Surface stability and electrochemical behavior of additively manufactured copper in repository-relevant environments

The long-term stability of disposal canisters is determined by their corrosion resistance in deep geological disposal environments. This study investigates the surface stability, electrochemical behavior, and mechanical properties of wire arc additively manufactured (WAAM) Cu and Cu alloys compared with forged oxygen-free copper (OFC) in repository-relevant groundwater. Electrochemical experiments and surface characterization under aerobic and anaerobic groundwater conditions were correlated with nanoindentation results. Under aerobic conditions, all materials exhibited comparable corrosion behavior with predominantly uniform corrosion. In contrast, under anaerobic conditions, AM-Cu showed higher corrosion current densities than OFC, associated with heterogeneous surface reactions. Under sulfide-containing environment, the corrosion current density of OFC was approximately 3.5 times lower than AM-Cu, despite the formation of more continuous Cu 2 S corrosion products on AM-Cu. Polarization behavior showed a gradual increase in current density in anodic region for AM-Cu, suggesting less stable surface corrosion-product evolution than that of OFC. Nanoindentation results showed that AM-Cu possesses higher hardness and elastic modulus than OFC, suggesting a trade-off between mechanical strengthening and electrochemical stability. These findings demonstrate that process-induced heterogeneity in AM-Cu affects surface corrosion-product formation and electrochemical behavior under repository-relevant environments.