Laboratory study of interactions between copper and microorganisms in oxic groundwater

The interactions between copper, the canister material in the nuclear waste disposal concept in Finland and Sweden, and micro-organisms in groundwater in their expected near-field environment are the core interest of this paper. Copper specimens were incubated with ammonia-oxidising bacteria for different time periods and then subjected to electrochemical measurements and surface characterisation to provide data on biofilm formation and its effects on copper corrosion. The biofilms on the surface of copper specimens were heterogeneous, due to the morphology of corrosion products that developed during the biofilm growth phase, but they also contributed to the nature and amount of corrosion product layers on the copper surfaces. Nitrogen was systematically detected in the biofilm specimens, due to the presence of ammonia-oxidising bacteria. The electrochemical response of the specimens was so heavily linked with the detected corrosion products, often rich in chlorine from the groundwater, that the influence of ammonia-oxidising bacteria was masked. The results demonstrate that the role that biofilm formation plays in the corrosion of copper in groundwater environment is very difficult to predict even under controlled laboratory conditions.