Evolution of Cu2O Morphology During Copper Corrosion in the Presence of Gamma-Radiation

In this work, experiments were carried out in order to develop a mechanistic understanding of the corrosion of copper metal in limited water volumes under gamma-radiation. When exposed to gamma-radiation, water decomposes into chemically reactive oxidizing and reducing species. Under a continuous radiation flux, the concentrations of the radiolytically produced oxidants eventually reach a pseudo-steady state that can influence the corrosion kinetics of metallic surfaces. The evolution of the surface morphology during water droplet corrosion of copper in the presence of gamma-radiation was investigated as a function of irradiation time and pH. The oxide growth kinetics were studied by measuring the amount of dissolved copper in the test solution after irradiation, and analyzing the oxide composition and morphology on the metal surface as a function of time. The predominant corrosion product was copper (I) oxide (Cu2O). The detailed analysis carried out here of Cu2O formation and growth has allowed a mechanism for radiolytic copper corrosion to be proposed. The mechanism consists of three stages: 1. initial oxidation of Cu0(m) to Cu2+(aq), 2. Cu2O crystal growth via reduction, and 3. redox-cycle-assisted ripening of Cu2O crystals. Each stage consists of elementary steps whose reaction rates can impact the kinetics of particle growth and influence the final morphologies of the particles observed on the metal surface. The results and derived mechanism show that the morphology of the oxide formed on the metal surface affects the corrosion rate of the metal. This work could offer critical insights into to the corrosion behaviour of copper-coated spent nuclear fuel containers exposed to gamma-radiation in a deep geologic repository. The non-uniformity of the evolution of surface morphology observed in different regions on the copper surface indicate that the corrosion of copper could be highly variable under deep geologic repository conditions