Electrolytic Coloring of Anodic Aluminium for Selective Solar Absorbing Films

摘要

An optically black coating with improved solar absorbance is generated. The process of formation pertains to the two-step electrolytic coloring of anodic aluminum. It involves the modification of the anodic barrier layer. The procedure encounters minor additives to the electrolytic coloring bath. The present investigation has shown that:1. Solar absorbance increases with increasing nickel content of the oxide layer.2. Solar absorbance in the case of using additives is improved, and values in excess of 0.96 can be attained.3. The mechanism of chloride in modifying the barrier layer approaches that of localized pitting corrosion.4. Solar absorbance decreases about 10 percent with sealing.5 Substantial reduction in the coloration time needed to reach a particular black color at normal temperature has been verified.