What are the surface treatment methods for aluminum alloy die castings? According to the knowledge of the quick screen editor, the commonly used technologies are: aluminum phosphating, alkaline electrolytic polishing process of aluminum, environment-friendly chemical polishing of aluminum and aluminum alloys, electrochemical surface strengthening treatment of aluminum and its alloys, and YL112 aluminum alloy surface treatment technology. The details are as follows:
1. Aluminum phosphating
The accelerant, fluoride, Mn2+, Ni2+, Zn2+, PO4 were studied in detail by means of SEM, XRD, potential time curve and membrane weight change; And Fe2+on the phosphating process of aluminum. Research shows:
Guanidine nitrate is an effective accelerator for aluminum phosphating due to its good water solubility, low dosage and fast film formation; Fluoride can promote film formation, increase film weight and refine grains; Mn2+, Ni2+, can obviously refine the grains, make the phosphating film uniform and compact, and improve the appearance of the phosphating film; When the concentration of Zn2+is low, the film cannot be formed or the film is poor. With the increase of the concentration of Zn2+, the film weight increases; The content of PO4 has a great influence on the weight of phosphating film. Increasing the content of PO4 will increase 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 proper additives in NaOH solution can produce good polishing effect.
The exploratory experiment also found that the reflectivity of aluminum surface could reach 90% after DC constant voltage 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 electropolishing method to polish aluminum under alkaline conditions is explored. The results show that the pulse electropolishing method can achieve the leveling effect of DC constant voltage electropolishing, but the leveling speed is slow.
3. Environmentally friendly chemical polishing of aluminum and aluminum alloy
It is determined to develop a new environment-friendly chemical polishing technology with phosphoric acid sulfuric acid as the base liquid. This technology should achieve 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 tri acid chemical polishing process of aluminum, especially the role of nitric acid. The main role of nitric acid in aluminum chemical polishing is to inhibit spot corrosion and improve polishing brightness. Combined with the chemical polishing test in simple phosphoric acid sulfuric acid, it is considered that the special substances added in phosphoric acid sulfuric acid should be able to inhibit spot corrosion, slow down overall corrosion, and must have good leveling and brightening effects.
4. Electrochemical surface strengthening treatment of aluminum and its alloys
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 process research results show that in the neutral mixed system of Na2WO4, the concentration of film forming accelerator is 2.5-3.0g/l, the concentration of complexing film agent is 1.5-3.0g/l, the concentration of Na2WO4 is 0.5-0.8g/l, the peak current density is 6-12A/dm2, and the weak stirring can obtain a complete and uniform gray series inorganic non-metallic film with good luster. The film thickness is 5-10 μ m. The micro hardness 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 rust proof aluminum and 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 be combined with organic coating to facilitate subsequent surface treatment.