Preparation of cobalt aluminate-containing coatings by pulsed anodic oxidation under spark discharge

Abstract

A blue-colored coating containing CoAl₂O₄ crystals was successfully prepared through the anodic oxidation of aluminum with pulsed wave under spark discharge in an electrolytic bath with 10 g/L Co(OH)₂. Cobalt aluminate, CoAl₂O₄, was formed by the chemical reaction of Al₂O₃ and Co(OH)₂ on the Al surface during the anodic oxidation process. The properties of the crystalline species, film thickness, surface roughness and color of the films can be controlled by regulating the spark discharge energy through the variation of the frequency of the applied current density with a square wave during the anodic oxidation under spark discharge.