Regenerative lubricant-impregnated oxide layers for enhanced durability of aluminum alloys

Surface treatment of aluminum and its alloys is necessary to compensate for insufficient wear and corrosion resistance. Sufficient improvements in corrosion and wear resistance simultaneously have rarely been reported. Recently, lubricant-impregnated nanoporous oxide layers have been introduced to utilize surface functionalities and improve the corrosion resistance of aluminum alloys. Silicone oil was used to create a lubricant-impregnated nanoporous anodic aluminum oxide to simultaneously improve wear and corrosion resistance. The oxide surface coated with a hydrophobic self-assembled monolayer of polydimethylsiloxane (PDMS) and the silicone oil impregnated within porous structure effectively reduced the mechanical friction by 13 % compared to bare anodic oxide. Moreover, the PDMS damaged by wear can be continuously restored on the oxide surface by the frictional heat generated during wear as long as the porous oxide surface is wetted by silicone oil. Therefore, compared to conventional lubricants (e.g., perfluorinated, engine, or vacuum oils), which cannot form a monolayer on oxides, the silicone oil-impregnated nanoporous oxide of aluminum shows a significantly low friction coefficient (μ = ∼0.1) and high wear resistance. Moreover, due to the monolayer of PDMS and its regeneration on the damaged area, the silicone oil-impregnated surface not only has significantly high corrosion resistance, but also stable anti-corrosion against physical damage showing >99 % lower corrosion current density on wear region than conventional lubricants-impregnated surfaces.