Localized Corrison of Nickel Alloys in Chloride Environments

Abstract

The localized corrosion resistance of the molybdenum bearing nickel alloys, Alloy C-276 and Alloy 625 has been studied in neutral chloride solutions in the temperature range 25 degrees - 200 degrees C, as part of the container materials evaluation screening tests for the Canadian Nuclear Fuel Waste Management Program (CNFWMP). The results of exposure tests, which are presented in the form of temperature/chloride ion (T-Cl-) corrosion diagrams, show that both alloys suffer crevice corrosion in neutral sodium chloride solutions at elevated temperatures but that, in both cases. there is a limiting temperature > 100 degrees C, below which the alloys are not attacked regardless of the chloride concentration. The actual corrosion behaviour is compared with that predicted on the basis of the electrochemical behaviour of these alloys in chloride solutions.