Corrosion of Copper in 1 M NaCl under Strictly Anoxic Conditions
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&RUURVLRQRI&RSSHULQ01D&OXQGHU6WULFWO\$QR[LF&RQGLWLRQV Martin Bojinov, Timo Laitinen, Kari Mäkelä, Margit Snellman1 and Lars Werme2 VTT Technical Research Centre of Finland, VTT Industrial Systems, Espoo, FIN-02044 Finland 1 Saanio & Riekkola, Finland 2 SKB, Sweden $%675$&7 The corrosion of copper in 1 M NaCl has been investigated at room temperature and at 80oC by an on-line resistance probe, solution analysis of dissolved copper and weight loss measurements. At room temperature, corrosion of the copper as indicated by an increase of the probe resistance has been detected during the first 60-80 h of exposure. After the corrosion potential has reached the immunity region of Cu, a decrease in the resistance of the sensor is observed, probably due to redeposition of Cu from the solution. It can be concluded that the corrosion of copper at room temperature virtually stops after 60-80 h due to the anoxic conditions established in the experiments. The similarity in the trends of the corrosion and redox potential during exposure seems to indicate that Cu(II) contained in the native oxide on Cu and/or formed by homogeneous oxidation of Cu(I) during the initial oxic period of exposure acts as a redox-agent determining the chemical conditions in the closed system. ,1752'8&7,21 In the present Scandinavian design, spent nuclear fuel is planned to be packed in a cast iron canister with an outer copper shield for corrosion protection. The 50 mm thickness of the wall of the copper canister sets a limit of 0.5 µm y-1 for the maximum corrosion allowance of copper at a predefined lifetime of 105 years. It is possible that general corrosion of copper occurs in deep repository conditions. Thermodynamic calculations [1] indicate a possibility of copper corrosion in highly saline water environments of the anoxic type (concentration of oxygen
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