Abstract: A process and apparatus for forming oxide coatings on bodies of aluminum and aluminum alloys are described. The process includes forming an electrolyte bath in an inert container. At least two reactive metal bodies are suspended in the bath. The bodies are connected to electrodes which, in turn, are connected to a multiphase AC circuit. A multiphase power (preferably three-phase between three bodies) potential is imposed between each of the bodies. The bodies are moved in the electrolyte bath relative to each other until micro-arcs occur on the surfaces of the bodies, whereby to commence oxidation of the bodies. The imposition of the potential between each of the bodies is continued until the desired thickness of oxide is formed on the bodies.