A composite anodizing coating containing superfine Al2O3 particles on AZ31 magnesium alloy

Anodic coatings with and without superfine Al2O3 particles were prepared on AZ31 magnesium alloy by anodizing in an environmentally friendly alkaline solution. The microstructure and morphology of the coatings were analyzed using X-ray diffraction and scanning electron microscopy equipped with energy dispersive spectroscopy. The corrosion resistance of the uncoated AZ31 substrate and the anodic coatings was evaluated in 3.5% NaCl solution through potentiodynamic polarization tests. Friction and wear tests were performed to evaluate the wear resistance of the samples. The results show that the composite oxide coating has better corrosion resistance than the coating without Al2O3 nanoparticles. The microhardness of the composite coating with reinforced Al2O3 nanoparticles is up to 358 HV. When rubbed at 10 N load for 3 min during sliding against GCr15 at ambient temperature, the wear loss of the film was about 0.04 mm3, which is about one-tenth of that of the anodizing coating without nanoparticles. Therefore, the composite anodizing coating with Al2O3 nanoparticles shows better anti-corrosion and anti-wear properties than the coating without Al2O3 nanoparticles.