Improvement of Corrosion and Wear Resistance of Mg-Li Alloy by Binary- and Ternary-Layered Double Hydroxide/Steam Coating Composite Coatings

In order to improve the corrosion resistance and frictional wear resistance of LA43M Mg-Li alloy, Mg-Al-layered double hydroxide (LDH)/steam coating (SC) and Mg-Al-Co LDH/SC composite coatings were prepared on an LA43M Mg-Li alloy substrate by in situ steam coating and subsequent hydrothermal treatment. X-ray diffraction, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to analyze the microscopic morphology, composition, and phase of the coatings. The corrosion resistance and wear properties of the coatings were characterized by immersion, hydrogen evolution, and friction and wear experiments. The LDH/SC composite coatings formed on the surface of the Mg-Li alloy after hydrothermal treatment all contained nanostructures and predominant lamellar structures and had high crystallinity. The corrosion resistance was in the following order: Mg-Al-LDH/SC > Mg-Al-Co LDH/SC > SC > LA43M. Friction and wear experiments showed that the average coefficients of friction of LA43M and the SC were higher and fluctuated more widely and the abrasion marks were deeper and wider in comparison with the LDH/SC composite coatings. Both LDH/SC composite coatings exhibited improved corrosion resistance with respect to the SC, which protected the alloy. The Mg-Al-LDH/SC composite coating exhibited better corrosion resistance than the Mg-Al-Co LDH/SC composite coating.