5 kinds of surface treatment methods for common aluminum alloy die castings



Many tech houses are very interested in how the surface of aluminum alloy die castings can be smooth and frosted, and how aluminum alloys can make such a curved surface. Today, Xiaobian will introduce common metal castings to you. 5 surface treatment methods.


Method 1: Aluminum phosphating


The effects of accelerator, fluoride, Mn2+, Ni2+, Zn2+, PO4; and Fe2+ on the phosphating process of aluminum were studied in detail by means of SEM, XRD, potential-time curve, and film weight change. Studies have shown that guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation, and is an effective accelerator for phosphating of aluminum materials: fluoride can promote film formation, increase film weight, and refine grains; Mn2+, Ni2+, can The grains are obviously refined to make the phosphating film uniform and dense, and the appearance of the phosphating film can be improved; when the Zn2+ concentration is low, the film cannot be formed or the film formation is poor. With the increase of the Zn2+ concentration, the film weight increases; The film weight has a greater impact and increases PO4. The content increases the weight of the phosphating film.


Method 2: Alkaline Electropolishing Process of Aluminum


The research on the alkaline polishing solution system was carried out, and the effects of corrosion inhibitors and viscosity agents on the polishing effect were compared, and an alkaline solution system with good polishing effect was successfully obtained. Additives that improve longevity while also improving polishing results. The experimental results show that adding appropriate additives in NaOH solution can produce good polishing effect.


The exploratory experiment also found that the reflectivity of the aluminum surface can reach 90% after DC electropolishing with NaOH solution of glucose under certain conditions. However, due to the unstable factors in the experiment, further research is needed. The feasibility of using DC pulse electrolytic polishing method to machining aluminum under alkaline conditions was explored. The results show that the use of pulse electrolytic polishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but its leveling speed is slow.


  1. Environmentally friendly chemical polishing of aluminum and aluminum alloys


Determined to develop a new environmentally friendly chemical polishing technology with phosphoric acid-sulfuric acid as the base fluid, which should achieve zero emission of NOx and overcome the quality defects of previous similar technologies. The key to the new technology is to add some compounds with special effects to the base fluid to replace nitric acid. To this end, it is first necessary to analyze the triacid chemical polishing process of aluminum, especially the effect of nitric acid. The main function of nitric acid in chemical polishing of aluminum 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, slow down general corrosion, and must have better leveling and brightening effects.


Method 4: Electrochemical surface strengthening of aluminum and its alloys


The process, properties, morphology, composition and structure of ceramic-like amorphous composite conversion coatings formed by anodic oxidation deposition of aluminum and its alloys in neutral systems were preliminarily discussed.


The process research results show that in the Na_2WO_4 neutral mixed system, the concentration of the film-forming accelerator is controlled to be 2.5~3.0g/l,


The concentration of complex film forming agent is 1.5~3.0g/l, the concentration of Na_2WO_4 is 0.5~0.8g/l, the peak current density is 6~12A/dm2, and weak stirring can obtain a complete, uniform and glossy gray series inorganic non-ferrous metals. metal film. The film thickness is 5-10 μm, 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.


Method 5: YL112 aluminum alloy surface treatment technology


YL112 aluminum alloy is widely used in structural parts of automobiles and motorcycles. The material requires a surface treatment prior to application to improve its corrosion resistance and to form a surface layer that readily bonds with organic coatings to facilitate subsequent surfaces.

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