Display omitted •Plasma electrolytic oxidation and hydrothermal treatment are applied to Mg alloy.•Oil-impregnation and hydrophobizing enhances de-wetting of porous oxide layer.•Oil-impregnated hydrophobized nanoporous surface has superior corrosion resistance.•The surface shows durable corrosion resistance and de-wetting property. Magnesium alloys have been widely employed for structural parts of aircrafts and automobiles to reduce their weight. However, magnesium alloys are easily corroded, thus practical applications always require protective coatings to guarantee satisfactory lifetime. In this study, we applied oil-impregnation and hydrophobizing to traditional plasma electrolytic oxidation (PEO) of magnesium alloy. Nanoporous hydroxide surface structure is fabricated by hydrothermal treatment of PEO-treated Mg alloy, then the self-assembled monolayer of perfluorodecyltrichlorosilane (FDTS) is coated for the hydrophobizing. The immiscible oil impregnation into the PEO-treated oxide layer with hydrothermal treatment and hydrophobizing significantly enhances the corrosion resistance as well as the mobility of water droplet on the surface. In addition, since the oil layer on the nanoporous surface inhibit the direct contact and penetration of corrosive liquid to the oxide layer, the oil-impregnated surface shows less degradation in corrosive liquid with long-term immersion than hydrophobic and superhydrophobic surface without oil-impregnation. These results indicates that oil-impregnated surface of Mg alloy has durable and robust anti-corrosion property.