Stress Corrosion Cracking of Annealed and Sensitized Type 304 Stainless Steel in Deaerated Chloride/Sulfate Solutions at 290 C

Constant extension rate experiments at controlled potentials have been performed on both annealed and sensitized Type 304 stainless steel in deaerated chloride/sulfate solutions at 290 C. For the alloy in the annealed condition, the critical cracking potential is affected by the chloride and sulfate concentrations. Chlorides shift the critical cracking potential in the active direction while sulfates shift it in the noble direction. In the sensitized condition, the critical cracking potential is independent of the chloride or sulfate concentration. Assuming a dissolution controlled mechanism, it is suggested that chlorides reduce the rate of repassivation while sulfates increase it, thus controlling the critical cracking potential.