Surface Treatment Solutions for Die Casting Aluminum Alloys

Die casting aluminum alloy contains 6.5~7.5% Si, and the high Si content makes the material have good fluidity in the die casting process. Die-cast aluminum has light weight, good mechanical strength, electrical conductivity, good thermal conductivity, non-magnetic, and can use die-casting technology to cast complex parts with high dimensional accuracy. However, the plating adhesion of die-casting aluminum alloy is poor, and the corrosion resistance needs to be improved. Colored zinc plating and chromate treatment can be considered from the cost and function.

• Four Surface Treatment Methods for Aluminum Alloy Die Castings

1. Aluminum phosphating

The effects of accelerators, fluorides, Mn2 +, Ni2 +, Zn2 +, PO4 +, and Fe2 + on the phosphating process of aluminum were studied in detail by means of SEM,XRD, potential-time curves, and film weight changes. The results show that guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation, and is an effective accelerator for aluminum phosphating: fluoride can promote film formation, increase film weight and refine grains; Mn2 and Ni2 can obviously refine grains, make the phosphating film uniform and dense and improve the appearance of the phosphating film; Zn2 concentration is low, film formation or film formation is poor, with the increase of Zn2 concentration, film weight increases; the content of PO4 has a great influence on the weight of phosphating film, and the increase of PO4. The content increases the weight of the 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, and the alkaline solution system with good polishing effect was successfully obtained, and the additives that can reduce the operating temperature, extend 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 in NaOH solution can produce good polishing effect. Exploratory experiments also found that: with glucose NaOH solution in some conditions after DC constant pressure electrolytic polishing, aluminum surface reflectivity can reach 90%, but because of the experimental still exist unstable factors, to be further studied. The feasibility of using DC pulse electrolytic polishing method to polish aluminum under alkaline conditions is explored, and 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 environmental protection chemical polishing

It is determined to develop a new environmentally friendly chemical polishing technology based on phosphoric acid and sulfuric acid, which is to achieve zero emission of NOx and overcome the quality defects of similar technologies in the past. The key of the new technology is to add some compounds with special effects to the base liquid to replace nitric acid. To this end, it is first necessary to analyze the three-acid chemical polishing process of aluminum, with particular emphasis 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 and sulfuric acid, it is believed that the special substances added to phosphoric acid and sulfuric acid should be able to inhibit point corrosion, 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, performance, morphology, composition and structure of the anodic oxidation deposition of aluminum and its alloys in the neutral system to form a ceramic-like amorphous composite conversion film, and the film-forming process and mechanism of the film are discussed. The process research results show that in the Na_2WO_4 neutral mixed system, the concentration of film-forming accelerator is 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/dm ~ 2, weak stirring, can obtain a complete uniform, shiny gray series of inorganic non-metallic film. The thickness of the film is 5~10 μm, the microhardness is 300~540HV, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloy, antirust aluminum, forged aluminum and other series of aluminum alloy can be a good film.

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 can be easily combined with organic coatings to facilitate subsequent surfaces.