| Effects of SO₄^=, Cl^- and SCN^- concentration on the corrosion behavior of sensitized AISI 316 stainless steel in various aqueous electrolytes were investigated electrochemically. Passive film breakdown potential (E_b) and induction time(IT) for pit nucleation of solutionized-sensitized AISI 316 stainless steel specimens were measured upon exposure to deaerated solution with different SO₄^=, Cl^- and SCN^- concentrations at 25℃ After the anodic polarization treatments, the morphology of corrosion pits was inspected by scanning electron microscopy. It was found that E_b gradually increased as more H₂SO₄ was added to 0.5M HCl solution and the highest E_b was obtained when 0.3M H₂SO₄ was added. Then E_b slowly decreased as SO₄^= concentration increased. In the both cases of Cl^- addition to 0.5M H₂SO₄ and SO₄^= addition to 0.5M KSCN, E_b decreased. With increasing sensitization, IT and E_b decreased in electrolytes containing Cl^-, SO₄^= and SCN^-. In addition, IT increased in the case of SO₄^= addition to 0.5M HCl solution. The morphology of pits produced by Cl^- addition showed irregular shape and smooth shape by SO₄^= addition. The SCN^- resulted in small pits and intergranular corrosion. |
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