Inhibition Effect of NaNO2 on 16MnR Steel in Bentonite

In order to ensure the integrity of the waste container over an extended period and prevent the proliferation of radionuclide in the container, anti-corrosion coating was painted on the surface of the container and bentonite land fill was compacted for the disposal of high level waste (HLW). Stress produced in expansion and contraction process of bentonite would destroy the anticorrosion coating of waste container. Cl- contained in the backfill material and groundwater can invade the steel/bentonite interface, resulting in damaying the passivation and localized corrosion of the steel. Immersion corrosion experiment of 16MnR steel was carried out in mixed solution of groundwater and cole alkali bentonite. The inhibition effect of NaNO2 on 16MnR steel in bentonite was studied. In addition, considering that unsaturated permeability of compacted bentonite is significant to the evaluation of backfill and buffer material properties, pressure plate extractors were used to measure the soil-water characteristic curves of the original bentonite and NaNO2 added bentonite. The experimental results showed that the inhibition efficiency was proportional to the concentration of NaNO2 when the concentration of added NaNO2 was greater than the critical concentration. The inhibition efficiency was up to 95% when the concentration increased to 0.60%. Water-absorption/holding rate of NaNO2 added bentonite was slower than that of the original bentonite, and the water holding capacity of NaNO2 added bentonite was relatively good.