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 3x10-4 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. (author)