Four surface treatment methods of aluminum alloy die castings

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. The results show that 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 compact, and improve the appearance of the phosphating film; When Zn2 + concentration 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, and PO4 can be increased. The content increases 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 appropriate additives to NaOH solution can produce good polishing effect. The exploratory experiment also found that after DC constant voltage electrolytic polishing with NaOH solution of glucose under some conditions, the surface reflectivity of aluminum die casting can reach 90%, but there are still unstable factors in the experiment, which need to be further studied. The feasibility of polishing aluminum under alkaline conditions by DC pulse electropolishing method is explored. The results show that the leveling effect of DC constant voltage electropolishing can be achieved by pulse electropolishing method, 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 monosulfuric acid as the base solution. This technology should realize 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 effects to the base solution to replace nitric acid. Therefore, it is necessary to analyze the three acid chemical polishing process of aluminum cnc machining parts, especially the effect 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 pitting corrosion and slow down overall corrosion, and must have good leveling and brightening effect

4. Electrochemical treatment of aluminum alloy and its surface strengthening

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 film-forming process and mechanism are discussed. The process research results show that in Na_ 2WO_ 4 in the neutral mixed system, the concentration of film-forming accelerator is controlled to be 2.5 ~ 3.0g/l, and the concentration of complex synthetic film agent is 1.5 ~ 3.0g/l, Na_ 2WO_ 4 the concentration is 0.5 ~ 0.8g/l, the peak current density is 6 ~ 12a / DM ~ 2, and the gray series inorganic non-metallic films with integrity, uniformity and good gloss can be obtained by weak stirring. The thickness of the film is 5 ~ 10 μ m. The microhardness is 300 ~ 540hv and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloy, and film can be formed on various series of aluminum alloys such as antirust aluminum and metal 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 organic coating for subsequent surface treatment.

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