Anodizing
If you are looking for a tough, protective coating but also want a unique finish, anodizing may be what you are searching for. Anodizing is an electro-chemical process that converts the surface of raw aluminum to an artificial oxide coating. Anodizing is not a plating process because, unlike plating, anodizing doesn't deposit any material onto the metal surface. It is acutally a complex series of steps involving pre-cleaning, etching, deoxidizing, anodizing, dying and sealing with careful rinsing after each immersion. Most types of aluminum can be anodized, the purer grades producing a better finish.

The process involves placing aluminum in an electrolyte, sulfuric acid and passing a low-voltage current through it. The aluminum part is connected to the positive anode and the negative anode is connected to a lead cathode, which causes the aluminum to oxide, siminlar to the process of steel rusting. This results in the formation of a very hard, tough and protective coating. The most exciting feature of anodizing is the amazing array of colors and effects that can be produced. Following immersion in an organic dye, parts are sealed with a nickel acetate seal, which literally closes the pores of the anodized coating, preventing the dye from leaching and the anodic film from deteriorating.