Zinc alloy die-casting is a precision casting method that uses high pressure to force molten metal into a complex shaped metal mold. It is a precise casting method.
There are many post-processing techniques for aluminum alloy products, mainly including the following:
1. Sandblasting is mainly used for surface cleaning. Sandblasting before painting (spray painting or plastic spraying) can increase surface roughness and contribute to the improvement of adhesion, but the contribution is limited and not as good as chemical coating pre-treatment.
2. Passivation is a method of transforming the metal surface into a state that is not easily oxidized and delaying the corrosion rate of the metal.
3. Coloring: There are two main processes for coloring aluminum: one is aluminum oxidation coloring process, and the other is aluminum electrophoresis coloring process. Various colors are formed on the oxide film to meet certain usage requirements, such as black for optical instrument parts and golden for commemorative medals.
Conductive oxidation (chromate conversion coating) - used in situations where both protection and conductivity are required.
4. Chemical polishing is a chemical processing method that utilizes the selective self dissolution of aluminum and aluminum alloys in acidic or alkaline electrolyte solutions to level and polish the surface, reducing its surface roughness and pH.
This polishing method has the advantages of simple equipment, no need for power supply, no limitation on the size of the workpiece, high polishing speed, and low processing cost. The purity of aluminum and aluminum alloys has a significant impact on the quality of chemical polishing. The higher the purity, the better the polishing quality, and vice versa.
5. Chemical oxidation: The oxide film is relatively thin, with a thickness of about 0.5-4 microns, porous, soft, and has good adsorption properties. It can be used as the bottom layer of organic coatings, but its wear resistance and corrosion resistance are not as good as anodic oxide films;
The chemical oxidation process of aluminum and aluminum alloys can be divided into two categories based on their solution properties: alkaline oxidation method and acidic oxidation method.
According to the properties of the film layer, it can be divided into oxide film, phosphate film, chromate film, and chromate phosphate film.
6. Spraying: Used for external protection and decoration of equipment, usually carried out on the basis of oxidation. Aluminum parts should undergo pre-treatment before painting to ensure a strong bond between the coating and the workpiece. There are generally three methods: phosphating (phosphate method), chroming (chromium free chroming), and chemical oxidation.
7. Electrochemical oxidation, the chemical oxidation treatment equipment for aluminum and aluminum alloys, is simple, easy to operate, has high production efficiency, does not consume electricity, has a wide range of applications, and is not limited by the size and shape of parts. The thickness of the oxide film is about 5-20 microns (the thickness of the hard anodic oxide film can reach 60-200 microns), with high hardness, good heat resistance and insulation properties, and higher corrosion resistance than chemical oxide films. It is porous and has good adsorption capacity.