Abstract: A process for electrolytically coloring an aluminum material wherein a base aluminum or aluminum alloy is anodized and the anodized material is electrolyzed in a second electrolytic coloring step using a bath containing nickel and zinc salts, a chelating reagent for nickel ions and a supporting electrolyte at a pH of 4.5 or greater using alternating, direct or dual alternating-direct current electrolytic processes. A molybdate may also be employed in the secondary electrolysis process and the resultant coating has a color ranging from a grey series to black.

Abstract: In the process of electrocoloring aluminum by passage of alternating current between anodized aluminum and a counter-electrode while immersed in a bath containing a salt of one or more of the group nickel, cobalt, tin, the range of colors obtainable by the process is extended by subjecting aluminum, which has been anodized under conventional D.C. conditions while immersed in a sulfuric acid-based electrolyte, to an electrolytic treatment in a phosphoric acid based electrolyte before the electrocoloring operation.