Effect of Environmental Variables on Crevice Corrosion Susceptibility of Ni-Cr-Mo Alloys for Nuclear Repositories

Abstract

The crevice corrosion repassivation potential was determined by the Potentiodynamic-Galvanostatic-Potentiodynamic (PD-GS-PD) method. Alloys 625, C-22, C-22HS and HYBRID-BC1 were used. Specimens contained 24 artificially creviced spots formed by a ceramic washer (crevice former) wrapped with a PTFE tape. Crevice corrosion tests were performed in 0.1 mol/L and 1 mol/L NaCl solutions at temperatures between 20 and 90 °C, and CaCl2 5 mol/L solution at temperatures between 20 and 117 °C. The crevice corrosion resistance of the alloys increased in the following order: 625 < C-22 < C-22HS < HYBRID-BC1. The repassivation potential (ECO) showed the following relationship with temperature (T) and chloride concentration ([Cl−]) ECO = (a + b T) log [Cl−] + c T + d; where a, b, c and d are constants. At temperatures above 90 °C, ECO for alloy 625 stabilized at a minimum value of -0.26 VSCE.