Which temperature range is commonly associated with susceptibility to CUI in austenitic stainless steel piping under chloride exposure?

Which temperature range is commonly associated with susceptibility to CUI in austenitic stainless steel piping under chloride exposure?

• A. 0°F to 50°F
• B. 50°F to 100°F
• C. Between 120°F and 400°F
• D. Above 400°F

Answer: (C)

CUI risk for austenitic stainless steel under chloride exposure is highest when moisture can persist on the surface and diffusion of chloride ions into the protective oxide layer is favorable. Austenitic stainless steels rely on a chromium oxide passive film for corrosion resistance, but chlorides can penetrate that film and initiate pitting and crevice corrosion. This tendency is most pronounced in a mid-range temperature window where condensate remains on the insulated surface and chloride ions remain mobile, roughly between 120°F and 400°F. Below about 120°F, moisture may be present but diffusion and corrosion rates are lower, and above about 400°F, water tends to evaporate and the under-insulation environment changes, reducing the CUI risk in this context. Therefore, 120°F to 400°F is the appropriate range where susceptibility to CUI with chloride exposure is most significant.

CUI risk for austenitic stainless steel under chloride exposure is highest when moisture can persist on the surface and diffusion of chloride ions into the protective oxide layer is favorable. Austenitic stainless steels rely on a chromium oxide passive film for corrosion resistance, but chlorides can penetrate that film and initiate pitting and crevice corrosion. This tendency is most pronounced in a mid-range temperature window where condensate remains on the insulated surface and chloride ions remain mobile, roughly between 120°F and 400°F. Below about 120°F, moisture may be present but diffusion and corrosion rates are lower, and above about 400°F, water tends to evaporate and the under-insulation environment changes, reducing the CUI risk in this context. Therefore, 120°F to 400°F is the appropriate range where susceptibility to CUI with chloride exposure is most significant.