Influence of Deteriorated Bentonite Sediments on the Corrosion Behavior of NiCu Low Alloy Steel

The corrosion evolution of steel disposal container largely depends on the evolution of surrounding bentonite environment in the long-term geological disposal of high-level radioactive wastes. This study focused on the influence of the deteriorated bentonite sediments on the corrosion behavior of NiCu low alloy steel in the top supernatant and bottom slurry formed by Gaomiaozi bentonite and 0.05 M NaHCO₃ + 0.1 M NaCl + 0.1 M Na₂SO₄ solution. In the top supernatant, the cathodic process of the steel corrosion was transformed from the reduction in oxygen to the reduction in ferric corrosion products with time as same as that in the blank solution. While in the bottom bentonite slurry, the cathodic process always maintained as the hydrogen evolution reaction due to the coverage of more bentonite sediments. Meanwhile, the corrosion rate of NiCu steel was obviously decreased. In addition, the localized corrosion tendency of the steel could also be reduced by the large amount of deteriorated bentonite sediments.