Pit Transition Potential and Repassivation Potential of Stainless Steel in Thiosulfate Solution

The transition potential and the repassivation potential of AISI type 316 stainless steel was investigated in the absence and the presence of 0.01 M thiosulfate in chloride containing media. The pencil electrode method was employed to explore the key factors affecting the pit transition potential and the repassivation potential in thiosulfate containing solution. Using this method the pit chemistry at various temperatures was also evaluated. A good correlation was found between the pitting potential and the pit transition potential at various temperatures. Moreover, there was a significant decrease in the repassivation potential by addition of 0.01 M thiosulfate. The results were in accordance with the theory suggesting that the chemistry of the pit governs the pit repassivation potential.