The electroplating of die-cast aluminum parts requires special pre-treatment due to the special properties of aluminum. These pre-treatments need to be adjusted due to different aluminum materials and different parts. It is not easy to follow the general process.
There are four common methods for die-casting aluminum parts:
The effects of promoter, fluoride, Mn2+, Ni2+, Zn2+, PO4, and Fe2+ on the phosphating process of aluminum were studied by SEM, XRD, potential-time curve and membrane weight change. Studies have shown that cerium nitrate has the characteristics of good water solubility, low dosage and rapid film formation, and is an effective accelerator for phosphating of aluminum: fluoride can promote film formation, increase membrane weight and refine grains; Mn2+, Ni2+ can be obvious Refinement of crystal grains makes the phosphating film uniform and dense and can improve the appearance of the phosphating film; when the concentration of Zn2+ is low, film formation or film formation is not good. As the concentration of Zn2+ increases, the film weight increases the O4 content to the phosphating film. The impact is greater and the PO4 is improved. The content causes the phosphating film to increase in weight.
Aluminum alkaline electropolishing process
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. The alkaline solution system with good polishing effect of zinc-aluminum die-castings was successfully obtained, and the operating temperature was reduced for the first time. An additive that extends the life of the solution while also improving the polishing effect. The experimental results show that adding a suitable additive to the NaOH solution can produce a good polishing effect. Exploratory experiments also found that the surface reflectance of die-casting aluminum motor casing can reach 90% after DC constant pressure electropolishing with NaOH solution of glucose under certain conditions, but there are still unstable factors in the experiment, which needs further study. The feasibility of using DC pulse electropolishing method to polish aluminum under alkaline conditions was explored. The results show that the pulse electropolishing method can achieve the leveling effect of DC constant pressure electropolishing, but its flattening speed is slow.
Aluminum and aluminum alloy environmentally friendly chemical polishing
It is determined to develop a new environmentally friendly chemical polishing technology based on phosphoric acid monosulfate, which is to 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 special-effect compounds to the base fluid instead of nitric acid. To this end, it is first necessary to analyze the chemical polishing process of aluminum lamp housing triacid, especially the role of nitric acid. The main role of nitric acid in the chemical polishing of aluminum is to suppress pitting corrosion and improve polishing brightness. Combined with the chemical polishing test in simple mono-phosphoric acid, it is considered that the special substances added in the mono-phosphoric acid should be able to suppress pitting corrosion and alleviate general corrosion, and must have good leveling and brightening effects.
Die Casting Parts
Electrochemical surface strengthening treatment of aluminum and its alloys
The process, properties, morphology, composition and structure of aluminum-based alloys in the neutral system were formed by anodization and deposition. The film formation process and mechanism of the film were preliminarily discussed. The results of the process research indicated that in the neutral mixed system of Na_2WO_4, the concentration of the film-forming accelerator was controlled to 2.5-3.0 g/l, the concentration of the complex membrane was 1.5-3.0 g/l, and the concentration of Na_2WO_4 was 0.5-0.8 g/l. The peak current density is 6~12A/dm~2, and the weak agitation can obtain a complete and uniform gray series inorganic non-metal film layer. The film layer has a thickness of 5 to 10 μm and a microhardness of 300 to 540 HV, and is excellent in corrosion resistance. The neutral system has good adaptability to aluminum alloys, and various types of aluminum alloys such as rust-proof aluminum and forged aluminum can form a good film.