ã€China Aluminum Industry Network】 1. Chemical oxidation method generates a thin oxide film on the surface of aluminum parts at a certain temperature, known as the chemical oxidation of aluminum. This method does not require current flow, and is simpler and less costly than electrochemical oxidation. The resulting oxide film is very thin. Generally, the film thickness is about 0.5 to 4 μm. The film is soft and has low abrasion resistance. Therefore, it cannot be used alone. The film has good physical adsorption ability and is a good bottom layer for painting. After oxidation, the resulting protective layer can greatly increase the protection of the parts. Measuring Tape,Metric Tape Measure,Rolling Tape Measure,Metric Tape SHANGQIU CHAOYUE MEASURING TOOLS CO., LTD , https://www.equipmentool.com
2. Anodizing Anodizing of aluminum alloys uses aluminum or aluminum alloys as anodes, and uses lead, carbon, or stainless steel as cathodes for electrolysis in aqueous solutions such as oxalic acid, sulfuric acid, and chromic acid. Anodic oxidation by electric power can provide a film formation rate that is difficult to obtain by the natural oxidation method.
In the oxide film formation process, two processes occur simultaneously: one is the process of forming an Al2O3 oxide film on the surface of the aluminum plate, and the other is that the oxide film formation process is accompanied by the dissolution process of the oxide film. Only when the oxide film formation rate exceeds the dissolution rate, can get a certain thickness of the oxide film, the film thickness is generally 5 ~ 15μm. The film is a two-layer structure composed of a dense barrier layer and a porous layer of a columnar structure.
Anodized films can be divided into two major categories: porous type - films formed in acid electrolytic baths such as sulfuric acid, oxalic acid, etc. and forming very fine pores perpendicular to the surface; barrier type - in neutral salt electrolysis such as ammonium borate The non-porous extremely thin film produced in the bath is generally used for electrolytic capacitors and the like.
3. Microarc Oxidation Microarc oxidation, also known as plasma oxidation, is a surface treatment technique for growing ceramic layers on the surface of metal substrates in situ on the basis of anodizing. Its basic performance is similar to ceramic (corundum), with high hardness and wear resistance, high temperature performance, but also has a high degree of insulation and acid and alkali corrosion resistance.
4. Rare-earth conversion films have made great progress in this field at home and abroad. The rare-earth passivation technology developed has attracted much attention due to its characteristics of non-toxic, non-polluting, and good anti-corrosion effect. At present, the rare earth conversion film process can be roughly divided into three categories:
1 Chemical methods containing film-forming accelerants such as strong oxidants;
2 Chemical and electrochemical processes;
3 rare earth bohmite layer process. The addition of strong oxidants such as H2O2, KMnO4, (NH4)2S2O4, etc. can greatly reduce the processing time, the solution treatment temperature is not high, and chemical processes with strong oxidizing agents that form a film at a low temperature for a short time are more potential for development; The combination of electrochemical processing steps is cumbersome, and the solution processing temperature is also boiling; the rare earth bohmite layer process also has the disadvantage of higher processing temperature.
5. Silanization treatment of organic silanization Traditionally, dip coating is used. The aluminum alloy is immersed in this dilute silanization solution for a certain period of time, and then cured at a certain temperature to form several hundred nanometers thick on the aluminum alloy surface. The coating (which is much thinner than conventional conversion coatings) is effective in preventing various forms of corrosion of aluminum alloys.
Hu Jiming et al. used electrochemical techniques to deposit dodecyltrimethoxysilane (DTMS) films on the surface of LY12 aluminum alloys. Reflective absorption infrared spectroscopy shows that the DTMS silane reagent has a chemical bonding interaction with the surface of the aluminum alloy substrate, forming a -SiOAl bond to achieve film formation, electrochemical impedance spectroscopy (EIS) test results show that, compared with the open circuit potential, using the cathode potential deposition method The corrosion resistance of the silane film was significantly improved.
6, Phosphating primer treatment Phosphating primer base, the first component of polyvinyl butyral resin, plus chromate and other anti-rust pigments and additives, component two for phosphoric acid, before use The two components are mixed in a prescribed proportion and evenly sprayed on the surface of the aluminum plate, a part of the phosphoric acid is combined with the metal aluminum, so that the metal surface and the coating film are integrated, the coating film has a certain anti-corrosion ability, and can be used with the bottom of the coating system. The paint has good binding ability. However, the phosphating primer requires high construction conditions. If it is not careful, it will cause the paint film to become brittle and cause serious consequences of large scale paint loss.