Aluminum Surface Treatment - Anodising.
Why Need Aluminum Surface Treatment?
Examples of attributes that could be achieved by surface treatment include:
What is Anodising
Anodising is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.Anodizing increases resistance to corrosion and wear, and provides better adhesion for paint primers and glues than bare metal does. It is possible to use anodising for decorative purpose as well since the surface could be dyed or with thin transparent coatings that add interference effects to reflected light.(Wikipedia)
|Layer Thickness||Application Area|
|5 µm||Protective anodising before matching, a short period of etching|
|10 µm||Normal stress indoors|
|15 µm||Indoors and outdoors in dry and clean atmospheres.|
|20 µm||Normal to hard stress outdoors e.g. construction and transport. Great stress under chemical influence indoors, e.g. in the food industry|
|25 µm||Severe stress in the form of wear or corrosive environment|
There are normally four steps in the process: pre-treatment, anodising, coloring (where required) and sealing.As you can see in the accompanying illustration, the aluminum surface forms an oxide film, which, instead of being on the surface of the metal, is incorporated into the aluminum.Aluminum oxide is a hard, durable and weather resistant substance that protects the base metal.
Merits and Demerits of Anodising:
Anodizing coatings might accumulate dirt and stains which could be removed with neutral detergent and washing technology. A thin anodic coating would be removed leaving a renewed one which could be used for another 20 years. But once the finish is damaged, the only choice is to re-coat the surface with another paint.