The surface treatment of aluminum materials is as follows:
1. Sandblasting is mainly used for surface cleaning. Sandblasting can increase the surface roughness before painting (spraying or plastic spraying), which has a certain contribution to the improvement of adhesion, but its contribution is limited. It is inferior to chemical coating pretreatment.
2. Passivation is a method to change metal surface into a state that is not easy to be oxidized and to slow down the corrosion rate of metal.
3. Coloring: There are two main coloring processes for aluminum: one is aluminum oxidation coloring process, the other is aluminum electrophoresis coloring process. Various colors are formed on the oxide film to meet certain requirements, such as black used in optical instrument parts, golden yellow on commemorative stamps, etc.
Conductive oxidation (chromate conversion coating) - used for both protective and conductive occasions.
4. Chemical polishing is a kind of chemical polishing method, which uses aluminum and aluminum alloy as selective self-dissolving agent in acidic or alkaline electrolyte solution to leveling and polishing the annealing surface in order to reduce its surface roughness and PH.
This polishing method has the advantages of simple equipment, no power supply, no restriction on the size of the parts, high casting speed and low processing cost. The purity of aluminum and aluminum alloy has a great influence 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 thin, thickness is about 0.5-4 micron, and porous, soft, with good adsorption, can be used as the bottom layer of organic coatings, but its wear resistance and corrosion resistance are not as good as anodic oxidation film;
Chemical oxidation processes of aluminum and aluminum alloys can be divided into alkaline oxidation and acid oxidation according to their solution properties.
According to the nature of film, it can be divided into oxide film, phosphate film, chromate film, chromate phosphate membrane.
6. Spray: used for external protection and decoration of equipment, usually on the basis of oxidation. Aluminum parts should be pre-treated before painting to make the coating and the workpiece bond firmly, there are three general methods: phosphating (phosphate method), chromizing (chromium-free), chemical oxidation.
7. Electrochemical oxidation, aluminum and aluminum alloy chemical oxidation treatment equipment is simple, easy to operate, high production efficiency, does not consume electrical energy, a wide range of applications, not limited by the size and shape of parts. The thickness of the oxide film is about 5-20 microns (the thickness of hard anodic oxide film can reach 60-200 microns). It has higher hardness, good heat resistance and insulation, higher corrosion resistance than chemical oxidation film, porous, and good adsorption capacity.