Epoxy-based polymer was deposited as sealing agent on porous anodized coatings prepared by plasma electrolytic oxidation (PEO) to construct multilayered "soft-hard" coatings on Mg substrates. Different thicknesses and microstructures of the top epoxy layer were achieved by employing different dip-coating strategies. Atomic force microscopy, pull-off tests, and nanoindentation tests were conducted to study the surface roughness, the adhesion strength of the epoxy layer, and the mechanical properties of each component in the hybrid coating system. The micropores and other defects on the anodized layers were sealed by the epoxy polymer, which decreased the surface roughness. The dominant abrasive wear behavior of blank PEO coatings was significantly reduced by the epoxy layers, and the wear mechanism of the hybrid coatings was proposed considering both the microstructure of the hybrid coatings and the mechanical properties of the different components in the hybrid system.
Keywords: PEO; epoxy polymer; hybrid coating; magnesium; wear properties.