The influence of increased temperature from cement hydration was checked on aluminum corrosion prevention when LiNO3 was added to the cement used for aluminum waste cementation.
At first, the temperature at the center of a 0.2-m3 cement or mortar form was measured. Then, because the reaction mechanism of LiNO3 involves formation of insoluble LiH 2AlO2 5H2O (Li-Al) preservation film on an aluminum surface, the Li-Al film solubility was measured in a 0.1 M KOH aqueous solution at temperatures from 283 to 353 K. In a second experiment, an aluminum specimen was soaked in a 0.1 M KOH solution with 3 wt% of dissolved LiNO3, and the volume of generated hydrogen gas was measured. Finally, aluminum plates were solidified with mortar in a full-scale test. The mortar mixture contained ordinary portland cement (OPC), blast furnace slag (BFS), and sand with a 1.5 wt% LiNO3 addition, and the volume of generated hydrogen gas was measured.
When only OPC was used, the temperature increased to ~363 K. With the BFS and sand addition, this temperature increase was reduced by ~40 to 323 K. The Li-Al film solubility became larger as the temperature of the solution increased. The volume of hydrogen gas generation became large as the temperature increased, especially over 323 K. When the mortar consisted of OPC, BFS, sand, and LiNO3, the volume of hydrogen gas generation from aluminum was reduced, becoming <10% of that without the LiNO3 addition. Thus, it appears that the temperature did not have much influence on the ability of LiNO3 to prevent aluminum corrosion, although the ability was gradually lessened as the temperature increased.
