Optical properties of spectrally selective anodically coated electrolytically colored aluminum surfaces

Abstract

Optical properties of solar absorbing surface coatings made by electrolytic coloration of anodically oxidized aluminum have been investigated. It was found that the surfaces colored with Ni, Sn and Cu were spectrally selective absorbers and that their optical properties were a function of oxide thickness and concentration of coloration metal. The values of α s obtained were in the range of 0.90–0.95 and ϵ was in the range of 0.1–0.3. The surfaces colored with Ni were stable up to 400°C under infrared (oven) heating conditions as well as under concentrated solar irradiation. Surfaces colored with Sn and Cu were less stable. AES and SEM measurements were used to generate a microstructural model for the coating.