Q. I want to find how would you remove the bluish color from the surface of titanium products? A.U.
A. The blue color that is formed on a titanium alloy is an oxide coating. Titanium oxide is extremely stable and difficult to remove when formed. It cannot be removed by typical heat treatment (i.e., like a bright annealing of a stainless steel to remove heat tint and other oxidation products). Although I have not tried it, one chemical recipe I have seen for cleaning titanium is a mixture of nitric acid at about 40% by volume and hydrofluoric acid at about 2-3% by volume. That should have some amount of sacrificial titanium already dissolved in it and used warm (about 120-140°F).
The above mixture is dangerous and would have to be used with adequate safety protection and protective equipment (consult individual material safety data sheets), very good ventilation and when complete, would require disposal according to local and state laws. If there are readers, especially in aerospace that have more experience in deoxidation of titanium, feel free to forward your information to me. I could feature it in a future column.