Formation and corrosion protection of layered double hydroxide film on Mg-4Li-3Al and Mg-14Li-3Al alloys

Abstract

Mg(OH)2/Mg-Al layered double hydroxide (LDH) films were prepared on the surface of single phase Mg4Li-3Al (a-Mg phase) and Mg-14Li-3Al (b-Li phase) alloys by in situ hydrothermal in pure water with chemical-free reagents, respectively. The influence of a-Mg and b-Li phases on the formation of LDH and the corresponding corrosion resistance were investigated. The differences in the growth of LDH on a-Mg and b-Li phases were discussed. Results show that Al element exists mainly as solid solution atoms in the aMg phase and mainly as intermetallic compounds in the b-Li phase, which promotes the generation of LDH. Compared with the process on the surface of a-Mg phase, the pH value of the reaction solution in b-Li phase can reach the optimal value in a shorter time for LDH growth, which can effectively reduce the hydrothermal time, and the film contains a higher content of LDH. Compared with the substrate, the corrosion current density of the films is reduced by 1-2 orders of magnitude. After hydrothermal treatment for 12 h, the LDH film on LA143 alloy has the lowest corrosion current density (2.426 3 1027 A cm2) and dense surface.