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It is precisely because of the wide application of aluminum casting technology in modern machinery and industrial sectors that aluminum alloy die-castings are very common. To improve the quality and performance of the workpieces, surface treatment is also required after the aluminum alloy die-castings are formed. There are mainly four methods involved in the conventional approach.

One is the phosphating treatment of aluminum alloy die-castings. Research shows that guanidine nitrate can be used as an effective accelerator for its phosphating due to its good water solubility, low dosage and rapid film formation. Fluoride can promote film formation, increase film weight, refine grains, and has a very good effect on improving the phosphating film on the surface of aluminum alloy die-castings.

Another one is the alkaline electrolytic polishing process for aluminum alloy die-castings. The conversion switch studied and compared the effects of corrosion inhibitors, viscometers, etc. on the polishing effect, thereby obtaining an alkaline solution system with excellent polishing effect, and obtaining additives that can reduce the operating temperature, extend the service life of the solution, and improve the polishing effect at the same time.

Tests have proved that if the direct current constant voltage electrolytic polishing of aluminum alloy die-castings is carried out with NaOH solution of glucose under certain conditions, the surface reflectivity of the castings can reach 90%. However, due to the existence of unstable factors in the experiment, further research is needed.

Another type is the environmentally friendly chemical polishing treatment process for aluminum alloy die-castings. It uses a compound with special functions based on phosphoric acid and sulfuric acid to replace nitric acid, thereby achieving zero NOx emissions and overcoming the quality defects existing in previous similar technologies. The main role of nitric acid in the chemical polishing of aluminum alloy die-castings is to inhibit pitting corrosion and enhance the polishing brightness.

In addition, electrochemical surface strengthening treatment is also a surface treatment process applied to aluminum alloy die-castings. It is a process in which the castings are anodized and deposited in a neutral system and form a ceramic-like amorphous composite transformation film. The results of the process research show that in the neutral mixed system of Na_2WO_4, the concentration of the film-forming accelerator is controlled at 2.5-3.0g/l, the concentration of the complexing 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, and weak stirring is carried out. A complete, uniform and glossy gray series of inorganic non-metallic film layers can be obtained.