Anodized

Anodized refers to a family of electrochemical processes that thickens and modifies the natural oxide layer on a metal surface, most commonly aluminum. The resulting oxide film is integral to the surface, improves durability, and can be decorative through coloration. Anodized finishes are prized for increased hardness, wear resistance, and enhanced corrosion resistance in many environments.

In an anodizing bath, the workpiece is made the anode in an electrolytic cell and an oxide layer grows from the metal into the electrolyte as electrical current passes. Aluminum forms a porous aluminum oxide layer, whose pore size and overall thickness depend on the electrolyte type, voltage, and time. Common electrolytes include sulfuric acid, oxalic acid, and phosphoric acid. After formation, the porous layer can be sealed to reduce porosity and improve corrosion resistance, and may be dyed or left clear for a natural finish. Thickness typically ranges from a few micrometers to several tens of micrometers, with thicker coatings used for higher wear resistance.

Materials and finishes: Aluminum is by far the primary material for anodizing, though some magnesium, titanium, and zinc alloys can also be anodized with suitable processes. The resulting surface is more resistant to chemical attack and can accept a wide range of colors through dyeing, or retain a natural, transparent appearance when sealed appropriately. The oxide layer is hard but can be damaged by aggressive abrasion if not protected.

Applications: Anodized finishes are common on aluminum cookware, architectural profiles, automotive and electronics components, and consumer products, where a durable, decorative, and corrosion-resistant surface is desirable.