The development of a new environmental chemical polishing technology with phosphoric acid as the base liquid is to realize the zero emission of NOx and to overcome the quality defects of the previous similar technologies. The key of the new technology is to add some special compounds in the base fluid instead of nitric acid. Therefore, it is necessary to analyze the chemical polishing process of aluminum at first, especially the role of nitric acid. The main role of nitric acid in aluminum chemical polishing is to inhibit spot corrosion and improve the brightness of polishing. Combined with the chemical polishing test in pure phosphoric acid, it is considered that the special substances added in the phosphoric acid monophosphate should be able to inhibit the point corrosion and reduce the overall corrosion, and have better leveling and brightening effect.

4. Electrochemical surface enhanced treatment of aluminum and its alloys

The process, properties, morphology, composition and structure of the ceramic amorphous composite conversion film formed by anodizing of aluminum and its alloys in the neutral system are discussed. The process and mechanism of film formation are preliminarily discussed. The results show that the concentration of the membrane promoter is 2.5 to 3.0g/l, the concentration of the collaterals is 1.5 to 3.0g/l, the concentration of Na_2WO_4 is 0.5 to 0.8g/l, the peak current density is 6 ~ 12A/dm~2, and the weak stirring is used to obtain the grey series inorganic nonmetal with complete uniformity and good luster. The film layer. The film thickness is 5 ~ 10μ m, the microhardness is 300 ~ 540HV, and the corrosion resistance is excellent. The neutral system has good adaptability to aluminum alloy, and all kinds of aluminum alloys such as rust proof aluminum and Forging Aluminum can be well formed.