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Sakamaki, Keiko; Kataoka, Masaharu; Maeda, Toshikatsu; Iida, Yoshihisa; Kamoshida, Michio; Yamaguchi, Tetsuji; Tanaka, Tadao
Corrosion Engineering, Science and Technology, 49(6), p.450 - 454, 2014/09
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Corrosion experiments of a carbon steel plate embedded in bentonite mixture were conducted toverify our models assessing Eh evolution induced by corrosion of carbon steel overpack. Theexperimental results showed that the Eh decreased for the first 200 days and was subsequentlystabilised at around -450 mV; corrosion products were identified as magnetite and Fe waspresent mostly as divalent Fe within a 5 mm range from the carbon steel plate. Reactive transportmodelling was performed to assess the Eh evolution in the system using kinetic dissolution modelfor metallic iron and thermodynamic equilibrium models for other chemical reactions and closelyreproduced the experimental results. The models were verified only under the conditionsemployed in this study.
Azumi, Kazuhisa*; Yajima, Jungo*; Nagai, Yuto*; Watanabe, Masatoshi; Taniguchi, Naoki; Shimizu, Akihiko*
no journal, ,
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 Cu
O. 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.
Shibata, Toshio*; Watanabe, Masatoshi; Taniguchi, Naoki; Shimizu, Akihiko*
no journal, ,
In Japan, High-level radioactive waste produced by reprocessing spent fuels has been planned to be fixed in a glass solid body which is further enclosed in metal canisters. Carbon steel is the candidate material for the canisters, because the corrosion rate of carbon steel is known to be as low as 10 microm per year at an deep underground site. Corrosion rate data of the candidate steel have been accumulated in the laboratory and fields, and the corrosion rate of steel in this environment has been found to be almost 10 microm per year at the initial stage, which decreases gradually with time. In this study, a rational corrosion model assuming the diffusion of HO molecule through the precipitated corrosion film has been developed under oxygen depleted environment. The model also assumes that the dissolution of precipitated Fe
O
film is controlled by mass transfer process through adjusting diffusion layer in the solution. Digital simulation based on the corrosion model was found well to simulate the observed corrosion rate change with time at various pHs and to predict a low and steady state corrosion rate after long time exposure.
