Five surface treatment methods for aluminum alloy die castings

1. Aluminum phosphating
The effects of accelerators, fluoride, Mn2+, Ni2+, Zn2+, PO4; and Fe2+ on the phosphating process of aluminum were studied in detail by using SEM, XRD, potential-time curve, film weight change and other methods. 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 grains; Mn2+, Ni2+, can significantly refine The crystal grain makes the phosphating film uniform and compact and can improve the appearance of the phosphating film; when the Zn2+ concentration is low, the film cannot be formed or the film formation is poor. As the Zn2+ concentration increases, the film weight increases; the PO4 content affects the weight of the phosphate film Larger, increasing the content of PO4 will increase the weight of the phosphating film.
2. Alkaline electrolytic polishing process of aluminum
Conducted research on alkaline polishing solution system, compared the effects of corrosion inhibitors, viscosity agents, etc. on the polishing effect, and successfully obtained an alkaline solution system with good polishing effects, and for the first time obtained the ability to reduce the operating temperature and prolong the use of the solution. It is an additive that can improve the longevity and polishing effect at the same time. The experimental results show that adding appropriate additives to the NaOH solution can produce a good polishing effect.
Exploratory experiments also found that after DC constant voltage electrolytic polishing with glucose NaOH solution under certain conditions, the reflectivity of the aluminum surface can reach 90%, but due to the unstable factors in the experiment, further research is needed. The feasibility of using DC pulse electrolytic polishing method to polish aluminum under alkaline conditions is explored. The results show that the pulse electrolytic polishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but its leveling speed is slow.
3. Aluminum and aluminum alloy environmentally friendly chemical polishing
It is determined to develop a new environmentally friendly chemical polishing technology based on phosphoric acid-sulfuric acid. This technology must achieve zero emission of NOx and overcome the quality defects of similar technologies in the past. The key to the new technology is to add some compounds with special effects to the base fluid to replace nitric acid. For this reason, it is first necessary to analyze the three-acid chemical polishing process of aluminum, especially focusing on 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 believed that the special substances added in phosphoric acid-sulfuric acid should be able to inhibit pitting corrosion and slow down overall corrosion, and must have a better leveling and brightening effect.
4. Electrochemical surface strengthening treatment of aluminum and its alloys
The process, performance, morphology, composition and structure of the ceramic-like amorphous composite conversion coating formed by anodic oxidation and deposition of aluminum and its alloys in a neutral system were preliminarily discussed.
Process research results show that in the Na2WO4 neutral mixing system, the concentration of film-forming accelerator is controlled to be 2.5-3.0g/l, the concentration of complexing film agent is 1.5-3.0g/l, and the concentration of Na2WO4 is 0.5-0.8g/l , The peak current density is 6-12A/dm2, and weak agitation can obtain a complete, uniform, and good-gloss gray series inorganic non-metallic film. The film has a thickness of 5-10μm, a microhardness of 300-540HV, and excellent corrosion resistance. The neutral system has good adaptability to aluminum alloys, and can form a good film on various series of aluminum alloys such as rust-proof aluminum and forged aluminum.
5. YL112 aluminum alloy surface treatment technology
YL112 aluminum alloy is widely used in structural parts of automobiles and motorcycles. The material needs to be surface treated before application to improve its corrosion resistance and form a surface layer that is easily combined with the organic coating to facilitate subsequent surface treatment.
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