Investigating the Effect of Nitric Acid on Corrosion of Copper Coating Materials Containing Various Amounts of Oxygen

Abstract

For the past decade the Nuclear Waste Management Organization (NWMO) of Canada has been evaluating the feasibility of using copper-coated containers emplaced bentonite to contain used nuclear fuel within a Deep Geological Repository (DGR). The location of the DGR will be selected by 2024, with an informed and willing host community, after which technical work will increasingly focus on site-specific performance. For container corrosion programs, this will mean an enhanced analysis of the performance of copper within the local geology and expected water chemistry.

Unlike copper overpacks, copper coatings have few mechanical requirements, as structural support is provided by underlying steel. This has led to a desire to create a purity specification for copper coatings that emphasizes both corrosion performance and trace chemical species that may be incorporated into the coating during the manufacturing process. The most recent results from the coating purity program show that amongst different non-metallic impurities, trace oxygen does affect the reactivity of copper in aggressive conditions (i.e., anodic polarization, nitric acid exposure, high sulfide concentrations). Although early oxidizing DGR conditions are nowhere near as aggressive as those in this experimental program and are very short-lived, with respect to the DGR lifetime, the results are insightful with respect to understanding the copper reactivity.

This paper presents select findings from copper purity project focusing on the effect of nitric acid on cold sprayed copper coating materials containing various amounts of oxygen.