Influence of different electrolyte systems on structure and property of thermal control coatings on Mg alloy

The thermal control coatings were prepared on the MB15 magnesium alloy by micro-arc oxidation in aluminates, silicates and phosphates systems. Results show that the three kinds of coating colors were black with typical micro porous structure. The phosphates coatings are thicker than the silicates coatings, while the silicates coatings are thicker than the aluminates coatings. Moreover, the roughness of phosphates coatings is similar with that of silicates coatings, and that of aluminates coatings is the minimum. Taken together, the phosphates coating has the best thermal control property. The absorptance of the thermal control coatings can be improved with the image density of coatings increasing. Meanwhile, the emissivity of coatings was enhanced by the increasing of amounts and size of the pores and bump structures on the surface. Besides, reducing the concentration of electrolyte is beneficial to the the thermal control property due to the increase of chromatic values. The thermal shock test shows that the thermostability of coatings is excellent.