Influence of ZnO on thermal control property and corrosion resistance of plasma electrolytic oxidation coatings on Mg alloy

Thermal control and corrosion resistant coatings have been fabricated by means of plasma electrolytic oxidation on AZ91 Mg alloy in the present study. The coatings were achieved mainly by in-situ incorporation of nano-sized ZnO particles into the porous layer and optimization of the composition of the base electrolyte. It was found that addition of ZnO nanoparticles influences the absorptance and emissivity of the coatings. The absorptance of the coating is greatly decreased by the inertly incorporated ZnO nanoparticles. This is probably due to the high band gap energy of ZnO, which can reduce the coating absorptance accordingly. The coating emissivity has been increased in the presence of particles since ZnO has high infrared emissivity value. Moreover, the corrosion resistance of PEO coatings has been improved in the presence of ZnO particles, owing to the accumulation of ZnO in the open pores and decrease of the coating porosity. •The inertly incorporated ZnO particles decrease the absorptance of the coatings.•Coating emissivity is increased in the presence of ZnO particles.•Addition of ZnO decreases the porosity and enhances corrosion resistance of the layer.