Two corrosion resistant nickel-based alloys, 625 and C22, have been selected by the U.S. Department of Energy as candidate materials for the inner container of high-level radioactive waste packages. The susceptibility of these materials to localized corrosion was evaluated by measuring the repassivation potential as a function of solution chloride concentration and temperature using cyclic potentiodynamic polarization and lead-in-pencil potential step test methods. At intermediate Cl- concentrations, e.g., 0.028-0.4 M, the repassivation potential of alloy 625 is greater than that for alloy 825 and is dependent on the Cl- concentration. However, at higher concentrations, the repassivation potential is slightly less than that for alloy 825 and is weakly dependent on Cl- concentration. The repassivation potentials for alloy C-22 under all test conditions are considerably higher than those of either alloy 625 or 825 and are in the range where oxygen evolution is expected to occur.

Subject
Pits, Materials, Corrosion resistant alloys, Chloride ion concentration, Molybdenum alloys, Repassivation potentials, Chloride solutions, Crevices, Current densities, Crevice corrosion, Localized corrosion, Alloys, Chlorides
Keywords:
alloy 625, alloy C22, chloride, localized corrosion, crevice corrosion, nuclear waste, potential, repassivation potential, repository environments, cyclic potentiodynamic polarization
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1998
GOV
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