Anodizing

One of the most common techniques for protecting the surface of metals, anodizing is an electrolytic process in which an oxide (anodic) layer is chemically built on the surface of the metal.

This oxide layer acts as an insulator and provides surface corrosion protection and serves as an excellent substrate for decorative finishes. In the case of anodizing aluminum the anodic oxide structure originates from the aluminum substrate itself and is composed entirely of aluminum oxide. It has a highly ordered, porous structure that allows for secondary processes such as coloring and sealing.

Anodizing is a “conversion coating” and is very different from paint, electroplating or other metal coatings. Anodize coatings are measured by thickness – the term thickness includes both penetration & build-up. While paints and plating sit on top of the surface of the aluminum, anodizing converts the outer layer of aluminum to aluminum oxide, so the coating is fully integrated with the aluminum substrate. This is the primary reason why anodize thickness is defined by the combination of the penetration into the substrate & the buildup of the oxide layer from the original dimension.