Abstract
Anodic oxide films formed on aluminum in electrolyte solutions of sulfuric, oxalic, chromic and phosphoric acid were then electrolytically colored in nickel sulfate solution and the coloring behavior was investigated. For films formed at identical voltages in different electrolytes, minimum AC coloring voltage increased with the electrolyte of formation in the order of chromic, phosphoric, sulfuric and oxalic acid solution. For films formed in the same electrolyte, the minimum coloring voltage (Vp) did not increase proportionally to increasing film formation voltage (Vf); rather, the Vp:Vf ratio decreased as Vf increased, except for films formed in oxalic acid. These electrolyte and voltage dependent behaviors on coloring are caused by differences in the nature of barrier layers and are explicable by the flaw density in the barrier layer.
The coloring behavior of sulfuric acid films was also studied in electrolyte solutions of copper, cobalt, nickel, ferrous and tin sulfate, and the minimum coloring voltage decreased in that order. The spread of AC coloring voltage broadened in the order of cobalt, tin, ferrous, nickel and copper sulfate solutions.
