May 14, 2011

Anodizing on Titanium

This is actually the metal that actually seldom to use because it very expensive metal to use in general application. Anodizing on titanium may apply as follow to the anodizing definition itself that Anodizing define as electrolytic passivation, the process that affect on the metal to increase the thickness of the natural oxide layer on the surface of metal parts.

The surface of titanium metal will covered by oxide of titanium, this similar as happen on aluminum anodizing. After anodized on the titanium metal then can be coloring by heating. The most common method is to form an oxide layer by electrolytic means, similar to the process of electroplating. The work to be colored is attached to the positive connection of power supply (anode), and usually another piece of titanium is connected to the negative side (cathode) of the supply. Both of this electrode than submerge in a middle conductive solution, such as phosporic acid, TSP (Tri Sodium Phosphate).

When the power is applied to the contacts, a uniform layer of titanium oxide forms on the anode. As the voltage increases, the thickness of the layer also increases. Certain color will appear at specific voltage levels, the change from one color to another is not sharply defined, but rather shades gradually through a limited spectrum.

The basic setup for anodizing titanium as follows:

  • A container - large enough to hold the work to be anodized 
  • An electrolytic solution Acid phosphoric, TSP or TSP PF cleaning solution, etc)
  • A variable power supply - ideally this should be able adjusted from 0 - 150 Volt DC and can sustain 10 - 15 Ampere of current.
  • A cathode - usually a strip of scrap titanium
  • An anode -  this is the titanium piece to be anodized