Electrolytic coloring of anodic aluminum for selective solar absorbing films: use of additives promoting color depth and rate

An optically black coating on aluminum substrate having improved solar absorption is disclosed along with an enhanced process for formation. The two-step electrolytic coloring process has been used. Porous anodic films have been formed by dc anodization of aluminum samples in 16% sulfuric acid. It i...

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Bibliographic Details
Published in:Renewable energy 2001-07, Vol.23 (3), p.489-495
Main Authors: Shaffei, M.F, Abd El-Rehim, S.S, Shaaban, N.A, Huisen, H.S
Format: Article
Language:English
Subjects:
Applied sciences
Energy
Equipments, installations and applications
Exact sciences and technology
Natural energy
Solar energy
Solar thermal conversion
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Summary:An optically black coating on aluminum substrate having improved solar absorption is disclosed along with an enhanced process for formation. The two-step electrolytic coloring process has been used. Porous anodic films have been formed by dc anodization of aluminum samples in 16% sulfuric acid. It is followed by black coloration via ac electrolysis in nickel sulfate solution. In this step, we have investigated the effect of chloride and magnesium as additives. Evaluation of the test samples has been carried out by spectral reflectance and nickel content measurements. Choride existance verifies two aspects: the promotion of the coloring process and higher black tones shades are attained. However, magnesium has a minor effect.
ISSN:0960-1481
1879-0682
DOI:10.1016/S0960-1481(00)00129-4