Method for forming ceramic coatings by micro-arc oxidation of reactive metals

A process for forming oxide coatings on bodies of aluminum and/or aluminum alloys, said process comprising;

• forming an electrolyte bath having a pH above 7 in an inert container;
• immersing aluminum and/or aluminum alloy bodies in said bath;
• connecting each of said bodies to a side of a single phase AC circuit;
• imposing single phase AC power potential within said bath and said bodies;
• moving said bodies in said electrolyte bath relative to each other until micro-arcs occur on the surfaces of said bodies, whereby to commence oxidation of said bodies;
• continuing the imposition of the potential within said bath until the desired thickness of oxide is formed on said bodies.

A process for forming oxide coatings on at least two bodies of aluminum and/or aluminum alloys, said process comprising;

• forming an electrolyte bath in a container;
• attaching each of the bodies to an electrode and immersing said bodies in said bath;
• connecting each of said electrodes and thus said bodies to a side of a multiphase AC circuit;
• imposing multiphase AC power potential between each of said bodies;
• moving said bodies in said electrolyte bath relative to each other until micro-arcs occur on the surfaces of said bodies, whereby to commence oxidation of said bodies;
• rotating said bodies within said bath during oxidation, whereby to oxidize said bodies with more uniform thicknesses;
• continuing the imposition of the potential between each of said bodies until the desired thickness of oxide is formed on said bodies.

An electrochemical, microplasmic oxidation process for forming tenacious, stable oxide coatings on bodies of reactive metals, reactive metal alloys, intermetallic compounds, and reactive metal-matrix composites, said process comprising:

• forming an electrolytic bath of acidic or basic compositions in a non-reactive metallic, ceramic or plastic container;
• immersing two or three metallic bodies, each connected to an electrode, in said bath;
• connecting each electrode to a three-phase AC power source;
• imposing three-phase AC power potential between each of said bodies;
• moving said bodies relative to each other in said electrolyte bath for the purpose of controlling current and current density;
• continuing the imposition of the potential between each of said bodies until the desired thickness of oxide has been formed on said bodies.