Effect of LiNO3 on Corrosion Prevention of Aluminum Wastes after Their Land Disposal

After their land disposal, LiNO₃ added to cement solidified miscellaneous wastes inhibits hydrogen gas generation due to alkaline corrosion of aluminum contained in the wastes. We considered the presence of an Li-Al preservation film prevents hydrogen gas generation, and then, we assumed a scenario in which the amount of LiNO₃ included in the waste packages is lowered by underground water penetration, resulting in dissolution of the Li-Al preservation film. This dissolution allows the alkaline underground water to reach and corrode the aluminum materials. The loss of Na₂O and K₂O in cement by underground water penetration lowers the pH, so that the aluminum corrosion in the waste packages with LiNO₃, expected when the Li-Al preservation film dissolves, is less than that without LiNO₃.

To test this scenario, we measured solubility of the Li-Al preservation film, Li⁺ ion concentration, pH variation by underground water penetration, and aluminum corrosion when the Li-Al preservation film had dissolved. The measured solubility of the Li-Al preservation film was 3 × 10^?4 _M at 283 K. At that time, pH was lowered from 12.9—13.0 to 12.2—12.3. As a result, with LiNO₃ addition the aluminum corrosion amount was reduced to 10% of that without LiNO₃ addition, because of the pH decrease.