aluminum mill finish

Here are 6 different types of finishes for extruded aluminum:

#1 Mechanical Finishes

Aluminum can be buffed, blasted, polished, grinded or sanded. These finishes can improve surface quality or prepare the aluminum for other cosmetic finishes.

#2 Pretreatment

The aluminum is either etched or cleaned with alkaline or acidic materials. Then a pretreatment coating is applied. This coating enhances powder or paint adhesion and provides resistance against corrosion.

#3 Bright Dipping

An extrusion can be bright dipped, giving the aluminum a specular or “mirror” finish. To do this, technicians put the profile into a special dip solution (a combination of hot phosphoric and nitric acids). After bright dipping, profiles can also be anodized, thickening the metal’s corrosion-resistant oxide layer.

#4 Anodizing

This electrochemical process provides additional protection aside from the natural oxide film. A durable, porous anodic oxide layer is formed on the surface of the aluminum. Anodized aluminum will also accept vibrant colors. You can anodize any kind of aluminum alloy.

#5 Liquid Paint

These coatings come in many colors and provide a uniform film thickness. Liquid coatings generally contain volatile organic compounds (VOCs). They are driven off during the curing or baking process. When the VOCs are gone the volume solids form a film on the extrusion.

#6 Powder Coating

Powder coatings leave behind a film that can meet stringent performance criteria. At the same time, they do not contain VOCs. This is ideal for meeting environmental regulations on VOCs. The product is applied as a solid on the extrusion. While going through the oven process, solid particles fuse together to form the film.

#7 Sublimation

Have you ever seen aluminum extrusions that look like wood? After applying a base coat of powder, profiles can go through sublimation. Technicians wrap the profiles in a thin film with a pattern on it. The sublimation process transfers that pattern directly onto the extrusions.