Investigation of Corrosion-Resistant MAO@ZnO/LDH/HDTMS Composite Coating on Mg-Li Alloy Surface

Due to the poor corrosion resistance of Mg-Li alloys and the limited effectiveness of single surface treatment methods, developing a composite coating is essential to significantly enhance the corrosion protection. In this study, a stable ceramic coating was fabricated on the surface of a Mg-Li alloy by micro-arc oxidation with regulation of the concentration of ZnO nanoparticles added to the electrolyte. Layered double hydroxides (LDH) was subsequently prepared on the coating surface by modulating the hydrothermal temperature, contributing to blocking the micropores and cracks to enhance the compactness of the coating. Additionally, a low-surface-energy hexadecyltrimethoxysilane (HDTMS) was selected to self-assemble on a rough micro/nano structured MAO/LDH coating to obtain a superhydrophobic surface The composite coating exhibited exceptional corrosion resistance, with the R ct value increasing by four orders of magnitude compared to the substrate and the Y 0 (CPE out ) reduced to the 10 -9 range. Furthermore, the coating keeps almost non-corrosion morphology after 7 days of immersion in 3.5% NaCl solution, which is attributed to the combined effects of the superhydrophobicity of HDTMS, the physical barrier effect and chloride ion trapping ability of LDHs, and the reduction in porosity achieved through the incorporation of nano-ZnO in MAO coating.