While surface treatments like anodic oxidation or micro-arc oxidation (MAO) significantly enhance the surface hardness and abrasion resistance of aluminum alloys, they often leave numerous dense pores or defects that compromise their corrosion resistance. Traditional sealing methods, such as boiling water or silane treatments, frequently fail to completely seal these micro-cavities and can introduce new defects due to volumetric shrinkage of the sealants, thereby reducing the service lifespan of the coatings. In this study, we introduce a novel vacuum-expansion sealing (VE sealing) strategy aimed at providing a more effective and durable sealing treatment. This method involves filling sealants in a vacuum environment, followed by volume expansion through ring-opening polymerization. Using this approach, the porosity of the porous MAO layer is significantly reduced, with the MAO-Ves coating porosity decreasing from 8.69 % to a remarkable 0.03 %. Electrochemical tests further demonstrate that after VE sealing, the sealed MAO sample maintains a higher low-frequency impedance |Z| of 1.16 × 10 Ω·cm after 672 h. This study not only presents a valuable strategy for enhancing the corrosion resistance of MAO coating, but also provides an efficient solution for improving the hardness, abrasion-resistance, and corrosion-resistance of surface-treated aluminum alloys and magnesium alloys.