Corrosion Behavior of Carbon Steel in Alkaline and Reducing Simulated Groundwater

Abstract

This study was conducted in order to clarify the corrosion behavior of a carbon steel disposal container for low-level radioactive waste. The corrosion morphologies to be considered and the occurrence conditions of localized corrosion with the carbon steel as a candidate material were evaluated in aqueous solutions that simulate groundwater equilibrated with cement. As a result of the electrochemical evaluation for the possibility of occurrence of localized corrosion, the re-passivation potential for crevice corrosion was consistently more noble than the corrosion potential in DO<3×10⁻⁴ mass ppm, pH 11.5∼13.5. As a result, it was considered possible to make allowance for the localized corrosion in the solution environment despite Cl⁻ content. Furthermore, when Cl⁻ content was low concentration near 0 mass ppm, the occurrence of localized corrosion could be neglected despite DO and pH. On the other hand, the measurement of hydrogen generation equivalent corrosion rate on the assumption that general corrosion was dominant revealed that the corrosion rate was in 0.067∼0.1μm/y at pH 12.3. Assuming that the burial period of a carbon steel container would be about 10 million years, it was concluded that the corrosion wastage would be approximately 10 mm.