ステンレス鋼のすきま腐食再不動態化電位に及ぼす表面処理の影響

抄録

Repassivation potentials, E_R, were measured in 0.5mol/l NaCl solution at 30°C for PTFE/metal-crevice of surface treated stainless steels which had been dipped for 6h in 61% nitric acid containing 40g/l Na₂Cr₂O₇·2H₂O at 50°C. Under usual measuring conditions, or in case of ordinary extent of previous growth of crevice corrosion, the E_R values obtained were constant and coincided with critical crevice corrosion potential, V_crev, above which crevice corrosion could initiate and continue to grow. These facts confirm that the concept of E_R as a well defined characteristic can be applied also to surface treated stainless steels. As the second stage of the study effects of variables in surface treatment procedures on E_R values were determined. Most noble values of E_R were obtained for steels which had been dipped for 6h in 61% HNO₃+(20-40)g/l Na₂Cr₂O₇·2H₂O solutions at 50°C. Such optimum conditions as evaluated through E_R measurements would be effective to improve crevice corrosion resistance for the steels.