What are the surface treatment methods of aluminum alloy die castings?

What are the surface treatment methods of aluminum alloy die castings? According to the quick screen editor, the commonly used technologies are: Aluminum phosphating, aluminum alkaline electrolytic polishing process, aluminum and aluminum alloy environmental protection chemical polishing, aluminum and its alloy electrochemical surface strengthening treatment, and YL112 aluminum alloy surface treatment process. The details are as follows:

1. Aluminum phosphating

The accelerator, fluoride, Mn2 +, Ni2 +, Zn2 +, PO4 were studied in detail by means of SEM, XRD, potential time curve and film weight change; And Fe2 + on the phosphating process of aluminum. Research shows:

Guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation. It is an effective accelerator for aluminum phosphating; Fluoride can promote film formation, increase film weight and refine grain; Mn2 +, Ni2 +, can obviously refine the grain, make the phosphating film uniform and dense, and improve the appearance of the phosphating film; When the concentration of Zn2 + is low, the film cannot be formed or the film formation is poor. With the increase of Zn2 + concentration, the film weight increases; PO4 content has a great influence on the weight of phosphating film. Increasing PO4 content will increase the weight of phosphating film.

2. Alkaline electrolytic polishing process of aluminum

The alkaline polishing solution system was studied, and the effects of corrosion inhibitor and viscosity agent on the polishing effect were compared. The alkaline solution system with good polishing effect was successfully obtained, and the additives that can reduce the operating temperature, prolong the service life of the solution and improve the polishing effect were obtained for the first time. The experimental results show that adding proper additives to NaOH solution can produce good polishing effect.

The exploratory experiment also found that after DC constant voltage electrolytic polishing with glucose NaOH solution under certain conditions, the surface reflectance of aluminum can reach 90%, but there are still unstable factors in the experiment, which needs further research. The feasibility of using DC pulse electropolishing method to polish aluminum under alkaline condition is explored. The results show that the pulse electropolishing method can achieve the leveling effect of DC constant voltage electropolishing, but its leveling speed is slow.

3. Environmental friendly chemical polishing of aluminum and aluminum alloy

It is determined to develop a new environmental friendly chemical polishing technology with phosphoric acid sulfuric acid as the base liquid, which aims to achieve zero emission of NOx and overcome the quality defects of previous similar technologies. The key of the new technology is to add some compounds with special functions to the base solution to replace nitric acid. Therefore, it is necessary to analyze the three acid chemical polishing process of aluminum, especially the role of nitric acid. The main function of nitric acid in aluminum chemical polishing is to inhibit pitting corrosion and improve polishing brightness. Combined with the chemical polishing test in pure phosphoric acid sulfuric acid, it is considered that the special substances added in phosphoric acid sulfuric acid should be able to inhibit the pitting corrosion and slow down the overall corrosion, and must have a good leveling and brightening effect.

4. Electrochemical surface strengthening treatment of aluminum and its alloys

The process, properties, morphology, composition and structure of ceramic like amorphous composite conversion film formed by anodic oxidation deposition of aluminum and its alloys in neutral system are discussed.

The results of technological research show that in the neutral mixture system of Na2WO4, the concentration of film-forming promoter is 2.5-3.0g/l, the concentration of complex film-forming agent is 1.5-3.0g/l, the concentration of Na2WO4 is 0.5-0.8g/l, the peak current density is 6-12a / DM2, and the gray series inorganic non-metallic films with good gloss can be obtained under weak stirring. The film thickness is 5-10 μ m. The microhardness is 300-540hv and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloys, and can form films on various series of aluminum alloys such as rust proof aluminum and forged aluminum.

5. Surface treatment technology of YL112 aluminum alloy

YL112 aluminum alloy is widely used in the structural parts of automobiles and motorcycles. The material needs surface treatment before application to improve its corrosion resistance and form a surface layer that is easy to combine with the organic coating to facilitate subsequent surface treatment.