Aluminum alloys are widely used in various industries due to their lightweight and excellent mechanical properties. To further enhance their performance and aesthetics, several surface treatment methods are applied. Here, we will discuss some of the most effective surface treatments for aluminum alloys, including conductive oxidation, aluminum coloring, sandblasting, chemical oxidation, electrochemical oxidation, and spraying.
1.Conductive Oxidation (Chromate Conversion Film)
Conductive oxidation, also known as chromate conversion coating, is used for both protective and conductive applications. This method provides a corrosion-resistant layer while maintaining the electrical conductivity of the aluminum surface, making it ideal for electronic components.
2.Aluminum Coloring
Aluminum coloring is generally achieved through two processes: oxidation coloring and aluminum electrophoresis coloring. In oxidation coloring, various colors are formed on the oxide film, meeting diverse aesthetic requirements. Electrophoresis coloring involves the deposition of colored particles on the surface, offering a wide range of color options.
3.Sandblasting
Sandblasting is a surface cleaning process where abrasive particles are blasted onto the aluminum surface. This method removes impurities and enhances surface roughness, improving the adhesion of subsequent coatings. Although it offers limited improvement, it is often used as a pretreatment step before spraying or plastic coating.
4.Chemical Oxidation
Chemical oxidation creates a thin oxide film, typically 0.5-4 μm thick, which is porous and soft with excellent adsorption properties. This film serves as a good base layer for organic coatings. However, its wear resistance and corrosion resistance are inferior to those of an anodic oxide film. Depending on the solution properties, chemical oxidation processes for aluminum and its alloys are divided into alkaline and acid oxidation processes. Based on film properties, it can be categorized into oxide film, phosphate film, chromate film, and chromate phosphate film.
5.Electrochemical Oxidation
Electrochemical oxidation, or anodizing, is a highly efficient method that does not consume power and can be applied to aluminum parts of any size and shape. The resulting oxide film is thicker, about 5-20 microns, with hard anodic oxide films reaching up to 60-200 microns. This film has high hardness, excellent heat resistance, insulation properties, and superior corrosion resistance compared to chemical oxide films.
6.Spraying
Spraying is used for the external protection and decoration of aluminum equipment. It usually follows an oxidation treatment to ensure strong adhesion between the coating and the aluminum surface. The main pretreatment methods include phosphating (phosphate), chromating (no-chromium), and chemical oxidation.
By utilizing these surface treatment methods, the durability, corrosion resistance, and aesthetic appeal of aluminum alloys can be significantly enhanced, making them suitable for a wide range of applications.
