Definition of Anodizing

Anodizing is an electrolytic passivation process where metal is coated with a protective oxide layer to create an anode. The process is used to increase the thickness of the natural oxide layer on the surface of metal parts, increasing corrosion resistance and increasing wear resistance. Anodization changes the microscopic texture of the surface providing better adhesion for paint primers and glues. Anodic films can also be used for a number of cosmetic effects. Thick porous coatings absorb dyes and thin transparent coatings add interference effects to reflected light. Anodizing is also used to prevent galling of threaded components and to make dielectric films for electrolytic capacitors. Anodic films are most commonly applied to protect aluminum alloys, although processes also exist for titanium, zinc, magnesium and niobium.

The process is called "anodizing" because the part to be treated forms the anode electrode of an electrical circuit. Anodized aluminum surfaces, for example, are harder than aluminum but have low to moderate wear resistance that can be improved by increasing thickness or by applying suitable sealing substances. Anodic films are generally much stronger and more adherent than most types of paint and metal plating, making them less likely to crack and peel.

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