precipitation-hardening stainless steels, the very high strength comes from aging that forms fine precipitates. Those precipitates create numerous interfaces and can introduce residual stresses, making the material more vulnerable to crack initiation and propagation in chloride environments. When aged to very high strength, this susceptibility often increases, whereas in a softer, less aged state the alloy can be more resistant. So, the category whose resistance to chloride stress corrosion cracking can swing with heat treatment—often becoming susceptible at high-strength aging—is the precipitation-hardening stainless steels.