Effect of high-entropy LDH assisted construction of composite coating with sandwich-like structure for inhibiting the galvanic corrosion of Mg-Li alloy

A novel composite coating with sandwich structure was prepared on the anodic oxidation coating (AO coating) of Mg-Li alloy, which was mainly composed of layered double hydroxide (LDH) nanosheets and electroless NiP coating. The microstructure differences between classical MgAl-LDH nanosheets and high entropy MgAlNiCrZn-LDH nanosheets (HE-LDH) and their effects on the corrosion resistance of the coatings were investigated, especially the effects of the two types of LDH nanosheets on the galvanic corrosion between Mg-Li alloy and Ni alloy coatings. The results show that the sandwich composite coating can effectively improve the corrosion resistance of Mg-Li alloy, especially to inhibit galvanic corrosion. The lifting effect of high entropy LDH sandwich composite coating is significantly higher than that of the MgAl-LDH sandwich composite coating. The coupling current density between Mg-Li alloy and Ni coating was reduced by one order of magnitude, and the self-corrosion current density of composite coating was reduced to 3.31×10 -7   A·cm -2 . HE-LDH nanosheets had better corrosion resistance, which may be due to the high charge density and densification of high-entropy LDH, which increased the adsorption and physical barrier to Cl - .