Chloride-induced crevice corrosion of alloys 625, C-22, C-22HS and HYBRID-BC1 was studied at different temperatures. Crevice corrosion occurred tens of degrees below the reported critical crevice temperatures obtained through standard immersion tests. Concentrated calcium and sodium chloride solutions showed the same aggressiveness regarding crevice corrosion behavior of alloys C-22 and HYBRID-BC1. The crevice corrosion repassivation potential decreased as the temperature and chloride concentration increased. For alloys 625 and C-22, the repassivation potential reached a minimum limiting value which was coincident with the corrosion potential in the crevice-like solution. For alloys C-22HS and HYBRID-BC1, these conditions are expected to be reached above the tested temperatures. The high dependence of the repassivation potential on chloride concentration was attributed to the ohmic potential drop caused by passivating species at the alloy/solution interface. A temperature dependence of 4-9 mV/K was observed for the repassivation potential in dilute chloride solutions while it decreased to 2-3 mV/K in concentrated chloride solutions. In the context of the localized acidification model, the corrosion potential in the crevice-like solution did not depend on the temperature while the anodic polarization to maintain the crevice acidity and the ohmic potential drop decreased linearly as temperature increased.

The crevice corrosion repassivation potential of austenitic UNS S30400 and UNS S31600 stainless steels was determined in 0.1 mol/L and 1 mol/L NaCl solutions and in 5 mol/L CaCl 2 solution at temperatures between 0°C and 90°C. The repassivation potential of UNS S30400 decreased with increasing chloride concentrations and temperatures in the range from 0°C to 60°C, reaching a constant value of −0.430±0.015 V SCE in the range from 60°C to 90°C. The repassivation potential of UNS S31600 showed a continuous decrease with increasing chloride concentrations and temperatures. Crevice-corroded spots showed crystalline attack plus pitting corrosion. Crystalline attack prevailed in UNS S31600 and pitting corrosion prevailed in UNS S30400. A solution of 0.5 mol/L HCl was used to simulate the crevice-like environment. Results of repassivation potential were analyzed in the context of Galvele's localized acidification model. The ohmic potential drop was the dominant contribution in determining the repassivation potential for both steels. The contribution of the polarization to sustain the critical crevice was nil. The main effect of the 2.5 wt% Mo addition in UNS S31600 compared to UNS S30400 on the crevice corrosion resistance was the increase of the ohmic potential drop within the corroded area. This effect was especially significant for the more dilute chloride solutions and for increasing temperatures.

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