Comparative Study on Corrosion Resistance of Binary and Ternary Layered Double Hydroxide Films on Magnesium Lithium Alloy

Layered double hydroxide (LDH) (Mg-Al and Mg-Al-Co) films were prepared on the surface of LA103Z magnesium-lithium alloy by hydrothermal synthesis method. Corrosion resistance of binary and ternary LDH coatings was studied by comparison. Structures of the two films were characterized using XRD, FTIR, SEM and EDS, and the corrosion resistance of the films was evaluated by polarization curve, EIS, and hydrogen evolution rate during immersion in 3.5 wt% NaCl solution. Results showed that Mg-Al LDH film was tightly bonded to the substrate and had a large number of nanosheets growing perpendicular to the substrate, while Mg-Al-Co LDH film was thinner with a smaller size and fewer nanosheets. Electrochemical test results showed that the polarization resistance of Mg-Al and Mg-Al-Co LDH films was two orders of magnitude higher than that of the substrate. Hydrogen precipitation experiments showed that corrosion resistance of both the films was improved compared to the substrate, and the films played a protective role for the substrate, among which the corrosion resistance of the Mg-Al LDH layer was better than that of the Mg-Al-Co LDH layer. GRAPHICAL ABSTRACT