Anodic polarization behavior of pure copper in carbonate solutions and in bentonite/sand mixture

Kawasaki, Manabu*; Taniguchi, Naoki ; Kawakami, Susumu

Copper is one of the candidate materials for overpacks. Anodic polarization curves of pure copper were measured at 80C in carbonate solution and in bentonite/sand mixture in order to understand the corrosion behavior of copper overpack at oxidizing period. The experimental results in carbonate solutions indicated that the anodic polarization curves became active dissolution type with increase in chloride ion concentration, while anodic polarization curves became passive type with increase in bicarbonate ion concentration. No effect of sulfate ion concentration was observed on the type of anodic polarization curve. The passive film break down potential became less noble with increase in chloride ion concentration and sulfate ion concentration. In contrast, the passive film break down potential became noble with increase in bicarbonate ion concentration. By the comparison of these experimental results with previous study performed at 30 C, it was indicated that anodic polarization curves become passive type with the rise of temperature. However, no effect of temperature on passive film break down potential was observed within the experimental conditions. As to the results in bentonite/sand mixture, the effect of the composition in test solutions on the anodic polarization curves were small and the anodic polarization curves were almost active dissolution types.