When it comes to aluminum castings, the quality of aluminum alloy materials and the casting process can affect the appearance of a casting. Aluminum castings do not come down from the production line to have a glamorous appearance! The surface treatment of aluminum castings is a very critical link. Today, I will introduce several surface treatment processes for you, and I hope to help you!
1. Phosphating of aluminum castings
The effects of accelerators, fluorides, Mn2+, Ni2+, Zn2+, PO and Fe2+ on the phosphating process of aluminum castings are studied in detail by using SEM, XRD, potential-time curve, film weight change and other methods. Studies have shown that guanidine nitrate has the characteristics of good water solubility, low dosage and rapid film formation. It is an effective accelerator for the phosphating of aluminum castings. Fluoride can promote film formation, increase film weight, and refine grains: Mn2+, Ni2 can be significantly finer Crystal grains, make the phosphating film uniform and compact, and improve the appearance of the phosphating film: when the Zn2+ concentration is low, the film cannot be formed or the film formation is poor. As the Zn2+ concentration increases, the film weight increases: PO4 contains the phosphate film Heavy impact is greater, increase PO4. The content increases the weight of the phosphating film.
2. Alkaline electrolytic polishing process for aluminum castings
Conducted research on alkaline polishing solution system, compared the effects of corrosion inhibitors, viscosity agents, etc. on the polishing effect, and successfully obtained an alkaline solution system with good polishing effects, and for the first time obtained the ability to reduce the operating temperature and prolong the use of the solution. Additives that improve the longevity of the polishing effect at the same time. The experimental results show that adding appropriate additives to the NaOH solution can produce a good polishing effect. Exploratory experiments also found that after DC constant pressure electrolytic polishing with glucose NaOH solution under certain conditions, the surface reflectivity of aluminum castings can reach 90%, but due to the unstable factors in the experiment, further research is needed. The feasibility of using DC pulse electrolytic polishing method to polish aluminum under alkaline conditions is explored. 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.
Three, environmentally friendly chemical polishing of aluminum castings
Determine the development of a new environmentally friendly chemical polishing technology using phosphoric acid-sulfuric acid as the base fluid. This technology must achieve zero emission of NOx and overcome the qualitative defects of similar technologies in the past. The key to the new technology is to add some special effects to the base fluid. Compounds to replace nitric acid. For this reason, it is necessary to analyze the triacid chemical polishing process of aluminum castings, especially the role of nitric acid. The main function of nitric acid in the chemical polishing of aluminum castings is to inhibit pitting corrosion and improve polishing brightness. Combined with the chemical polishing test in simple phosphoric acid-sulfuric acid, it is believed that the special substances added in phosphoric acid-sulfuric acid should be able to inhibit pitting corrosion, salty corrosion, and corrosion. At the same time, it must have a good leveling and brightening effect.
Fourth, electrochemical surface strengthening treatment of aluminum castings
The process, performance, morphology, composition and structure of ceramic-like amorphous composite conversion coating formed by anodic oxidation and deposition of aluminum castings in a neutral system, and the film formation process and mechanism of the coating are preliminarily discussed. Process research results show that in the Na2WO_4 neutral mixing system, the concentration of film-forming accelerator is controlled to be 2.5~3.0g/, the concentration of complexing film agent is 15~3.0g/L, and the concentration of Na_2WO_ 4 is 0.5~0.8g /L, the peak current density is 6~12A/dm~2, weak agitation, a complete and uniform gray series inorganic non-metallic film with good gloss can be obtained. The thickness of the film is 5-10μm, the microhardness is 300-540HV, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloys, and can form a good film on various series of aluminum alloys such as anti-rust aluminum and forged aluminum.
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