White Coloring of Titanium by Anodic Oxidation

Abstract

White anodic oxide film was obtained by an anodic oxidation of titanium with higher voltage than the spark-ignition voltage in an electrolytic bath in which aluminum sulfate was added to the mixture solution of phosphoric acid, sulfuric acid and hydrogen peroxide.
The following is the investigated formation mechanism of electrolytic white coloring film.
When titanium is oxidized by anode in the electrolytic bath, an insulating film is formed. Then, the film is broken partially by the spark discharge to be pierced. At that time, the film is heated locally, so that aluminum is hydrolyzed at the interface between titanium and the electrolyte. In parallel with the reaction above, the film adheres to the thermal hydrolyzate. As a result, a composite anodic oxide film of titanium including aluminum oxide (hydrate) is produced.