Anodizing

Anodizing is an electrochemical process that thickens a metal’s protective oxide layer by making the metal the anode in an electrolytic cell. It is used chiefly on aluminum and titanium to improve corrosion resistance, wear behavior, or appearance.

Electrolytic cell: A system that uses an external electrical source to drive a nonspontaneous chemical reaction. Anodizing makes the workpiece the positive electrode in this reaction-driving setup.
Aluminum anodizing: Anodizing applied to aluminum and its alloys to form a protective or decorative oxide coating. It is the most widely used form of anodizing.
Chromate conversion coating: A chemical treatment that forms a protective chromate-containing conversion layer on a metal surface. Unlike anodizing, it forms through chemical conversion rather than electrochemical oxide growth.
Oxidation–reduction reaction: A chemical reaction involving transfer of electrons between species. Anodizing couples metal oxidation at the surface with reduction at the counterelectrode.
Anode: The electrode at which oxidation occurs in an electrochemical cell. The metal workpiece is connected as the anode, where its surface is oxidized.
Hardcoat anodizing: A low-temperature anodizing process that produces a relatively thick, hard aluminum oxide coating. Its dense, wear-resistant layer suits components exposed to abrasion.
Powder coating: A finishing process that deposits and cures dry polymer powder on a surface. It adds a polymer film instead of thickening the metal's own oxide.
Corrosion: The deterioration of a material through chemical or electrochemical reactions with its environment. Anodizing aims to slow corrosion by creating a more protective surface layer.
Aluminum oxide: A chemical compound of aluminum and oxygen that occurs in several crystalline and amorphous forms. Anodizing aluminum builds an oxide layer whose structure depends on the process.
Titanium anodizing: Electrochemical oxidation of titanium that forms an oxide film whose optical appearance varies with thickness. It creates colored titanium surfaces without applying pigment.

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