Thermal control coatings on magnesium alloys prepared by plasma electrolytic oxidation

Four kinds of oxide coatings with different solar absorptance properties were prepared on AZ91D magnesium alloys by plasma electrolytic oxidation. They were of different colors due to the different additives in the electrolytes. The microstructure and composition were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The optical properties were investigated by the UV-VIS-NIR spectrophotometer, and the thermal control properties were measured by solar spectrum reflectometer as well as emissivity tester. Results showed that the solar absorptance of the coatings ranged from 0.439 to 0.918 while the emittance remained unchanged.