Chemical polishing method for improving surface glossiness of aluminum alloy

Abstract

The invention discloses a chemical polishing method for improving surface glossiness of aluminum alloy, which comprises the following steps: (1) adding a mixture of tetra (4-carboxyphenyl) porphin, ethanol, N, N-dimethylformamide and triethylamine into a composite aqueous solution of nickel sulfate, N, N-dimethylformamide, stirring, adding lecithin, and stirring to obtain a mixed solution; (2) adding triethanolamine, lactobionic acid and methanol into a reaction kettle, uniformly mixing, sealing, heating and preserving heat in a nitrogen protection atmosphere, carrying out rotary evaporation to remove methanol, and adding residues into the mixed solution to obtain a polishing additive; (3) uniformly mixing concentrated phosphoric acid and concentrated sulfuric acid to form a basic acid solution, and then uniformly mixing the basic acid solution with a polishing additive, hexanoic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylaminesulfonate and thiourea to form a chemical polishing solution; and (4) chemical polishing. After the aluminum alloy is polished, the surface glossiness of the aluminum alloy is high, nitric acid used conventionally is avoided, zero emission of nitric oxide is achieved, and the aluminum alloy polishing solution is green and environmentally friendly.

Description

Technical Field

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

[0002] The traditional three-acid polishing process for aluminum and aluminum alloys, because the polishing liquid contains a large amount of nitric acid, will produce a large amount of yellow smoke of nitrogen oxides during polishing, and the waste gas treatment in production often fails to meet the requirements, seriously polluting the environment and endangering human health. In recent years, a nitric acid-free chemical polishing process is often used to eliminate the pollution of nitrogen oxides produced by chemical polishing to the atmosphere. Nitric acid is a strong oxidant with good polishing and surface leveling effects. If there is no nitric acid in the polishing agent, the polishing effect will be significantly weakened. Therefore, additives such as surfactants, wetting agents, and corrosion inhibitors must be added to the solution, that is, appropriate additives containing polar groups are added to replace the polishing effect of nitric acid. For the polished product, the main concern is its surface state, including: surface flatness, brightness, pitting degree and part weight loss rate, etc. No matter what substance is added, it must meet the polishing requirements. Therefore, the current research and development trend is to add certain additives to the nitric acid-free base liquid to improve the polishing brightness of aluminum alloys and slow down or inhibit pitting. Summary of the invention

[0003] To this end, the present invention provides a chemical polishing method for improving the glossiness of the aluminum alloy surface, 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 into a reactor and mixing them evenly, 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, 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 evenly to obtain a polishing additive;

[0006] (3) mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic acid solution, and then uniformly mixing the basic acid solution and the polishing additive, caproic 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 to remove oil for more than 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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, the polished surface is rinsed with deionized water, and dried to complete the chemical polishing of the aluminum alloy surface.

[0008] Furthermore, in the 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; 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 the ratio of composite aqueous solution of nickel sulfate and N,N-dimethylformamide: 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 mixed volume ratio of concentrated phosphoric acid and concentrated sulfuric acid is concentrated phosphoric acid: concentrated sulfuric acid = 2:1, wherein the solute mass percentage of concentrated phosphoric acid is 85%, and the solute mass percentage of concentrated sulfuric acid is 98%.

[0012] Furthermore, in the step (3), the mixing mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 effect of the present invention is that after the aluminum alloy is polished by 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 in conjunction with the embodiments.

[0015] Example 1

[0016] A chemical polishing method for improving the glossiness of aluminum alloy surface, 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 after the addition is completed, the mixture is stirred for 4 hours under an ultrasonic environment, 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 = 8mL: 50mL: 0.1g; 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 evenly, wherein the mass ratio of 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 for 10 h, air cooling to room temperature, opening the reactor, removing methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing evenly to obtain a polishing additive;

[0019] (3) Mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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) is immersed in an acetone solution and ultrasonically cleaned to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, the polished surface is 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 glossiness of aluminum alloy surface, 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 state, and after the addition is completed, the mixture is stirred for 4 hours under an ultrasonic environment, 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 reaction kettle and mixing them evenly, wherein the mass ratio of triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 16:11:100; then sealing the reaction kettle, filling the reaction kettle with nitrogen to expel the air, so that the reaction kettle is in a nitrogen protective atmosphere, then heating the reaction kettle to 90±3° C. in a water bath and keeping the temperature for 10 h, air cooling to room temperature, opening the reaction kettle, and removing methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing evenly to obtain a polishing additive;

[0025] (3) mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, 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 glossiness of aluminum alloy surface, 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 state, and after the addition is completed, the mixture is stirred for 4 hours under an ultrasonic environment, 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 evenly, wherein the mass ratio of 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 for 10 h, air cooling to room temperature, opening the reactor, and removing methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing evenly to obtain a polishing additive;

[0031] (3) Mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, 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 glossiness of aluminum alloy surface, 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 after the addition is completed, the mixture is stirred for 4 hours under an ultrasonic environment, 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 = 12mL: 50mL: 0.2g; after the addition is completed, stirring is continued for 2h to obtain a mixed solution;

[0036] (2) adding triethanolamine, lactobionic acid and methanol to a reactor and mixing them evenly, wherein the mass ratio of 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 for 10 h, air cooling to room temperature, opening the reactor, and removing methanol by rotary evaporation in a fume hood, and adding the residue to the mixed solution and mixing evenly to obtain a polishing additive;

[0037] (3) Mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixing mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, 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 surface comprises 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; stirring is continued for 2 hours after the addition is completed to obtain a mixed solution;

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

[0043] (3) mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, 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 surface comprises 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 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 nickel sulfate, N,N-dimethylformamide composite aqueous solution: mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 10mL: 50mL: 0.1g; after the addition is completed, stirring is continued for 2h to obtain a mixed solution as a polishing additive for this comparative example;

[0048] (2) mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic 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 mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea uniformly to form a chemical polishing solution; the mixed mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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 to remove oil for 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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 87±2°C in a water bath for 2 minutes. The aluminum alloy is then taken out, 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 the polishing method of the present invention polishes aluminum alloy, the aluminum alloy surface glossiness is high, and there is no obvious pitting pit, the polishing effect is good, and the conventional nitric acid is avoided, and the zero emission of nitrogen oxides is achieved, which is green and environmentally friendly. As shown in Example 2 of the present application and the comparative example, by adding the polishing additive prepared by the present invention, the chemical polishing effect of aluminum alloy can be further improved, and the glossiness is significantly improved. This is mainly due to the fact that the present invention is self-assembled by tetrakis (4-carboxyphenyl) porphine and nickel sulfate, and tetrakis (4-carboxyphenyl) porphine-nickel ion assembly is synthesized, and the macromolecular nickel complex obtained on the one hand can inhibit and alleviate pitting corrosion in the chemical polishing process, and release nickel ions during chemical polishing, and it is easier to aggregate reduction in pitting pits, and slow down the continued deep corrosion of pitting; and the aluminum at the protrusion of the aluminum surface forms a galvanic cell structure, accelerates the dissolution of the protrusion, and makes the aluminum alloy surface more smooth. Adding lecithin can improve the stability of the complex, avoid the complex from rapidly decomposing the viscosity of the polishing liquid in the acid system, slow down the dissolution and diffusion of aluminum, and affect the 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. The corrosion rate is slow in the depressions and fast in the protrusions, which is beneficial to surface smoothing and improving glossiness.

[0053] Table 1

[0054] Experimental Group Glossiness(GS) Example 1 609 Example 2 621 Example 3 617 Example 4 614 Comparative Example 1 575 Comparative Example 2 528

[0055] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A chemical polishing method for improving the glossiness of aluminum alloy surface. It is characterized in that The preparation steps include: (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; (2) adding triethanolamine, lactobionic acid and methanol into a reactor and mixing them evenly, 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, 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 evenly to obtain a polishing additive; (3) mixing concentrated phosphoric acid and concentrated sulfuric acid uniformly to form a basic acid solution, and then uniformly mixing the basic acid solution and the polishing additive, caproic acid, ammonium persulfate, sodium polyphosphate, sodium diphenylamine sulfonate, and thiourea to form a chemical polishing solution; (4) The aluminum alloy to be polished is immersed in an acetone solution and ultrasonically cleaned to remove oil for more than 10 minutes. The aluminum alloy is then taken out, rinsed with deionized water to remove the surface acetone, 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, the polished surface is rinsed with deionized water, and dried to complete the chemical polishing of the aluminum alloy surface.

2. A chemical polishing method for improving the surface gloss of aluminum alloy according to claim 1, It is characterized in that In the 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; 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.

3. A chemical polishing method for improving the surface gloss of aluminum alloy according to claim 2, It is characterized in that 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 the ratio of composite aqueous solution of nickel sulfate and N,N-dimethylformamide: mixture of tetrakis(4-carboxyphenyl)porphine, ethanol, N,N-dimethylformamide and triethylamine: lecithin = 8-12 mL: 50 mL: 0.1-0.2 g.

4. A chemical polishing method for improving the surface gloss of aluminum alloy according to claim 1, It is characterized in that In the step (2), the mass ratio of the triethanolamine, lactobionic acid and methanol is triethanolamine: lactobionic acid: methanol = 15-18:10-12:

100.

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

6. A chemical polishing method for improving the surface gloss of aluminum alloy according to claim 5, It is characterized in that In the step (3), the mixing mass ratio of the components of the chemical polishing solution is basic acid solution: polishing additive: caproic 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.