Improving corrosion and wear resistances of 2195 Al-Li alloy by PEO and LDHs composite coating

In this study, a composite coating comprising a ceramic film and layered double hydroxide (LDHs) layer was prepared on the surface of extruded 2195 Al-Li alloy. The preparation method, surface morphology, and chemical composition of the coating were described and characterized in detail. The corrosion and wear protection of the coating on the Al-Li alloy substrate were tested, and the mechanisms of corrosion and wear resistance were discussed. The results indicate that plasma electrolytic oxidation processing can form a thick ceramic film with good interface bonding on the surface of 2195 Al-Li alloy. Hydrothermal reaction in an alkaline solution produces a nanoscale layer of Mg/Al LDHs on the surface of the ceramic film. The LDHs layer fills the micro-pores and cracks in the film and effectively prevents the corrosion medium from permeating and damaging the alloy matrix. The composite coating reduces the surface corrosion efficiency by 99.98 %. Moreover, the composite-coated samples exhibit long-lasting corrosion resistance in seawater and exfoliation corrosion environments. Additionally, the composite-coated Al-Li alloy exhibits wear resistance 1-2 orders of magnitude higher than that of the bare alloy at both room and high temperatures. This study proposes a novel strategy for corrosion and wear protection of Al-Li alloys.