Anodizing is the process of creating a controlled oxide coating on  
aluminum. A number of types of anodize processes have been 
developed for various end uses, the more popular types are:

Chromic Acid Anodizing Improves corrosion protection  Paint base for aircraft and marine parts Mil-A-8625, Type I Sulfuric Acid Anodizing Cosmetic, most specified of the types Ability to be dyed to a wide range of colors Mil-A-8625, Type II  Sulfuric/Oxalic Acid Extremely hard, dense coating (Hardcoat) High wear resistance   Mil-A-8625, Type III Other types include Boric Acid, Oxalic Acid, Phosphoric Acid, and  
   anodizing solutions for architectural products.