Anodizing

Anodizing also spelled anodising, is a process for producing decorative and protective films on articles made of aluminum and its alloys. Before anodising the surface of the article must be thoroughly cleaned, normally using a detergent-based process, and etched with a solution of sodium hydroxide.

After anodizing the surface may be colored with a dye or by an electrolytic method using appropriate metal cations and then sealed by placing in boiling water, the pores in the oxide layer being closed off.

Anodizing increases resistance to corrosion and wear, and provides better adhesion for paint primers and glues than bare metal does. Anodic films can also be used for some cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light.