Types of Anodizing...

There are many different types of anodizing. Sulfuric acid anodizing is most common as it produces a porous oxide layer.  There are other processes where other electrolytes are used such as chromic acid, phosphoric acid and sulfuric-boric acid.  Using these different electrolytes produces oxide layers with different properties than those produced with sulfuric acid.  In addition, process conditions such as temperatures can be changed to produce very hard oxide coatings.

There are three different types of Anodizing:

  • Type I anodize refers to chromic acid anodizing.
  • Type II anodize is nominal "clear" sulfuric acid anodizing.
  • Type III is "hardcoat" using sulfuric acid or mixed chemistry electrolytes.

All types are describe in detail in the anodizing standard, MIL-A-8625.