Electrolytic White Coloring of Anodic Oxide Film on Aluminum in Mixed Al3+-Ca2+ Electrolytic Bath

概要

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Anodic oxide film on aluminum is subjected to secondary electrolysis in an electrolytic bath containing Al3+ and/or Ca2+ to allow aluminum and calcium oxides (hydrates) to be deposited in fine pores in the film, thus serving for white coloring of the film. Three electrolytic baths are examined. One contains an aqueous calcium sulfate solution alone and a second one contains additional ammonium aluminum sulfate 12-water (ammonium alum). The third is prepared by adding gluconic acid to the latter mixture solution. As test samples of anodic oxide film, double layered film is prepared by performing anodic oxidation successfully in a sulfuric acid bath and then in a phosphoric acid solution bath. The results show that film most homogeneously colored with the highest whiteness degree is obtained when A. C. electrolytic coloring is carried out in a bath containing calcium sulfate and ammonium alum. Aluminum and small amount of calcium (both appearing to be a hydrate) are found to be deposited in the resultant film. A. C. voltage scanning reveals that the deposition of these substances occurs rapidly arouud 18 V.
Japan Society of Colour Materialの論文