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

Abstract

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.