In order to develop a new surface treatment technology for aluminum-lithium alloys, an AA2099-T83 alloy was anodized in a tartaric-sulfuric acid bath and then post-treated in lithium carbonate (Li₂CO₃) solutions of different temperature-concentration combinations. The results show that the post-treatment in Li₂CO₃ solutions can greatly improve corrosion resistance of the anodized alloy (withstanding up to 1300 h of neutral salt spray test). It is found that the sealing process is distinctly different for high-temperature/low-concentration and low-temperature/high- concentration combinations. Specifically, the anodic film is only partially sealed in high-temperature mode but more fully sealed in low-temperature mode. The mechanism for the high corrosion resistance of the treated alloy is ascribed to the barrier effect of the sealing products (i.e., Li-Al-LDH and/or boehmite) on the surface and in the interiors of the anodic film.