Anodizing is the process of creating an aluminum oxide coating by making an aluminum part anodic while suspended in an electrolyte. The electrolyte most commonly used is 15% by weight sulfuric acid; however chromic acid is sometimes used for aircraft parts. The process takes anywhere from thirty minutes to one hour, and the thickness ranges from .3 mils to 2 mils. The aluminum oxide coating that is produced is porous by nature and has the ability to adsorb dye or exhibit an excellent anchor profile for paint. Also it can be sealed if these properties are non desirable. Below are some of the most common specifications for anodizing.

Type I (Chromic Acid Anodize) Type II (Conventional Anodize) Type III (Hardcoat Anodize)

Above: Conventional anodized parts dyed.