SURFACE TREATMENT FOR TITANIUM OR TITANIUM ALLOY AND TITANIUM MATERIAL OR TITANIUM ALLOY MATERIAL

摘要

PURPOSE:To form a dark-brown or black film by forming a colored film by using a solution of borofluoric acid or a solution of acidic potassium fluoride respectively in specific concentration ranges. CONSTITUTION:A borofluoric acid solution of 0.5-50wt.% concentration or a potassium fluoride solution of 0.05-10wt.% concentration is held at about 20-40 deg.C, and titanium or titanium alloy is immersed in this solution for about 2-3min, taken out, washed with water, and dried, by which a dark-brown or black film is formed on the metal surface according to immersion time. When the concentration of the borofluoric acid is =0.5%, the film does not take on color, and, when =15%, the velocity of a reaction dissolving an oxide film becomes higher than the velocity of oxide film formation and, as a result, a black film cannot be formed. The same applies to the concentration range of the acidic potassium fluoride. By this method, the dark-brown or black film can be stably formed in a short time in easy operations without using particular devices.