Crevice corrosion resistance of super-austenitic and super-duplex stainless steels in chloride solutions

Abstract

Abstract The crevice corrosion resistance of super-duplex S32750, and super-austenitic S31254 and S32654 stainless steels was assessed in chloride solutions, at different temperatures. Alloys S32750 and S31254 suffered crevice corrosion between 30 and 90°C, while alloy S32654 only suffered crevice corrosion at 60 and 90°C. The crevice corrosion repassivation potential of alloys S31254 and S32654 decreased with increasing temperatures and chloride concentrations. The repassivation potential of alloy S32750 did not show a clear dependence neither with temperature nor with chloride concentration in the tested conditions. Crevice corrosion initiation of the alloys was significantly affected by temperature while repassivation was less affected by temperature. Varying the chloride concentration from 10,000 to 100,000 ppm did not produce a significant effect on the crevice corrosion kinetics in the tested conditions. At 30°C, alloy S32654 clearly outperformed alloys S32750 and S31254. However, at 60 and 90°C the three tested alloys showed comparable crevice corrosion resistances. The crevice corrosion current density of the tested alloys showed a maximum value in a potential range below the secondary passivity. This may be due to an inhibiting effect of the oxyanions released at these high potentials.