Aluminum castings involve various surface treatment methods, such as aluminum phosphating. Research has shown that guanidine nitrate has good water solubility, low dosage, and rapid film formation, making it an effective promoter for aluminum phosphating. Fluoride can promote film formation, increase film weight, and refine grain size; Mn2+and Ni2+can significantly refine the grain size, make the phosphating film uniform and dense, and improve the appearance of the phosphating film; As the concentration of Zn2+increases, the membrane weight also increases; The PO4 content has a significant impact on the weight of the phosphating film, and increasing the PO4 content increases the weight of the phosphating film.
Next is the alkaline electrolytic polishing process for aluminum, which can produce good polishing effects by adding appropriate additives to NaOH solution. The feasibility of using DC pulse electrolytic polishing method to polish aluminum materials under alkaline conditions shows that the use of pulse electrolytic polishing method can achieve the leveling effect of DC constant voltage electrolytic polishing, but its leveling speed is slow.
The key to environmentally friendly chemical polishing of aluminum castings and aluminum alloys is to add some compounds with special effects to the base solution instead of nitric acid. Firstly, it is necessary to analyze the three acid chemical polishing process of aluminum, with a particular focus on studying the effect of nitric acid.
The main function of nitric acid in aluminum chemical polishing is to suppress pitting corrosion and improve polishing brightness. Based on the chemical polishing test in pure phosphoric acid monosulfate, it is believed that the special substance added to phosphoric acid monosulfate should be able to inhibit pitting corrosion, slow down overall corrosion, and must have good leveling and brightening effects.
The electrochemical surface strengthening treatment of aluminum and its alloys is also one of the surface treatment processes for aluminum castings. In the neutral Na2WO4 mixed system, the concentration of film-forming promoter is controlled at 2.5-3.0g/l, the concentration of complexing 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 weak stirring can obtain a complete, uniform, and glossy gray series inorganic non-metallic film layer.