Comparative Corrosion Behavior of Copper Alloys in Oxygen-Present and Oxygen Reduced Groundwater for Korean Deep Geological Repositories

Abstract The corrosion behavior of oxygen-free copper and phosphorus deoxidized copper was investigated in oxygen-present and oxygen reduced groundwater of Korean deep geological repository environments. Electrochemical testing including impedance spectroscopy, potentiodynamic polarization, and immersion tests were conducted, complemented by surface analysis techniques. Results revealed that both materials exhibited significantly higher corrosion resistance in oxygen-reduced environments, with corrosion rates below 0.02 µm/year compared to up to 0.37 µm/year in oxygen-present conditions. Equivalent circuit modeling demonstrated that oxygen-reduced conditions promoted diffusion-controlled processes resulting in thin oxide layers, while oxygen-present conditions led to thicker corrosion products. Oxygen-free copper consistently outperformed phosphorous deoxidized copper in both environments, showing lower corrosion current density values (0.001 mA/cm² vs 0.002 mA/cm² in oxygen-reduced conditions) and higher charge transfer resistance. This enhanced performance is attributed to the lower oxygen content of Oxygen-free copper, achieved through electrolytic refining. These findings provide valuable insights for the selection of canister materials optimized for Korean radioactive waste repository environments.