GMW GMW14665 PDF

This specification covers basic requirements for anodic coatings on aluminum and aluminum alloys.

Material Description. The anodic coating is an oxide film produced by an electrolytic oxidation process, during which the aluminum acts as the anode. The oxide film causes an improved corrosion protection. Anodic coatings must be either sealed or painted to maintain their appearance. Anodic coatings are suitable for decorative and/or functional applications. Normally the anodic film is transparent, but depending on the application, the film can also be colored before sealing either with a dye or with a combined electrolytic coloring process involving metal ions. The maximum thickness is typically 15 μm.

A special type of anodic coating is hard anodize. Those are characterized by their hardness and a thickness of more than 25 μm. Hard anodized coatings are used sealed, as well as unsealed. For applications that need a high corrosion protection, and also a high wear protection, the hard anodic film may not be sealed. For applications that need a very high corrosion protection, but only a low wear protection, the hard anodic film has to be sealed. Aluminum and aluminum alloy substrates coated to this specification may be pretreated suitable to the base material and surface conditions, to obtain the required coating and surface properties.

Symbols. Not applicable.

Typical Applications. Anodic films are used for:

Decorative parts for internal and external applications. External applications should be limited to above beltline. Applications below beltline are subject to a special release and specific requirements of a higher level must be defined. The corrosion load in that area is much higher than above beltline (e.g., because of additional loading from copper containing brake dust).

Functional parts for internal and external applications.

Hard anodized films are used only for functional parts for external applications.