Effects of Composition on the Stress Corrosion Cracking of Ferritic Stainless Steels^⋆

U-bend and axially loaded tensile-type specimens were used in stress corrosion tests performed in boiling 140 C (284 F) magnesium chloride solution. The experimental ferritic alloys tested contained 17 to 25% chromium, 0 to 4% nickel, 0 to 2% copper, and 0 to 5% molybdenum. Alloys essentially free of nickel and copper did not undergo stress corrosion cracking. (Tests on Types 430 and 434 stainless steels confirmed this behavior.) However, alloys containing more than 1% nickel or 0.5% copper were subject to transgranular stress corrosion cracking in boiling magnesium chloride solution. Critical concentrations of copper and nickel that produce susceptibility to cracking were determined at various chromium and molybdenum levels. Experiments at controlled potentials indicated that cracking in boiling magnesium chloride was not the result of hydrogen embrittlement.