Aluminum alloy die-casting products are mainly used in electronics, automobile, motor, home appliances and some communication industries. Some high-quality products with high performance, high precision and high toughness are also used in large aircraft, ships and other industries with high requirements. Generally, five processes are used for surface treatment of aluminum alloy die-casting.
The effects of accelerants, fluorides, 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. The results show that guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation, which is an effective promoter for aluminum phosphating: fluoride can promote film formation, increase film weight and refine grains; Mn2 +, Ni2 + can obviously refine grains, make phosphating film uniform and dense, and improve the appearance of phosphorized film; when Zn2 + concentration is low, it can not form film or poor film formation, with the increase of Zn2 + concentration, aluminum alloy profiles The weight of the phosphating film increased with the increase of PO4 content. The weight of phosphating film increased with the content.
Alkaline Electropolishing of aluminum
The basic polishing solution system was studied, and the effects of corrosion inhibitor and viscosity agent on the polishing effect were compared. The basic polishing 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 good polishing effect can be obtained by adding proper additives into NaOH solution. It is also found that the reflectivity of aluminum surface can reach 90% after 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 polishing aluminum in alkaline condition by DC pulse electropolishing is explored. The results show that DC constant voltage electropolishing can achieve the leveling effect, but its leveling speed is slow.
Environmental friendly chemical polishing of aluminum and aluminum alloy profiles
It is determined to develop a new environmentally friendly chemical polishing technology based on phosphoric acid and sulfuric acid. The technology should achieve zero NOx emission and overcome the quality defects of previous similar technologies. The key of the new technology is to add some compounds with special functions to the base solution to replace nitric acid. Therefore, it is necessary to analyze the chemical polishing process of aluminum, especially the role of nitric acid. The main function of nitric acid in the chemical polishing of aluminum is to restrain the spot corrosion and improve the brightness of polishing. Combined with the chemical polishing test in pure phosphoric acid and sulfuric acid, it is considered that the special substances added in phosphoric acid and sulfuric acid should be able to inhibit the spot corrosion and slow down the overall corrosion, at the same time, it must have a better leveling and bright effect.
Electrochemical surface strengthening of aluminum and its alloys
The process, properties, morphology, composition and structure of ceramic like amorphous composite conversion film formed by anodizing of aluminum and its alloy in neutral system were discussed. The results show that in the neutral mixed system of nazhu2wo ﹤ 4, the concentration of film-forming promoter is 2.5-3.0g/l, the concentration of complexing agent is 1.5-3.0g/l, the concentration of nazhu2wo ﹤ 4 is 0.5-0.8g/l, the peak current density is 6-12a / DM ~ 2, and the gray series inorganic non-metallic films with good luster can be obtained by weak stirring. The thickness of the film is 5-10 μ m, the microhardness is 300-540hv, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloy profiles, and film can be formed on various series of aluminum alloy profiles, such as antirust aluminum, forged aluminum, etc.
Surface treatment technology of aluminum alloy casting
Aluminum alloy castings are 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 which is easy to combine with organic coating to facilitate the subsequent surface.