A method for preparing aluminum alloy corrosion-resistant composite coating

Abstract

The present invention relates to a method for preparing an aluminum alloy corrosion-resistant composite coating, and belongs to the technical field of aluminum alloy processing. First, sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate, and sodium hydroxide in a specific proportion are mixed and configured into a micro-arc oxidation solution, and the pretreated aluminum alloy is subjected to micro-arc oxidation treatment to form a black micro-arc oxidation coating. Subsequently, multi-walled carbon nanotubes are treated with potassium permanganate and hydrogen peroxide, and zinc elements are introduced into the carbon nanotubes. The carbon nanotubes are combined with graphene oxide by ball milling treatment, and a silane coupling agent KH560 is added to further enhance the compatibility to obtain a composite filler. The composite filler is mixed with an aqueous acrylic resin emulsion, an aqueous polyurethane emulsion, etc. to obtain an electrophoretic coating, and the aluminum alloy after micro-arc oxidation is subjected to electrophoretic deposition treatment to obtain a composite coating. The aluminum alloy corrosion-resistant composite coating prepared by the present invention has excellent absorbance and good corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy processing and relates to a method for preparing an aluminum alloy corrosion-resistant composite coating. Background Art

[0002] Aluminum alloys are widely used as structural parts in various equipment due to their excellent performance. Although they have problems such as low surface hardness and poor corrosion resistance, surface treatment through anodizing, painting, electrophoresis technology and micro-arc oxidation technology can significantly improve their corrosion resistance and surface hardness, thereby expanding their use scenarios. In spectral equipment, the core lies in the control of the light beam. The light beam is converted into an effective light beam through various optical elements, and the accuracy of the light beam control must reach the micro-nano level. During this period, part of the light beam will be dispersed, and the light will not disappear or be collected out of thin air. Therefore, the separated light beam needs to be absorbed by the surrounding objects and not reflected back into the effective light beam, thereby interfering with the accuracy or resolution of the effective light beam. If the surface of the part with fixed optical elements can absorb a large amount of separated invalid light beams until the invalid light is not enough to affect the effective light beam, more reliable control of the effective light beam can be achieved, and the interference of the invalid light beam can be greatly reduced. Therefore, it has become an important research direction to make the surface of aluminum alloy parts have both excellent absorbance and good corrosion resistance. Summary of the invention

[0003] The object of the present invention is to provide a method for preparing an aluminum alloy corrosion-resistant composite coating, which has the characteristics of excellent absorbance and good corrosion resistance.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for preparing an aluminum alloy corrosion-resistant composite coating, the specific steps of the preparation method are as follows:

[0006] S1-1: The aluminum alloy surface was polished with 600# water-abrasive sandpaper, and then the polished aluminum alloy was immersed in an alkaline cleaning solution and ultrasonicated at 50-70 °C for 10 min, then immersed in a 75% mass fraction ethanol solution and ultrasonicated for 30 min, and then dried in a vacuum drying oven at 100 °C for 12 h to obtain the pretreated aluminum alloy;

[0007] S1-2: Sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate and sodium hydroxide are mixed and added into deionized water to prepare a micro-arc oxidation solution, and the pretreated aluminum alloy is placed in the micro-arc oxidation solution at 25-35 ℃ for micro-arc oxidation treatment, wherein the pretreated aluminum alloy is used as the anode and the stainless steel plate is used as the cathode. After the treatment, the aluminum alloy is washed with deionized water and dried in a vacuum drying oven at 80 ℃ for 4-6 hours to obtain a micro-arc oxidation coating;

[0008] S1-3: Aqueous acrylic resin emulsion, aqueous polyurethane emulsion, composite filler, blocked isocyanate, polydimethylsiloxane and deionized water are mixed to prepare electrophoretic coating, and the aluminum alloy after micro-arc oxidation is placed in an electrophoretic tank for electrophoretic deposition treatment, wherein the cathode material is the aluminum alloy after micro-arc oxidation, and the anode is stainless steel. After completion, the coating is washed with deionized water and placed in an oven at 160-180°C for curing for 20-40 min to obtain the corrosion-resistant composite coating.

[0009] As a preferred technical solution of the present invention, the composition of the alkaline washing solution in S1-1 is 20-30 g / L sodium hydroxide, 40-50 g / L baking soda, and 1-2 g / L sodium diisooctyl sulfosuccinate, and the solvent of the alkaline washing solution is deionized water.

[0010] As a preferred technical solution of the present invention, the concentrations of the components in the micro-arc oxidation solution in S1-2 are 15-20 g / L sodium phosphate, 10-15 g / L sodium silicate, 10-15 g / L sodium fluoride, 5-10 g / L ammonium metavanadate, 5-10 g / L sodium molybdate, and 7-8 g / L sodium hydroxide.

[0011] As a preferred technical solution of the present invention, a constant current control method is adopted during the micro-arc oxidation reaction in S1-2, and the current density is 2.5~3.5 A / dm 2 , the frequency range is 1000~1500 Hz, the duty cycle is 25~35%, and the time is 20~50 min.

[0012] As a preferred technical solution of the present invention, the thickness of the micro-arc oxidation coating in S1-2 is 6-10 μm.

[0013] As a preferred technical solution of the present invention, the mass proportions of the components in the electrophoretic coating in S1-3 are 30%~40% of aqueous acrylic resin emulsion, 20%~30% of aqueous polyurethane emulsion, 5%~15% of composite filler, 3%~5% of blocked isocyanate, 1%~2% of polydimethylsiloxane, and the balance of deionized water.

[0014] As a preferred technical solution of the present invention, the steps for preparing the composite filler in S1-3 are as follows:

[0015] S7-1: In parts by weight, 5-15 parts of multi-walled carbon nanotubes were added to 100 parts of deionized water, mixed, and ultrasonicated for 30 minutes, and 3-5 parts of a mixture of potassium permanganate and hydrogen peroxide were added, ultrasonicated for 1.5 hours, washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A;

[0016] S7-2: 10-20 parts of powder A were added to 100 parts of deionized water, ultrasonically dispersed for 30 min, 5 parts of 5 mM zinc nitrate solution were added dropwise at a stirring speed of 600-700 r / min, ultrasonicated for 30 min, the pH of the solution was adjusted to 9.5-10.5 with 0.1 M sodium hydroxide, 10-20 parts of hydrazine hydrate were added, ultrasonicated for 10 min, transferred to a reactor and heated at 120 °C for 2 h, then washed with deionized water and anhydrous ethanol, and dried in a -50 °C freeze dryer for 12 h to obtain powder B;

[0017] S7-3: Powder B and graphene oxide were mixed and placed in a ball mill for ball milling for 1 h at a ball milling speed of 150-250 r / min, 3-5 wt% of silane coupling agent KH560 was added, the ball milling speed was increased to 300-400 r / min and the ball milling was continued for 1 h to obtain the composite filler.

[0018] As a preferred technical solution of the present invention, the electrophoretic deposition in S1-3 is carried out in a DC constant voltage mode, the temperature of the electrophoretic tank is 30±0.5°C, the voltage is controlled to increase to 220 V within 15 s, and the deposition time is 2~3 min.

[0019] As a preferred technical solution of the present invention, the potassium permanganate and hydrogen peroxide in S7-1 are mixed in a mass ratio of 1:1.

[0020] As a preferred technical solution of the present invention, the powder B and graphene oxide in S7-3 are mixed in a mass ratio of (1-3):1.

[0021] Pre-treat the surface of the aluminum alloy and use 600# water-abrasive sandpaper to polish the surface of the aluminum alloy, which can effectively remove surface dirt, oxide layer and minor defects. Then soak the aluminum alloy in alkaline washing solution for ultrasonic treatment. Sodium hydroxide and baking soda as a mixture of strong and weak bases can effectively neutralize the acidic substances on the surface of the aluminum alloy, while providing the necessary alkaline environment to promote the decomposition of grease and dirt. Sodium diisooctyl sulfosuccinate as a surfactant can reduce the surface tension of the solution and enhance the cleaning effect; at the same time, ultrasonic action can enhance the cleaning effect and ensure a cleaner surface. Further use of ethanol can further remove residual moisture and some organic matter on the surface. Drying in a vacuum drying oven can completely remove moisture from the surface of the aluminum alloy, ensuring that the surface is dry and residue-free.

[0022] As an innovative surface treatment process, micro-arc oxidation brings many beneficial effects by constructing a ceramic-like hard oxide layer on the surface of the material. Black micro-arc oxidation technology is used to enhance the surface absorbance and corrosion resistance of aluminum alloys. Micro-arc oxidation is an environmentally friendly surface treatment technology that meets the current requirements of green production. The electrolyte system and other related parameters used in the micro-arc oxidation experiment of the present invention, sodium phosphate as the main salt, sodium fluoride as an additive, ammonium metavanadate and sodium molybdate as coloring salts, and sodium hydroxide to adjust the pH of the solution, the purpose is to prepare a black micro-arc oxidation coating with a thickness of 6~10 μm and good bonding with the substrate on the surface of the aluminum alloy; at the same time, the micro-arc oxidation coating prepared by the present invention is conducive to the adhesion of subsequent electrophoretic coatings.

[0023] By mixing potassium permanganate and hydrogen peroxide in a certain mass ratio to oxidize multi-walled carbon nanotubes, oxygen-containing functional groups such as carboxyl and hydroxyl groups can be introduced on the surface of carbon nanotubes. These functional groups help to improve the dispersibility of carbon nanotubes in the coating and the bonding force with the substrate; oxidation treatment can also improve the surface properties of carbon nanotubes, making it easier to form a strong chemical bond with other fillers and coating matrix, thereby enhancing the overall corrosion resistance of the coating. Zinc, as an active metal, has good electrochemical protection properties. The introduction of zinc elements into carbon nanotubes can form zinc compounds or zinc deposits. These zinc compounds or deposits can act as sacrificial anodes in corrosive environments and preferentially undergo corrosion reactions, thereby protecting the aluminum alloy substrate from corrosion; the addition of zinc can also improve the density and hardness of the coating, further blocking the penetration of corrosive media.

[0024] Multi-walled carbon nanotubes and graphene oxide are formed into composite fillers through ball milling. Both multi-walled carbon nanotubes and graphene oxide are excellent light absorbing materials. Multi-walled carbon nanotubes have a one-dimensional structure and have efficient light absorption performance; while graphene oxide has a two-dimensional structure, and its large specific surface area and unique electronic structure make it highly sensitive to light. The combination of these two materials can significantly improve the absorbance of the coating, so that the coating can better absorb light energy under light, and extend the service life of the coating and the substrate. Multi-walled carbon nanotubes and graphene oxide form an intricate network structure in the coating, which can effectively block the penetration of corrosive media, thereby slowing down or preventing the occurrence of the corrosion process. The addition of composite fillers can enhance the interaction force inside the coating, make the coating denser, reduce the pores and defects in the coating, and further improve the anti-corrosion performance of the coating. The addition of silane coupling agent KH560 not only improves the dispersibility of the composite filler in the coating, but also enhances the bonding force between the composite filler and the coating matrix and between the coating and the micro-arc oxidation coating, making the coating more firmly attached to the micro-arc oxidation coating and less likely to fall off or crack, thereby improving the long-term anti-corrosion performance of the composite coating.

[0025] Beneficial effects of the present invention:

[0026] (1) Micro-arc oxidation is an innovative surface treatment process for aluminum alloys. It significantly improves the corrosion resistance and surface absorbance of aluminum alloys by constructing a hard oxide layer similar to ceramics. This process is environmentally friendly and meets the requirements of green production. A black micro-arc oxidation coating with a thickness of 6-10 μm and good adhesion to the substrate is prepared on the surface of the aluminum alloy using a specific electrolyte system. This coating not only enhances the corrosion resistance of the aluminum alloy, but also optimizes its surface properties, which is conducive to the close adhesion of the subsequent electrophoretic coating and lays the foundation for the overall performance of the composite coating.

[0027] (2) The composite filler used in the electrophoretic layer was treated with potassium permanganate and hydrogen peroxide to introduce oxygen-containing functional groups into the multi-walled carbon nanotubes, thereby improving the dispersion of the carbon nanotubes in the coating and the bonding strength with the substrate. At the same time, the introduction of zinc as a sacrificial anode further protected the aluminum alloy substrate. The combination of multi-walled carbon nanotubes and graphene oxide formed an intricate network structure, which significantly improved the absorbance, density and hardness of the coating, and effectively blocked the penetration of corrosive media. In addition, the addition of silane coupling agent KH560 not only improved the dispersion of the composite filler in the coating, but also enhanced the bonding strength between the filler and the coating matrix and between the coating and the micro-arc oxidation coating, thereby significantly improving the long-term anti-corrosion performance and overall stability of the composite coating. DETAILED DESCRIPTION

[0028] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0029] In the embodiments of the present invention and the comparative examples:

[0030] Aluminum alloy: purchased from Wuxi Leshan Metal Materials Co., Ltd., grades 6061 and 7075.

[0031] Example 1

[0032] A method for preparing an aluminum alloy corrosion-resistant composite coating, the specific steps of the preparation method are as follows:

[0033] S1-1: The surface of aluminum alloy 6061 was polished with 600# water-abrasive sandpaper, and then the polished aluminum alloy was immersed in an alkaline cleaning solution and ultrasonicated at 60 °C for 10 min. The composition of the alkaline cleaning solution was 25 g / L sodium hydroxide, 45 g / L baking soda, and 1.5 g / L sodium diisooctyl sulfosuccinate. The solvent of the alkaline cleaning solution was deionized water. Then, the aluminum alloy was immersed in a 75% ethanol solution and ultrasonicated for 30 min. Then, the aluminum alloy was dried in a vacuum drying oven at 100 °C for 12 h to obtain the pretreated aluminum alloy.

[0034] S1-2: Sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate and sodium hydroxide are mixed and added into deionized water to prepare micro-arc oxidation solution, wherein the concentration of sodium phosphate is 17.5 g / L, the concentration of sodium silicate is 12.5 g / L, the concentration of sodium fluoride is 12.5 g / L, the concentration of ammonium metavanadate is 7.5 g / L, the concentration of sodium molybdate is 7.5 g / L and the concentration of sodium hydroxide is 7.5 g / L. The pretreated aluminum alloy is placed in the micro-arc oxidation solution at 30 ℃ for micro-arc oxidation treatment, wherein the pretreated aluminum alloy is used as the anode and the stainless steel plate is used as the cathode. Constant current control is adopted during the micro-arc oxidation reaction, and the current density is 3A / dm 2 , the frequency range is 1250 Hz, the duty cycle is 30%, the time is 35 min, after which it is washed with deionized water and dried in a vacuum drying oven at 80 °C for 5 h to obtain a micro-arc oxidation coating with a thickness of 8 μm;

[0035] S1-3: Calculated by mass percentage, 35% aqueous acrylic resin emulsion, 25% aqueous polyurethane emulsion, 10% composite filler, 4% blocked isocyanate, 1.5% polydimethylsiloxane and the remainder deionized water are mixed to prepare an electrophoretic coating, and the aluminum alloy after micro-arc oxidation is placed in an electrophoretic tank for electrophoretic deposition treatment, wherein the cathode material is the aluminum alloy after micro-arc oxidation, and the anode is stainless steel. The electrophoretic deposition is carried out in a DC constant voltage mode, and the temperature of the electrophoretic tank is 30°C. The voltage is controlled to increase to 220 V within 15s, and the deposition time is 2.5 min. After completion, it is washed with deionized water and placed in a 170°C oven for curing for 30 min to obtain the corrosion-resistant composite coating.

[0036] The steps for preparing the composite filler in S1-3 are as follows:

[0037] S7-1: In parts by weight, 10 parts of multi-walled carbon nanotubes were added to 100 parts of deionized water, mixed, and ultrasonicated for 30 minutes, and 4 parts of a mixture of potassium permanganate and hydrogen peroxide were added, wherein the potassium permanganate and hydrogen peroxide in the mixture were mixed in a mass ratio of 1:1, and ultrasonicated for 1.5 hours, and washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A;

[0038] S7-2: 15 parts of powder A were added to 100 parts of deionized water, and ultrasonically dispersed for 30 min. 5 parts of 5 mM zinc nitrate solution were added dropwise at a stirring speed of 650 r / min, and ultrasonicated for 30 min. The pH of the solution was adjusted to 10 with 0.1 M sodium hydroxide, and 15 parts of hydrazine hydrate were added, and ultrasonicated for 10 min. The mixture was transferred to a reactor and heated at 120 °C for 2 h, and then washed with deionized water and anhydrous ethanol, and dried in a -50 °C freeze dryer for 12 h to obtain powder B.

[0039] S7-3: Powder B and graphene oxide were mixed in a mass ratio of 2:1, and the mixture was placed in a ball mill for 1 h at a ball mill speed of 200 r / min. 4 wt% of silane coupling agent KH560 was added, and the ball mill speed was increased to 350 r / min and the mixture was continued for 1 h to obtain the composite filler.

[0040] Example 2

[0041] A method for preparing an aluminum alloy corrosion-resistant composite coating, the specific steps of the preparation method are as follows:

[0042] S1-1: The surface of aluminum alloy 7075 was polished with 600# water-abrasive sandpaper, and then the polished aluminum alloy was immersed in an alkaline cleaning solution and ultrasonicated at 50 °C for 10 min. The composition of the alkaline cleaning solution was 20 g / L sodium hydroxide, 40 g / L baking soda, and 1 g / L sodium diisooctyl sulfosuccinate. The solvent of the alkaline cleaning solution was deionized water. Then, the aluminum alloy was immersed in a 75% ethanol solution and ultrasonicated for 30 min. Then, the aluminum alloy was dried in a vacuum drying oven at 100 °C for 12 h to obtain the pretreated aluminum alloy.

[0043] S1-2: Sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate and sodium hydroxide were mixed and added into deionized water to prepare micro-arc oxidation solution, wherein the concentration of sodium phosphate was 15 g / L, the concentration of sodium silicate was 10 g / L, the concentration of sodium fluoride was 10 g / L, the concentration of ammonium metavanadate was 5 g / L, the concentration of sodium molybdate was 5 g / L and the concentration of sodium hydroxide was 7 g / L. The pretreated aluminum alloy was placed in the micro-arc oxidation solution at 25 ℃ for micro-arc oxidation treatment, wherein the pretreated aluminum alloy was used as the anode and the stainless steel plate was used as the cathode. Constant current control was adopted during the micro-arc oxidation reaction, and the current density was 2.5 A / dm 2 , the frequency range is 1000 Hz, the duty cycle is 25%, the time is 20 min, after which it is washed with deionized water and dried in a vacuum drying oven at 80 °C for 4 h to obtain a micro-arc oxidation coating with a thickness of 6 μm;

[0044] S1-3: 30% aqueous acrylic resin emulsion, 20% aqueous polyurethane emulsion, 5% composite filler, 3% blocked isocyanate, 1% polydimethylsiloxane and the rest deionized water are mixed to prepare electrophoretic coating by mass percentage, and the aluminum alloy after micro-arc oxidation is placed in an electrophoretic tank for electrophoretic deposition treatment, wherein the cathode material is the aluminum alloy after micro-arc oxidation, and the anode is stainless steel. The electrophoretic deposition is carried out in a DC constant voltage mode, and the temperature of the electrophoretic tank is 30°C. The voltage is controlled to increase to 220 V within 15 s, and the deposition time is 2 min. After completion, it is washed with deionized water and placed in a 160°C oven for curing for 20 min to obtain the corrosion-resistant composite coating.

[0045] The steps for preparing the composite filler in S1-3 are as follows:

[0046] S7-1: In parts by weight, 5 parts of multi-walled carbon nanotubes were added to 100 parts of deionized water, mixed, and ultrasonicated for 30 minutes, and 3 parts of a mixture of potassium permanganate and hydrogen peroxide were added, wherein the potassium permanganate and hydrogen peroxide in the mixture were mixed in a mass ratio of 1:1, and ultrasonicated for 1.5 hours, and washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A;

[0047] S7-2: 10 parts of powder A were added to 100 parts of deionized water, and ultrasonically dispersed for 30 min. 5 parts of 5 mM zinc nitrate solution were added dropwise at a stirring speed of 600 r / min, and ultrasonicated for 30 min. The pH of the solution was adjusted to 9.5 with 0.1 M sodium hydroxide, and 10 parts of hydrazine hydrate were added, and ultrasonicated for 10 min. The mixture was transferred to a reactor and heated at 120 °C for 2 h, and then washed with deionized water and anhydrous ethanol, and dried in a -50 °C freeze dryer for 12 h to obtain powder B.

[0048] S7-3: Powder B and graphene oxide were mixed in a mass ratio of 1:1, and the mixture was ball-milled in a ball mill for 1 h at a speed of 150 r / min. 3 wt% of silane coupling agent KH560 was added, and the ball mill speed was increased to 300 r / min and the mixture was ball-milled for 1 h to obtain the composite filler.

[0049] Example 3

[0050] A method for preparing an aluminum alloy corrosion-resistant composite coating, the specific steps of the preparation method are as follows:

[0051] S1-1: The surface of aluminum alloy 6061 was polished with 600# water-abrasive sandpaper, and then the polished aluminum alloy was immersed in an alkaline cleaning solution and ultrasonicated at 70 °C for 10 min. The composition of the alkaline cleaning solution was 30 g / L sodium hydroxide, 50 g / L baking soda, and 2 g / L sodium diisooctyl sulfosuccinate. The solvent of the alkaline cleaning solution was deionized water. Then, the aluminum alloy was immersed in a 75% ethanol solution and ultrasonicated for 30 min. Then, the aluminum alloy was dried in a vacuum drying oven at 100 °C for 12 h to obtain the pretreated aluminum alloy.

[0052] S1-2: Sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate and sodium hydroxide were mixed and added into deionized water to prepare micro-arc oxidation solution, wherein the concentration of sodium phosphate was 20 g / L, the concentration of sodium silicate was 15 g / L, the concentration of sodium fluoride was 15 g / L, the concentration of ammonium metavanadate was 10 g / L, the concentration of sodium molybdate was 10 g / L and the concentration of sodium hydroxide was 8 g / L. The pretreated aluminum alloy was placed in the micro-arc oxidation solution at 35 ℃ for micro-arc oxidation treatment, wherein the pretreated aluminum alloy was used as the anode and the stainless steel plate was used as the cathode. Constant current control was adopted during the micro-arc oxidation reaction, and the current density was 3.5 A / dm 2 , the frequency range is 1500 Hz, the duty cycle is 35%, the time is 50 min, after which it is washed with deionized water and dried in a vacuum drying oven at 80 °C for 6 h to obtain a micro-arc oxidation coating with a thickness of 10 μm;

[0053] S1-3: 40% aqueous acrylic resin emulsion, 30% aqueous polyurethane emulsion, 15% composite filler, 5% blocked isocyanate, 2% polydimethylsiloxane and the remainder deionized water are mixed to prepare electrophoretic coating by mass percentage, and the aluminum alloy after micro-arc oxidation is placed in an electrophoretic tank for electrophoretic deposition treatment, wherein the cathode material is the aluminum alloy after micro-arc oxidation, and the anode is stainless steel. The electrophoretic deposition is carried out in a DC constant voltage mode, and the temperature of the electrophoretic tank is 30°C. The voltage is controlled to increase to 220 V within 15s, and the deposition time is 3 min. After completion, it is washed with deionized water and placed in an oven at 180°C for curing for 40 min to obtain the corrosion-resistant composite coating.

[0054] The steps for preparing the composite filler in S1-3 are as follows:

[0055] S7-1: In parts by weight, 15 parts of multi-walled carbon nanotubes were added to 100 parts of deionized water, mixed, and ultrasonicated for 30 minutes, and 5 parts of a mixture of potassium permanganate and hydrogen peroxide were added, wherein the potassium permanganate and hydrogen peroxide in the mixture were mixed in a mass ratio of 1:1, and ultrasonicated for 1.5 hours, and washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A;

[0056] S7-2: 20 parts of powder A were added to 100 parts of deionized water, ultrasonically dispersed for 30 min, 5 parts of 5 mM zinc nitrate solution were added dropwise at a stirring speed of 700 r / min, ultrasonicated for 30 min, the pH of the solution was adjusted to 10.5 with 0.1 M sodium hydroxide, 20 parts of hydrazine hydrate were added, ultrasonicated for 10 min, transferred to a reactor and heated at 120 °C for 2 h, then washed with deionized water and anhydrous ethanol, and dried in a -50 °C freeze dryer for 12 h to obtain powder B;

[0057] S7-3: Powder B and graphene oxide were mixed in a mass ratio of 3:1, and the mixture was ball-milled in a ball mill for 1 h at a speed of 250 r / min. 5 wt% of silane coupling agent KH560 was added, and the ball mill speed was increased to 400 r / min and the mixture was ball-milled for 1 h to obtain the composite filler.

[0058] Comparative Example 1

[0059] No zinc nitrate was added during the preparation of the composite filler, and the remaining steps were the same as those in Example 1.

[0060] Comparative Example 2

[0061] No graphene oxide is added in the preparation of the composite filler, and the remaining steps are consistent with Example 1.

[0062] Comparative Example 3

[0063] S1-2 treatment is not performed, and the remaining steps are consistent with Example 1.

[0064] Comparative Example 4

[0065] S1-3 treatment is not performed, and the remaining steps are consistent with Example 1.

[0066] The appearance colors of the embodiments and comparative examples were tested under D65 standard light source.

[0067] The corrosion resistance of the embodiments and comparative examples was tested in accordance with GB / T 10125-2021. The concentration of 5% sodium chloride was adjusted with glacial acetic acid to make the pH value of the solution 3 to prepare a spray medium. The test temperature was 35 °C. After continuous spraying for 240 h, the corrosion of the samples was observed.

[0068] The experimental results are summarized in the following table:

[0069]

[0070] It can be seen from the examples and comparative example data that the corrosion-resistant composite coating prepared by the present invention enables the aluminum alloy to have high light absorption performance and excellent corrosion resistance.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an aluminum alloy corrosion-resistant composite coating, characterized in that: The specific steps of the preparation method are as follows: S1-1: The aluminum alloy surface was polished with 600# water-abrasive sandpaper, and then the polished aluminum alloy was immersed in an alkaline cleaning solution and ultrasonicated at 50-70 °C for 10 min, then immersed in a 75% mass fraction ethanol solution and ultrasonicated for 30 min, and then dried in a vacuum drying oven at 100 °C for 12 h to obtain the pretreated aluminum alloy; S1-2: Sodium phosphate, sodium silicate, sodium fluoride, ammonium metavanadate, sodium molybdate and sodium hydroxide are mixed and added into deionized water to prepare a micro-arc oxidation solution, and the pretreated aluminum alloy is placed in the micro-arc oxidation solution at 25-35 ℃ for micro-arc oxidation treatment, wherein the pretreated aluminum alloy is used as the anode and the stainless steel plate is used as the cathode. After the treatment, the aluminum alloy is washed with deionized water and dried in a vacuum drying oven at 80 ℃ for 4-6 hours to obtain a micro-arc oxidation coating; S1-3: A water-based acrylic resin emulsion, a water-based polyurethane emulsion, a composite filler, a blocked isocyanate, polydimethylsiloxane and deionized water are mixed to prepare an electrophoretic coating, and the aluminum alloy after micro-arc oxidation is placed in an electrophoretic tank for electrophoretic deposition treatment, wherein the cathode material is the aluminum alloy after micro-arc oxidation, and the anode is stainless steel. After the treatment, the aluminum alloy is washed with deionized water and placed in an oven at 160-180°C for curing for 20-40 min to obtain the corrosion-resistant composite coating; The steps of preparing the composite filler are as follows: S7-1: In parts by weight, 5-15 parts of multi-walled carbon nanotubes were added to 100 parts of deionized water, mixed, and ultrasonicated for 30 min, and 3-5 parts of a mixture of potassium permanganate and hydrogen peroxide were added, ultrasonicated for 1.5 h, washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60 °C for 12 h to obtain powder A; S7-2: 10-20 parts of powder A were added to 100 parts of deionized water, ultrasonically dispersed for 30 min, 5 parts of 5 mM zinc nitrate solution were added dropwise at a stirring speed of 600-700 r / min, ultrasonicated for 30 min, the pH of the solution was adjusted to 9.5-10.5 with 0.1 M sodium hydroxide, 10-20 parts of hydrazine hydrate were added, ultrasonicated for 10 min, transferred to a reactor and heated at 120 °C for 2 h, then washed with deionized water and anhydrous ethanol, and dried in a -50 °C freeze dryer for 12 h to obtain powder B; S7-3: Powder B and graphene oxide were mixed and placed in a ball mill for ball milling for 1 h at a ball milling speed of 150-250 r / min, 3-5 wt% of silane coupling agent KH560 was added, the ball milling speed was increased to 300-400 r / min and the ball milling was continued for 1 h to obtain the composite filler.

2. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: The composition of the alkaline washing solution in S1-1 is 20-30 g / L sodium hydroxide, 40-50 g / L baking soda, and 1-2 g / L sodium diisooctyl sulfosuccinate, and the solvent of the alkaline washing solution is deionized water.

3. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: The concentrations of the components in the micro-arc oxidation solution in S1-2 are 15-20 g / L sodium phosphate, 10-15 g / L sodium silicate, 10-15 g / L sodium fluoride, 5-10 g / L ammonium metavanadate, 5-10 g / L sodium molybdate, and 7-8 g / L sodium hydroxide.

4. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: In the micro-arc oxidation reaction process in S1-2, a constant current control method is adopted, and the current density is 2.5~3.5 A / dm 2 , the frequency range is 1000~1500 Hz, the duty cycle is 25~35%, and the time is 20~50 min.

5. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: The thickness of the micro-arc oxidation coating in S1-2 is 6-10 μm.

6. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: The mass proportions of the components in the electrophoretic coating in S1-3 are 30% to 40% of water-based acrylic resin emulsion, 20% to 30% of water-based polyurethane emulsion, 5% to 15% of composite filler, 3% to 5% of blocked isocyanate, 1% to 2% of polydimethylsiloxane, and the balance of deionized water.

7. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: The electrophoretic deposition in S1-3 is carried out in a DC constant voltage mode, the temperature of the electrophoretic tank is 30±0.5°C, the voltage is controlled to increase to 220 V within 15 s, and the deposition time is 2~3 min.

8. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: In the S7-1, potassium permanganate and hydrogen peroxide are mixed in a mass ratio of 1:

1.

9. The method for preparing an aluminum alloy corrosion-resistant composite coating according to claim 1, characterized in that: In the S7-3, powder B and graphene oxide are mixed in a mass ratio of (1-3):1.

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