White Anodic Coatings on Aluminum Alloy with Low Ratio of Solar Absorptance to Infrared Emittance

Abstract

White anodic coatings are gained by growth in situ on the aluminum alloy. The coatings possess stable optical properties, excellent adhesive power, low cost, stability in the space environment, and so on, which can be widely used in the thermal control system of spacecrafts. In this article, the developed Al2O3 thermal control coatings that had a low solar absorptance and a high infrared emittance were gained in the electrolyte of sulfuric acid. The influences of various process parameters, such as electrolyte temperature, current density, anodizing time, on the optical properties of the coatings were investigated. AFM and XRD were used to characterize the microstructure of the coatings. Experimental results show the anodic coatings could reach a solar absorptance value lower than 0.20 and an infrared emittance higher than 0.80. Therefore, the coatings can be applied as important thermal control coatings for space applications.