Grain Boundary Corrosion of Sulfur and Phosphorus Doped and Sensitized AISI 304 Stainless Steel

The results of a modified Strauss test on a commercial AISI 304 stainless steel, a 0.003 wt% sulfur heat, and four sulfur and four phosphorus doped heats fabricated by recasting the commercial heat are reported. The corrosion rate of each heat is measured as a function of sensitization conditions. The corrosion rate is linear with sensitization time for the doped heats when sensitized at 650 C; unrelated to sensitization time when sensitized at 550, 750, and 850 C; and independent of sensitization temperature for the low sulfur heat. The slopes of the corrosion rate vs sensitization time are dependent on the wt% of carbon, and not on the phosphorus and sulfur concentrations. A carbide precipitation model can account for the linear variation of weight loss with time.