In-situ corrosion monitoring of Cu foil immersed in bentonite-contact solutions

Azumi, Kazuhisa*; Yajima, Jungo*; Nagai, Yuto*; Watanabe, Masatoshi; Taniguchi, Naoki ; Shimizu, Akihiko*

Copper have been considered for one of the candidates for container material for vitrified radioactive waste and has been thought to be corroded in the deep underground at the initial stage of underground depository. The underground water contains various ions including small amount of silica. In this study, corrosion rates of Cu foil immersed in various solutions with and without dissolved silica were monitored by using temperature-compensated resistometry and the foil surfaces were observed by using FE-SEM. It was found to suppress the corrosion of Cu foil with very small amount of dissolved silica in comparison to without silica. From Raman spectra of Cu samples, main corrosion product of these samples without dissolved silica solution was speculated to be CuO. However, the sample corroded in the solution with dissolved silica showed strong Raman peak, which seems to be indicate that the flat deposits were a kind of silicate with electric insulator property. Such silicate deposits might be swelled in the aqueous solution and were expected to suppress dissolution process of Cu ions.