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Anodizing is a process for building up a corrosion-resistant or decorative oxide layer on the surface of a metal (usually aluminum or magnesium) objects. The item to be anodized is made the anode in a cell containing an aqueous solution of sulfuric, chromic, or oxalic acid as electrolyte. The desired oxide coating is formed when a current is passed through the cell (see electrolysis). Further treatment can render this oxide layer waterproof, electrically insulating, or brightly colored.

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