Traditionally there are three major ways of surface treatment for aluminum profiles, powder coating, anodization and fluorocarbonation.
Powder coating is widely used in constructional aluminum profiles and other cast aluminum parts. It covers the base metal, the aluminum alloy, with a layer of resin powder. It provides adequate protection to the base metal with coating thickness of 40-100μm. In normal climates, or even in coastal regions, it will easily last 5-15 years without any obvious change. Also, there are lots of choices for the color. In recent years, there is a new kind of coating powder coming into popularity, with the appearance very close to fluorocarbon. Therefore, powder coating can be deemed as the most adaptable surface treatment.
Wood finish, to some extent, is a derivation from powder coating. It is a kind of processing where wood pattern is transferred onto the powder coated surface (something like xeroxing), making the aluminum profiles look like real wood. A new treatment called ‘3D wood finish’ even allows the aluminum profiles to 'feel' like real wood.
Anodization is a process similar to plating, artificially oxidizing the aluminum in a pool filled with chemical. The coating thickness is normally 8-12μm for constructional use. If the profiles are used in coastal areas, it is suggested the coating be increased to 15-20μm to enhance the protection from salty air. In extreme cases, particularly in industrial use, a 'hard anodization' will be applied. Such anodization can be as thick as 100μm and it can even resist the scratch by a knife. Anodization, to a large extent, maintains the natural pattern and gloss of aluminum alloy. However, there are only limited choices of color for constructional use. The most usual colors are silver (natural color), bronze/champaign and black. Though there are other colors available, such as red, green, gold and so on, but they are rather sensitive to climates, particularly to sunshine. These colors are normally not used on the aluminum profiles for outdoor construction. On the other hand, anodization is also very sensitive to the composition of aluminum alloy. If the purity of aluminum is not high enough or other elements are too much, the anodized surface will look drab and uneven. For example, cast aluminum normally cannot be anodized as the composition of silicon is too high.
Blasting (or sanding) and polishing can be regarded as the derivatives from anodization. They involve the chemical or physical processing on the surface of aluminum profiles before anodization, making them appear matt or shining.
Fluorocarbonation is a process very close to powder coating but the equipment and formula are totally different. It can be coating by 1-ply to 3 ply while powder coating can only be done by 1-ply. This treatment can even resist the erosion of strong acid and alkali, which cannot be achieved by powder coating or anodization. The price of such treatment is often twice or even quadruple of normal powder coating and anodization. It is normally used on very high-end construction.