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Four Surface Treatment Methods For Aluminum Die-Cast Parts

December 21, 2021

Cylinder head casing


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1. Aluminum phosphating

Through the use of SEM, XRD, potential time curve, film weight changes, and other methods, a detailed study of the promoter, fluoride, Mn2+, Ni2+, Zn2+, PO4, and Fe2+ and other effects on the phosphating process of aluminum.

Guanidine nitrate has good water solubility, low dosage, rapid film formation, is an effective promoter of aluminum phosphating: fluoride can promote film formation, increase film weight, refining grain; Mn2+, Ni2+ can significantly refine the grain, so that the phosphate film uniform, dense and can improve the appearance of phosphate film; Zn2+ concentration is low, can not form a film or poor film, with Zn2+ concentration increases, the film weight increases; PO4 content Phosphate film weight has a greater impact, improve PO4. content to increase the phosphate film weight.


2. Alkaline electrolytic polishing process of aluminum

Alkaline polishing solution system research was conducted to compare the effect of corrosion inhibitors, viscosity agents, etc. on the polishing effect. Successfully obtained a good polishing effect of alkaline solution system. And for the first time, we obtained additives that can reduce the operating temperature, extend the service life of the solution, and also improve the polishing effect. The experimental results show that the addition of appropriate additives to NaOH solution can produce a good polishing effect.

The surface reflectivity of aluminum can reach 90% after DC constant voltage electrolytic polishing with NaOH solution of glucose under certain conditions. However, further study is needed because the experiment is still unstable. The feasibility of using the DC pulsed electrolytic polishing method to polish aluminum under alkaline conditions was explored. The results show that: The leveling effect of DC constant voltage electrolytic polishing can be achieved by using the pulse electrolytic polishing method, but its leveling speed is slow.


3. Aluminum and aluminum alloy environmentally friendly chemical polishing

To determine the development of a new environmentally friendly chemical polishing technology with phosphoric acid and sulfuric acid as the base solution. The technology should achieve zero NOx emission 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 solution to replace nitric acid. For this purpose, it is first necessary to analyze the triachemical polishing process of aluminum, with a special focus on the role of nitric acid. The main role of nitric acid in the chemical polishing of aluminum is to inhibit pitting corrosion and improve the brightness of polishing. Combined with the chemical polishing test in the simple phosphoric acid a sulfuric acid, that in the phosphoric acid a sulfuric acid added special substances should be able to inhibit the point corrosion, slow down the overall corrosion. At the same time must have a good leveling and brightness effect


4. Electrochemical surface strengthening treatment of aluminum and its alloys

The process, properties, morphology, composition, and structure of ceramic-like amorphous composite transformation films deposited by anodic oxidation of aluminum and its alloys in a neutral system. The film-forming process and mechanism of the film layers were initially discussed. The results of the process study showed that in the neutral mixed system of Na_2WO_4, the concentration of film-forming accelerator was 2.5-3.0 g/l, the concentration of complexing film-forming agent was 1.5-3.0 g/l, the concentration of Na_2WO_4 was 0.5-0.8 g/l, and the peak current density was 6-12 A/dm~2. Weak stirring could obtain a complete and uniform gray series of the inorganic non-metallic film layers. The film thickness is 5~10μm, microhardness is 300~540HV, and excellent corrosion resistance. The neutral system has good adaptability to aluminum alloys, and it can form films on many series of aluminum alloys such as rust-proof aluminum and wrought aluminum.


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