Corrosive Behavior of Copper Canisters under Air and Aerobic Groundwater at Early Stages of Deep Geological Disposal

Copper oxidation at low temperatures below 140 °C and its effects on corrosive behavior in aerobic groundwater are investigated to estimate the intactness of canisters at early stages of disposal. The Cu coupon surface is covered by fine particles that form thin oxide layers after 30 d of oxidation; a thin Cu2O layer of thickness < 100 nm is formed after oxidation at 40 °C; after oxidation at 140 °C, the Cu2O surface changes to a CuO layer of thickness < 500 nm. The thickness of the Cu surface oxidized at 90 °C is between those of the surfaces oxidized at 40 and 140 °C. All Cu coupons exhibit similar current densities ranging from 0.77 to 1.87 μA cm−2, although the corrosion potential of the Cu coupon layered with Cu2O is higher than that of the others. Long-term oxidation tests for 406 d reveal no significant changes in the Cu surface at temperatures below 90 °C, indicating no significant change in the electrochemical behavior. The results of this study suggest that the storage of canisters at temperatures below 90 °C has no significant effect on the degradation of canister performance in long-term disposal.