On the Effect of the Duration of Microarc Oxidation on the Characteristics of Thermal-Control Coatings on Aluminum Alloy

The effect of the duration of the microarc-oxidation process on the thickness, roughness, and optical characteristics (solar absorbance alpha(s) and emissivity epsilon) of white and black thermal-control coatings formed on an aluminum alloy AMg6 is studied experimentally. It is found that alpha(s) decreases with an increase in the thickness of the coatings with increasing microarc-oxidation-treatment duration. For the white coatings, a decrease in their roughness is accompanied by an increase in epsilon, and vice versa. For the black coatings, the main role is played by the emissivity factor of the coating, which is determined by the content of vanadium oxide in it. A comparative analysis of the optical characteristics of thermal-control coatings obtained using the microarc-oxidation process on various aluminum alloys show that it is better to form white coatings of the solar-reflector class on aluminum alloy AMg3 and black coatings of the true-absorber class on an aluminum alloy AMg6 with a microarc-oxidation (MAO) treatment duration of 25 min. The obtained experimental data can serve as a framework for the development of a basic technology for the formation of thermal-control coatings on products made of aluminum alloys.