A chemical polishing method for improving the glossiness of an aluminum alloy surface

Abstract

The application discloses a chemical polishing method for improving the surface gloss of an aluminum alloy, and preparation steps of the method comprise the following steps: (1) adding a mixture of four (4-carboxyphenyl) porphyrin, ethanol, N,N-dimethylformamide and triethylamine into a composite aqueous solution of nickel sulfate and N,N-dimethylformamide, stirring, adding lecithin, and stirring to obtain a mixed solution; (2) uniformly mixing triethanolamine, lactobionic acid and methanol in a reaction kettle, sealing, heating and keeping warm in a nitrogen protection atmosphere, removing methanol by rotary evaporation, adding the residue into the mixed solution, and obtaining a polishing additive; (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, then uniformly mixing the base acid solution, the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate and thiourea to form a chemical polishing solution; and (4) chemical polishing. After the aluminum alloy is polished, the surface gloss of the aluminum alloy is relatively high, and the conventional nitric acid is avoided, zero emission of nitrogen oxides is realized, and the method is green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of metal chemical polishing, in particular to a chemical polishing method for improving the surface glossiness of aluminum alloy. Background Art

[0002] The traditional three-acid polishing process for aluminum and aluminum alloys produces large amounts of yellow nitrogen oxide smoke during polishing due to the large amount of nitric acid in the polishing solution. Furthermore, waste gas treatment during production often fails to meet requirements, causing serious environmental pollution and harming human health. In recent years, nitric acid-free chemical polishing processes have been commonly used to eliminate atmospheric pollution caused by nitrogen oxides generated by chemical polishing. Nitric acid is a strong oxidizing agent with excellent polishing and surface leveling properties. Without nitric acid in the polishing agent, the polishing effect is significantly weakened. Therefore, additives such as surfactants, wetting agents, and corrosion inhibitors must be added to the solution. In other words, appropriate polar group-containing additives must be added to replace the polishing effect of nitric acid. The main concern for the polished product is its surface condition, including surface smoothness, brightness, pitting corrosion, and part weight loss. Regardless of the added substances, they must meet the polishing requirements. Therefore, the current research and development trend is to add certain additives to the nitric acid-free base solution to improve the polishing brightness of aluminum alloys and slow or inhibit pitting corrosion. Summary of the Invention

[0003] To this end, the present invention provides a chemical polishing method for improving the surface gloss of aluminum alloy, the preparation steps comprising:

[0004] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then adding the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide under stirring, stirring for more than 4 hours under ultrasonic environment after the addition is completed, and then adding lecithin, and continuing to stir for more than 2 hours after the addition is completed to obtain a mixed solution;

[0005] (2) adding triethanolamine, lactobionic acid, and methanol to a reactor and mixing them uniformly; then sealing the reactor, filling the reactor with nitrogen to expel the air, so that the reactor is in a nitrogen protective atmosphere; then heating the reactor to 90±3° C. in a water bath and keeping the temperature for more than 10 hours; then air-cooling to room temperature; opening the reactor, and removing the methanol by rotary evaporation in a fume hood; and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0006] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, and then uniformly mixing the base acid solution with the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution;

[0007] (4) The aluminum alloy to be polished is immersed in an acetone solution and ultrasonically cleaned for more than 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution kept at a constant temperature of 85 to 90° C. in a water bath for 2 to 3 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0008] Furthermore, in step (1), in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 10-12 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; and the mixing mass ratio of the components in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine:ethanol:N,N-dimethylformamide:triethylamine=8-10:40-50:5-6:0.2-0.3.

[0009] Furthermore, in the step (1), the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in a ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 8-12 mL: 50 mL: 0.1-0.2 g.

[0010] Furthermore, in the step (2), the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 15-18:10-12:100.

[0011] Furthermore, in step (3), the volume ratio of the mixed concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid:concentrated sulfuric acid=2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%.

[0012] Furthermore, in step (3), the mixing mass ratio of the components of the chemical polishing solution is base acid: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000: 20-30: 0.4-0.5: 9-10: 0.5-0.6: 0.5-0.6: 0.1-0.2.

[0013] The beneficial effects of the present invention are: after polishing the aluminum alloy using the polishing method of the present invention, the surface gloss of the aluminum alloy is high, and there are no obvious visible pitting pits, the polishing effect is good, and the conventional use of nitric acid is avoided, achieving zero emission of nitrogen oxides, which is green and environmentally friendly. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the embodiments.

[0015] Example 1

[0016] A chemical polishing method for improving the surface gloss of an aluminum alloy, the preparation steps comprising:

[0017] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 10 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 8:40:5:0.2; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then stirring In the state, the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and the mixture is stirred for 4 hours under an ultrasonic environment after the addition is completed, and then lecithin is added. The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 8 mL: 50 mL: 0.1 g; after the addition is completed, stirring is continued for 2 hours to obtain a mixed solution;

[0018] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them uniformly, wherein the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 15:10:100; then sealing the reactor, filling the reactor with nitrogen to expel the air so that the reactor is in a nitrogen protective atmosphere, then heating the reactor to 90±3°C in a water bath and keeping the temperature for 10 hours, air cooling to room temperature, opening the reactor, and removing the methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0019] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:20:0.4:9:0.5:0.5:0.1;

[0020] (4) The aluminum alloy to be polished (grade 5A02 aluminum alloy, the same aluminum alloy used in each embodiment and comparative example) was immersed in an acetone solution and ultrasonically cleaned for degreasing for 10 minutes. The aluminum alloy was then taken out, rinsed with deionized water to remove the surface acetone, dried, and then sealed with glue to seal the surface that did not need to be polished, leaving only the surface that needed to be polished exposed. The aluminum alloy after glue application was then immersed in the chemical polishing solution kept at a constant temperature of 87±2°C in a water bath for 2 minutes. The aluminum alloy was then taken out, the polished surface was rinsed with deionized water, and dried to complete the chemical polishing of the aluminum alloy surface.

[0021] Example 2

[0022] A chemical polishing method for improving the surface gloss of an aluminum alloy, the preparation steps comprising:

[0023] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 11 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 9:45:5:0.2; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then stirring under stirring The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide under a continuous state, and after the addition is completed, stirring is carried out under an ultrasonic environment for 4 hours, and then lecithin is added. The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 10 mL: 50 mL: 0.1 g; after the addition is completed, stirring is continued for 2 hours to obtain a mixed solution;

[0024] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them uniformly, wherein the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 16:11:100; then sealing the reactor, filling the reactor with nitrogen to expel the air, so that the reactor is in a nitrogen protective atmosphere, then heating the reactor to 90±3°C in a water bath and keeping the temperature for 10 hours, air cooling to room temperature, opening the reactor, and removing the methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0025] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:24:0.4:9:0.5:0.5:0.1;

[0026] (4) The aluminum alloy to be polished (grade 5A02) is immersed in an acetone solution and ultrasonically cleaned for 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution in a water bath kept at a constant temperature of 87±2°C for 2 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0027] Example 3

[0028] A chemical polishing method for improving the surface gloss of an aluminum alloy, the preparation steps comprising:

[0029] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 11 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 9:47:6:0.3; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then stirring under stirring The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide under a continuous state, and after the addition is completed, stirring is carried out under an ultrasonic environment for 4 hours, and then lecithin is added. The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 10 mL: 50 mL: 0.2 g; after the addition is completed, stirring is continued for 2 hours to obtain a mixed solution;

[0030] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them uniformly, wherein the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 17:11:100; then sealing the reactor, filling the reactor with nitrogen to expel the air, so that the reactor is in a nitrogen protective atmosphere, then heating the reactor to 90±3°C in a water bath and keeping the temperature for 10 hours, air cooling to room temperature, opening the reactor, and removing the methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0031] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the mixed volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:28:0.5:10:0.6:0.6:0.2;

[0032] (4) The aluminum alloy to be polished (grade 5A02) is immersed in an acetone solution and ultrasonically cleaned for 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution in a water bath kept at a constant temperature of 87±2°C for 2 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0033] Example 4

[0034] A chemical polishing method for improving the surface gloss of an aluminum alloy, the preparation steps comprising:

[0035] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 12 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 10:50:6:0.3; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then stirring In the state, the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and the mixture is stirred for 4 hours under an ultrasonic environment after the addition is completed. Then, lecithin is added, and the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 12 mL: 50 mL: 0.2 g; after the addition is completed, stirring is continued for 2 hours to obtain a mixed solution;

[0036] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them uniformly, wherein the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 18:12:100; then sealing the reactor, filling the reactor with nitrogen to expel the air so that the reactor is in a nitrogen protective atmosphere, then heating the reactor to 90±3°C in a water bath and keeping the temperature for 10 hours, air cooling to room temperature, opening the reactor, and removing the methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0037] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:30:0.5:10:0.6:0.6:0.2;

[0038] (4) The aluminum alloy to be polished (grade 5A02) is immersed in an acetone solution and ultrasonically cleaned for 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution in a water bath kept at a constant temperature of 87±2°C for 2 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0039] Comparative Example 1

[0040] A comparative method for chemical polishing of aluminum alloy surfaces includes the following steps:

[0041] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 11 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 9:45:5:0.2; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide ... The method further comprises the following steps: adding the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide under stirring, stirring for 4 hours under an ultrasonic environment after the addition is completed, adding the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine = 10 mL:50 mL; continuing to stir for 2 hours after the addition is completed to obtain a mixed solution;

[0042] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them uniformly, wherein the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 16:11:100; then sealing the reactor, filling the reactor with nitrogen to expel the air, so that the reactor is in a nitrogen protective atmosphere, then heating the reactor to 90±3°C in a water bath and keeping the temperature for 10 hours, air cooling to room temperature, opening the reactor, and removing the methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing uniformly to obtain a polishing additive;

[0043] (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:24:0.4:9:0.5:0.5:0.1;

[0044] (4) The aluminum alloy to be polished (grade 5A02) is immersed in an acetone solution and ultrasonically cleaned for 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution in a water bath kept at a constant temperature of 87±2°C for 2 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0045] Comparative Example 2

[0046] A comparative method for chemical polishing of aluminum alloy surfaces includes the following steps:

[0047] (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 11 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 9:45:5:0.2; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then adding the nickel sulfate to the composite aqueous solution under stirring; The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine was added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and the mixture was stirred for 4h under an ultrasonic environment after the addition was completed, and then lecithin was added. The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin were added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of nickel sulfate, N,N-dimethylformamide: tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 10mL:50mL:0.1g; after the addition was completed, stirring was continued for 2h to obtain a mixed solution as a polishing additive for this comparative example;

[0048] (2) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a base acid solution, wherein the mixed volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%; then uniformly mixing the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000:24:0.4:9:0.5:0.5:0.1;

[0049] (3) The aluminum alloy to be polished (grade 5A02) is immersed in an acetone solution and ultrasonically cleaned for 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished, leaving only the surface that needs to be polished exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution in a water bath kept at a constant temperature of 87±2°C for 2 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

[0050] Example 5

[0051] The glossiness of the aluminum alloy surfaces after chemical polishing according to the methods described in the above embodiments and comparative examples was tested using a gloss meter. The test angle was set to 60°. Three different positions of each sample were tested, and the average value was taken as the glossiness of the group of samples.

[0052] As shown in Table 1, after polishing method of the present invention polishes aluminum alloy, aluminum alloy surface glossiness is higher, and there is no obvious pitting pit, polishing effect is good, and avoids conventional nitric acid, realizes zero emission of nitrogen oxides, green environmental protection. As shown in Example 2 of the present application and comparative example, by adding the polishing additive prepared by the present invention, the chemical polishing effect of aluminum alloy can be further improved, and glossiness significantly improves. This is mainly due to the present invention by four (4- carboxyphenyl) porphine and nickel sulfate self-assembly, synthesizes four (4- carboxyphenyl) porphine-nickel ion assembly, the macromolecular nickel complex obtained on the one hand, can to point corrosion and obvious inhibition and mitigation during chemical polishing, while ionization releases nickel ion during chemical polishing, more easily goes out aggregation reduction in pitting pit, slows down the continuation deep corrosion of pitting; and forms galvanic cell structure with the aluminum at the aluminum surface protrusion, accelerates the dissolving at the protrusion, makes aluminum alloy surface more tend to be smooth. Adding lecithin can improve the stability of complex, avoids complex to rapidly decompose the viscosity of polishing solution improving in acid system, makes aluminum dissolution and diffusion slow down, affects polishing effect. Then, lactobionic acid-modified triethanolamine is added, which can be adsorbed on the aluminum surface during the chemical polishing process, effectively reducing the corrosion rate of the aluminum alloy in the polishing liquid and reducing mass loss; and the adsorbed macromolecules are denser in the depressions on the aluminum alloy surface and sparser in the protrusions. This makes the depressions much larger than the protrusions in terms of energy barriers and material transfer barriers during the chemical polishing process, and the corrosion rate is slow in the depressions and fast in the protrusions, which is beneficial to surface smoothing and improving gloss.

[0053] Table 1

[0054] experimental group Gloss (GS) Example 1 609 Example 2 621 Example 3 617 Example 4 614 Comparative Example 1 575 Comparative Example 2 528

[0055] The technical solutions provided by the present invention are described in detail above. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A chemical polishing method for improving the surface gloss of aluminum alloy, characterized in that: The preparation steps include: (1) preparing a composite aqueous solution of nickel sulfate and N,N-dimethylformamide; in the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, the concentration of nickel sulfate is 10-12 g / 100 mL, the mass percentage of N,N-dimethylformamide is 10%, and the solvent is water; preparing a mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine; the mixing mass ratio of each component in the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is tetrakis(4-carboxyphenyl)porphine: ethanol: N,N-dimethylformamide: triethylamine = 8-10:40-50:5-6:0.2-0.3; stirring the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and then stirring In a state, the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine is added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide, and the mixture is stirred for more than 4 hours under an ultrasonic environment after the addition is completed, and then lecithin is added. The mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine and lecithin are added to the composite aqueous solution of nickel sulfate and N,N-dimethylformamide in an amount ratio of the composite aqueous solution of nickel sulfate and N,N-dimethylformamide: the mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 8-12 mL: 50 mL: 0.1-0.2 g; after the addition is completed, stirring is continued for more than 2 hours to obtain a mixed solution; (2) Add triethanolamine, lactobionic acid and methanol into the reactor and mix them evenly. The mass ratio of triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 15-18:10-12:100; then seal the reactor, fill the reactor with nitrogen to expel the air, so that the reactor is in a nitrogen protective atmosphere, then heat the reactor to 90±3°C in a water bath and keep it warm for more than 10 hours, air-cool to room temperature, open the reactor, and remove the methanol by rotary evaporation in a fume hood. The residue is added to the mixed solution and mixed evenly to obtain a polishing additive; (3) Concentrated phosphoric acid and concentrated sulfuric acid are uniformly mixed to form a base acid solution, and then the base acid solution and the polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea are uniformly mixed to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is base acid solution: polishing additive: hexanoic acid: ammonium persulfate: sodium polyphosphate: sodium diphenylamine sulfonate: thiourea = 1000: 20-30: 0.4-0.5: 9-10: 0.5-0.6: 0.5-0.6: 0.1-0.2; (4) The aluminum alloy to be polished is immersed in an acetone solution and ultrasonically cleaned for more than 10 minutes to remove oil. The aluminum alloy is then taken out and rinsed with deionized water to remove the surface acetone. The aluminum alloy is dried and then sealed with glue to seal the surface that does not need to be polished. Only the surface that needs to be polished is exposed. The aluminum alloy after glue application is then immersed in the chemical polishing solution kept at a constant temperature of 85 to 90°C in a water bath for 2 to 3 minutes. The aluminum alloy is then taken out and the polished surface is rinsed with deionized water and dried to complete the chemical polishing of the aluminum alloy surface.

2. The chemical polishing method for improving the surface gloss of aluminum alloy according to claim 1, characterized in that: In the step (3), the mixed volume ratio of the concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of the concentrated phosphoric acid is 85%, and the solute mass percentage of the concentrated sulfuric acid is 98%.