COLORING METHOD FOR ALUMINUM OR ALUMINUM ALLOY

PURPOSE:To increase the coloring speed and to perform a coloring finish in a short time by electrolyzing anodically oxidized Al or Al alloy in an electrolytic soln. contg. Ni salt after adding hypophosphorous acid or its salt to the soln. CONSTITUTION:Hypophosphorous acid or its salt is added to an aqueous soln. contg. Ni sulfate, Ni sulfamate or other Ni salt to prepare an electrolytic soln. Anodically oxidized Al or Al alloy is immersed in the electrolytic soln. and electrolytically colored at a prescribed temp. and voltage for a prescribed time using an Ni plate or the like as an opposite electrode. Thus, black of a fine color tone and bronze in an intermediate step are obtd.