Aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating and preparation method

Abstract

The invention discloses an aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating and a preparation method. The aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating comprises an inner layer and an outer layer, the inner layer is a corrosion-resistant ceramic layer containing niobium pentoxide, and the outer layer is an FEVE fluorocarbon resin organic layer modified by rare earth lanthanum or / and holmium containing silver-copper alloy powder. According to the method, the aluminum alloy long-acting integrated multifunctional protective layer with a compact and uniform surface microstructure structure can be obtained, good corrosion resistance, mildew resistance and antifouling performance are achieved, and the problems of biological fouling and multi-factor synergistic corrosion faced by aluminum alloy materials in the marine environment can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the field of aluminum alloy surface treatment technology and new corrosion-resistant and antifouling materials in harsh marine environments, and specifically relates to a micro-arc oxidation-rare earth modified FEVE composite coating on the surface of an aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum alloy, a metal material with an excellent strength-to-weight ratio, is widely used in marine engineering applications such as ships, offshore platforms, and offshore facilities due to its excellent mechanical properties and corrosion resistance. However, the unique characteristics of the marine environment, such as high salinity, strong UV radiation, humid climates, and complex microbial communities, pose significant challenges to the durability of aluminum alloys. Chloride ions in seawater can penetrate the aluminum alloy's oxide film and destroy its density, leading to corrosion phenomena such as pitting and crevice corrosion. Furthermore, organic matter, sediment, and the adhesion of microorganisms in the marine environment exacerbate fouling on the aluminum alloy surface and may even lead to the growth of mold, further compromising its performance. Surface corrosion not only reduces the metal's strength but can also cause stress corrosion cracking, threatening the integrity and safety of the structure. Furthermore, the presence of fouling and mold not only degrades the aluminum alloy's surface aesthetics but can also accelerate aging and reduce its resistance to environmental degradation. Therefore, to ensure the long-term stability and safety of marine engineering equipment, effective anti-corrosion, anti-fouling, and anti-mold treatments are essential for aluminum alloys. These treatments not only improve the corrosion resistance of the aluminum alloy surface and extend its service life, but also effectively inhibit the growth of dirt and mold, ensuring the reliability of the aluminum alloy in extreme marine environments.

[0003] At present, the anti-corrosion coatings widely used in the marine field include zinc-based, copper-based and other metal coatings and polymer coatings, which have achieved certain success in preventing seawater corrosion. However, the prevention and control effects of these coatings on biological fouling are relatively poor, and many traditional antifouling agents (such as copper-based coatings, zinc-based coatings, chlorides, etc.) have major environmental pollution problems. Although copper-based antifouling agents can effectively prevent the attachment of algae and shellfish, they are highly toxic to the marine ecosystem. Long-term use may cause water pollution, affect the growth of aquatic organisms, and even destroy the ecological balance. Over time, the effects of these traditional antifouling agents will gradually weaken, especially in high-salinity and high-temperature marine environments. The emergence of resistant organisms has caused these traditional antifouling materials to face a continuous decline in effectiveness. Therefore, there is an urgent need to develop a more environmentally friendly, long-lasting and efficient antifouling coating material to cope with the problems of corrosion and biological fouling in the marine environment. Summary of the Invention

[0004] In order to overcome the above problems existing in the prior art, the present invention proposes an integrated micro-arc oxidation-rare earth modified FEVE composite coating with corrosion resistance, mildew resistance and anti-fouling properties on the surface of aluminum alloy and a preparation method thereof.

[0005] The first object of the present invention is to provide a micro-arc oxidation-rare earth modified FEVE composite coating on the surface of an aluminum alloy, which includes an inner layer and an outer layer, wherein the inner layer is a corrosion-resistant ceramic layer containing niobium pentoxide, and the outer layer is a FEVE fluorocarbon resin organic layer modified with rare earth lanthanum or / and holmium containing silver-copper alloy powder.

[0006] Preferably, the inner layer has a thickness of 3-5 μm, and the outer layer has a thickness of 50±5 μm.

[0007] Preferably, the inner layer is prepared by a micro-arc oxidation process, and the outer layer is prepared by spraying.

[0008] A second object of the present invention is to provide a method for preparing the above-mentioned micro-arc oxidation-rare earth modified FEVE composite coating on the surface of an aluminum alloy, which comprises the following steps:

[0009] Step 1: Clean and dry the aluminum alloy surface, and prepare a micro-arc oxidation electrolyte containing niobium pentoxide;

[0010] Step 2: placing the cleaned aluminum alloy into the micro-arc oxidation electrolyte prepared in step 1, mechanically stirring the micro-arc oxidation electrolyte, and maintaining the electrolyte temperature at 15° C.-20° C. to perform micro-arc oxidation to obtain an inner layer;

[0011] Step 3, preparing an anhydrous ethanol-KH550 aqueous solution to perform interface transition treatment on the aluminum alloy micro-arc oxidation coating: soaking the aluminum alloy micro-arc oxidation coating obtained in step 2 in an anhydrous ethanol-KH550 solution for 10-30 minutes, taking it out and drying it, and then heat treating it at 100-150° C. for 30-60 minutes to enhance the interface bonding strength of the coating surface;

[0012] Step 4, drying the aluminum alloy obtained in step 3;

[0013] Step 5: preparing an organic slurry containing nano silver-copper alloy powder and a FEVE fluorocarbon resin modified with rare earth lanthanum and / or holmium, spraying the organic slurry onto the surface of the aluminum alloy obtained in step 4 that has been subjected to micro-arc oxidation to form an inner layer, and drying the aluminum alloy coated with the organic modified coating;

[0014] The micro-arc oxidation electrolyte includes: 9-11g / L sodium hexametaphosphate, 7-9g / L sodium silicate, 3-5g / L sodium hydroxide, and 5-7g / L niobium pentoxide; the organic slurry includes: by mass percentage, 5-7% nano silver copper alloy powder, 0-10% lanthanum nitrate, 0-10% holmium nitrate, 5-7% biuret, 11-13% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; the anhydrous ethanol-KH550 aqueous solution includes: by mass percentage, 75-85% anhydrous ethanol, 1-3% KH550, and the balance is water.

[0015] Preferably, the components and mass percentages of the organic slurry are: 6% nano silver copper alloy powder, 10% lanthanum nitrate, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; or, 6% nano silver copper alloy powder, 10% lanthanum nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; or, 6% nano silver copper alloy powder, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; the mass ratio of the FEVE fluorocarbon resin to xylene is 2:1.

[0016] Preferably, the micro-arc oxidation electrolyte comprises: 10 g / L sodium hexametaphosphate, 8 g / L sodium silicate, 4 g / L sodium hydroxide, and 6 g / L niobium pentoxide.

[0017] Preferably, the specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: anhydrous ethanol 80%, pure water 18%, and KH550 2%.

[0018] Preferably, the particle size of the nano silver copper alloy powder is 100-800 mesh, the mass ratio of Ag to Cu is 1:4, the cleaning and drying of the aluminum alloy surface is to clean the aluminum alloy surface with deionized water and anhydrous ethanol, and blow dry it with a hair dryer; the step 4 is to place the aluminum alloy obtained in step 3 into a drying oven, dry it at 60°C for 45 minutes, and dry it at 120°C for 60 minutes; the drying of the aluminum alloy coated with the organic modified coating is to place the aluminum alloy coated with the organic modified coating into a drying oven, and dry it at 30-40°C for 24 hours; the aluminum alloy is 5056 aluminum alloy.

[0019] The third object of the present invention is to provide the application of the above-mentioned aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating in anti-aflatoxin.

[0020] The fourth object of the present invention is to provide the application of the above-mentioned aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating in anti-diatom applications.

[0021] The present invention first prepares a 3-5 μm porous oxide ceramic layer on the surface of an aluminum alloy using micro-arc oxidation technology. By adding a high content of 6g / L niobium pentoxide to the electrolyte, the ceramic layer is given good corrosion resistance. The aluminum alloy micro-arc oxidation coating is subjected to an interface transition treatment. The aluminum alloy with the micro-arc oxidation coating is immersed in an anhydrous ethanol-KH550 aqueous solution to enhance the interfacial bonding between the micro-arc oxidation coating and the organic coating. A fluorocarbon resin slurry containing nano-silver-copper alloy powder and FEVE modified with rare earth lanthanum and holmium is prepared, wherein the mass percentage of nano-silver-copper alloy powder is 6%, the mass percentage of lanthanum nitrate is 10%, and the mass percentage of holmium nitrate is 10%. The prepared slurry is sprayed onto the surface of the micro-arc oxidation coating of the aluminum alloy after the interface transition treatment using a spray gun, with a spraying thickness of 50±5μm. The prepared integrated coating has a uniform, dense, and relatively smooth surface, completely covering the surface of the 5056 aluminum alloy. The corrosion resistance of the magnesium alloy surface is greatly improved, the electrochemical corrosion potential moves significantly in the positive direction, and the self-corrosion current density is greatly reduced, showing excellent anti-fungal and anti-biofouling properties.

[0022] The beneficial effect of the present invention is that the present invention can obtain a long-lasting integrated multifunctional protective layer of aluminum alloy with a dense and uniform surface microstructure, which has good corrosion resistance, mildew resistance and anti-fouling properties, and can effectively solve the problems of biological fouling and multi-factor synergistic corrosion faced by aluminum alloy materials in marine environments.

[0023] The process flow of the present invention is simple and easy to operate. The coating formed on the surface of the aluminum alloy has excellent corrosion resistance and is multifunctional in anti-mildew and anti-fouling. It has significant application value and can meet the actual needs of aluminum alloy materials for efficient anti-corrosion, anti-fouling and anti-mildew in harsh marine environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Comparison of the electrochemical open circuit potentials of the 5056 aluminum alloy substrate and the rare earth lanthanum modified organic coating prepared in Example 1 of the present invention.

[0025] Figure 2 Comparison of electrochemical impedance values ​​between the 5056 aluminum alloy substrate and the rare earth lanthanum modified organic coating prepared in Example 1 of the present invention.

[0026] Figure 3 Comparison of electrochemical polarization curves of the 5056 aluminum alloy substrate and the rare earth lanthanum modified organic coating prepared in Example 1 of the present invention.

[0027] Figure 4 This is a comparison of the anti-mildew test between the 5056 aluminum alloy substrate prepared in Example 1 of the present invention and the rare earth lanthanum modified organic coating.

[0028] Figure 5This is a comparison of the diatom resistance test between the 5056 aluminum alloy substrate prepared in Example 1 of the present invention and the rare earth lanthanum modified organic coating.

[0029] Figure 6 Comparison of the electrochemical open circuit potentials of the 5056 aluminum alloy substrate and the rare earth holmium modified organic coating prepared in Example 2 of the present invention.

[0030] Figure 7 Comparison of electrochemical impedance values ​​between the 5056 aluminum alloy substrate and the rare earth holmium modified organic coating prepared in Example 2 of the present invention.

[0031] Figure 8 Comparison of electrochemical polarization curves of the 5056 aluminum alloy substrate and the rare earth holmium modified organic coating prepared in Example 2 of the present invention.

[0032] Figure 9 This is a comparison of the anti-fungal test between the 5056 aluminum alloy substrate prepared in Example 2 of the present invention and the rare earth holmium modified organic coating.

[0033] Figure 10 This is a comparison of the diatom resistance test between the 5056 aluminum alloy substrate prepared in Example 2 of the present invention and the rare earth holmium modified organic coating.

[0034] Figure 11 Comparison of the electrochemical open circuit potentials of the 5056 aluminum alloy substrate and the rare earth lanthanum and holmium modified organic coating prepared in Example 3 of the present invention.

[0035] Figure 12 Comparison of electrochemical impedance values ​​between the 5056 aluminum alloy substrate and the rare earth lanthanum and holmium modified organic coating prepared in Example 3 of the present invention.

[0036] Figure 13 Comparison of electrochemical polarization curves of the 5056 aluminum alloy substrate and the rare earth lanthanum and holmium modified organic coating prepared in Example 3 of the present invention.

[0037] Figure 14 This is a comparison of the anti-fungal test between the 5056 aluminum alloy substrate prepared in Example 3 of the present invention and the rare earth lanthanum and holmium modified organic coating.

[0038] Figure 15 This is a comparison of the diatom resistance test between the 5056 aluminum alloy substrate prepared in Example 3 of the present invention and the rare earth lanthanum and holmium modified organic coating. DETAILED DESCRIPTION

[0039] The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] This embodiment discloses an integrated micro-arc oxidation-rare earth-modified FEVE composite coating for aluminum alloy surfaces that provides corrosion resistance, mildew resistance, and stain resistance. The coating comprises an inner layer and an outer layer. The inner layer is a corrosion-resistant ceramic layer containing niobium pentoxide, and the outer layer is a FEVE fluorocarbon resin organic layer modified with rare earth elements lanthanum and holmium containing silver-copper alloy powder. The inner layer has a thickness of 3-5 μm, and the outer layer has a thickness of 50 ± 5 μm. The inner layer is prepared by micro-arc oxidation, and the outer layer is spray-coated.

[0042] A method for preparing an integrated micro-arc oxidation-rare earth modified FEVE composite coating for aluminum alloy surface with corrosion resistance, mildew resistance and antifouling properties, specifically comprising:

[0043] Step 1: Clean the surface of the aluminum alloy with deionized water and anhydrous ethanol, dry it with a hair dryer, and prepare a micro-arc oxidation electrolyte containing niobium pentoxide;

[0044] The micro-arc oxidation electrolyte includes: 10g / L sodium hexametaphosphate, 8g / L sodium silicate, 4g / L sodium hydroxide, 6g / L niobium pentoxide, and the balance is water.

[0045] Step 2: Place the cleaned aluminum alloy into the micro-arc oxidation electrolyte prepared in step 1 and mechanically stir the micro-arc oxidation electrolyte at a stirring speed of 30-50 rpm / min until the micro-arc oxidation process is complete. Maintain the electrolyte temperature at 15°C-20°C to micro-arc oxidation to obtain the inner layer.

[0046] Step 3: Prepare an anhydrous ethanol-KH550 aqueous solution and perform interface transition treatment on the aluminum alloy micro-arc oxidation coating. Immerse the aluminum alloy micro-arc oxidation coating obtained in step 2 in an anhydrous ethanol-KH550 solution for 10-30 minutes to form a transition layer. Then take out the workpiece and dry it in air or in an oven (40-60°C) for 45 minutes to ensure that the surface is completely dry. Further heat treatment (baking at 100-150°C for 30-60 minutes) is performed to enhance the interfacial bonding strength. The specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: 80% anhydrous ethanol, 18% pure water, and 2% KH550 (the Chinese name of KH550 solution is aminosilane solution, where KH550 is the abbreviation of γ-aminopropyltriethoxysilane).

[0047] Step 4: Place the aluminum alloy obtained in step 3 into a drying oven and dry it at 60° C. for 45 min and then at 120° C. for 60 min.

[0048] In step 5, an organic slurry containing nano-silver-copper alloy powder and a FEVE fluorocarbon resin modified with rare earth elements lanthanum and / or holmium is prepared and sprayed onto the surface of the aluminum alloy, which has been subjected to micro-arc oxidation to form an inner layer, obtained in step 4. The modified organic slurry comprises the following components by weight: 6% nano-silver-copper alloy powder, 10% lanthanum nitrate and / or 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the remainder FEVE fluorocarbon resin and xylene, with the weight ratio of FEVE fluorocarbon resin to xylene being 2:1. The nano-silver-copper alloy powder has a particle size of 100-800 mesh, and the weight ratio of Ag to Cu is 1:4.

[0049] Step 6: Place the aluminum alloy obtained in step 5 into a drying oven and dry at 30-40°C for 24 hours.

[0050] Example 1:

[0051] Step 1: Clean the surface of 5056 aluminum alloy with deionized water and anhydrous ethanol, then dry it with a hair dryer. Prepare a micro-arc oxidation electrolyte containing niobium pentoxide. The electrolyte formula is: 10g / L sodium hexametaphosphate, 8g / L sodium silicate, 4g / L sodium hydroxide, 6g / L niobium pentoxide, and the balance is water.

[0052] Step 2: Prepare a micro-arc oxidation (MAO) corrosion-resistant coating on the surface of the 5056 aluminum alloy. Place the cleaned aluminum alloy in the MAO electrolyte prepared in Step 1. Mechanically stir the MAO electrolyte at 30 rpm / min until the MAO process is complete. Maintain the electrolyte temperature at 15°C and MAO to obtain the inner layer.

[0053] Step 3: Prepare an anhydrous ethanol-KH550 aqueous solution and perform interface transition treatment on the aluminum alloy micro-arc oxidation coating. Immerse the aluminum alloy micro-arc oxidation coating obtained in step 2 in an anhydrous ethanol-KH550 solution for 10 minutes to form a transition layer. Then take out the workpiece and dry it in air or in an oven at 40°C for 45 minutes to ensure that the surface is completely dry. Further heat treatment (baking at 100°C for 30 minutes) is performed to enhance the interfacial bonding strength. The specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: 80% anhydrous ethanol, 18% pure water, and 2% KH550.

[0054] Step 4: Place the aluminum alloy obtained in step 3 into a drying oven and dry it at 60° C. for 45 min and then at 120° C. for 60 min.

[0055] Step 5, prepare an organic slurry containing nano silver copper alloy powder and FEVE fluorocarbon resin modified with rare earth lanthanum, and spray the organic slurry onto the surface of the aluminum alloy obtained in step 4 that has been subjected to micro-arc oxidation treatment to form an inner layer. The components and mass percentages of the modified organic slurry are: 6% nano silver copper alloy powder, 10% lanthanum nitrate, 6% biuret, 12% anhydrous ethanol, and the remainder are FEVE fluorocarbon resin and xylene, and the mass ratio of the FEVE fluorocarbon resin to xylene is 2:1. The spraying thickness is 50±5μm, the particle size of the nano silver copper alloy powder is 100-800 mesh, and the mass ratio of Ag to Cu is 1:4. The aluminum alloy coated with the organic modified coating is placed in a drying oven and dried at 30-40°C for 24 hours.

[0056] The prepared integrated coating has a uniform, dense and relatively smooth surface, completely covering the surface of the 5056 aluminum alloy.

[0057] Step 6: Electrochemical testing of the aluminum alloy composite coating and aluminum alloy substrate obtained in step 5 was performed using a PARSTAT 4000A electrochemical workstation, a platinum sheet as the auxiliary electrode, a saturated calomel electrode (SCE) as the reference electrode, and a three-electrode system. The corrosion performance of the 5056 aluminum alloy substrate and the aluminum alloy composite coating samples in natural seawater was studied using open circuit potential (OCP) measurement, potentiodynamic polarization test, and electrochemical impedance spectroscopy (EIS) to evaluate the corrosion behavior of the samples in natural seawater. The 5056 aluminum alloy substrate and the aluminum alloy composite coating were subjected to an OCP test for 1200 s at a scan rate of 2 mV·s. -1 The corrosion potential (E corr ) and corrosion current density (i corr The samples were immersed in a natural seawater solution for 20 minutes to stabilize the open-circuit potential. A sinusoidal alternating current (AC) with an amplitude of 10 mV was applied to the 5056 aluminum alloy substrate and 100 mV to the 5056 aluminum alloy composite coating within a frequency range of 10 mHz to 100 kHz.

[0058] from Figure 1 、 Figure 2 、 Figure 3 It can be seen that the corrosion resistance of the 5056 aluminum alloy surface is greatly improved, the electrochemical corrosion potential moves significantly in the positive direction, and the self-corrosion current density is greatly reduced.

[0059] In step 7, the aluminum alloy composite coating and the aluminum alloy substrate obtained in step 5 were subjected to a flavus resistance test. The 5056 aluminum alloy composite coating and the substrate were subjected to a mildew resistance test according to the Petri dish method specified in section 7.4.1 of GB / T 1741-2020, "Test Method for Mildew Resistance of Paint Films." The test conditions were: 14 days, 90% relative humidity, and 28°C.

[0060] like Figure 4 As shown in the figure, after the anti-aflatoxin test in the laboratory, the mold growth on the coating surface was significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent anti-fungal performance.

[0061] Step 8, the aluminum alloy composite coating obtained in step 5 and the aluminum alloy substrate are subjected to an anti-diatom test, and the anti-algae adhesion performance of the coating is studied with Crescent Nitzschia as the research object. The specific test method is as follows: the diatom liquid (Binzhou Fengyun Biotechnology Co., Ltd., Crescent Nitzschia species) is placed in a sterilized conical flask, sealed with an oxygen-based bottom film, and then placed in a light incubator for activation and expansion. The light intensity is set to 3000 lux, the light and dark cycle is 12 / 12h, the temperature is 21±2℃, and the conical flask is shaken 1 to 3 times a day during the culture process. When the number of diatoms reaches 1×10 5 When the diatom solution reached a concentration of 1000 diatoms / mL, the diatom solution was aliquoted, with 500 mL added to each conical flask. The aluminum alloy composite coating (20 mm x 30 mm x 5 mm) and the aluminum alloy substrate (20 mm x 30 mm x 5 mm) were then placed on the flask for antifouling performance testing. The incubation conditions were: light intensity of 3000 lux, a 12 / 12 h light / dark cycle, and a temperature of 21 ± 2°C. The conical flasks were shaken 1–3 times daily during the incubation period. The coatings were removed from the diatom solution at various time intervals and the surface was gently rinsed with PBS buffer. After diatom attachment, the number of attached diatoms was observed under a fluorescence microscope.

[0062] like Figure 5 As shown in the figure, after the laboratory anti-diatom test, the diatom attachment on the coating surface was significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent anti-biofouling performance.

[0063] Example 2:

[0064] Step 1: Clean the surface of 5056 aluminum alloy with deionized water and anhydrous ethanol, then dry it with a hair dryer. Prepare a micro-arc oxidation electrolyte containing niobium pentoxide. The electrolyte formula is: 10g / L sodium hexametaphosphate, 8g / L sodium silicate, 4g / L sodium hydroxide, 6g / L niobium pentoxide, and the balance is water.

[0065] Step 2: Prepare a micro-arc oxidation (MAO) corrosion-resistant coating on the surface of the 5056 aluminum alloy. Place the cleaned aluminum alloy in the MAO electrolyte prepared in Step 1. Mechanically stir the MAO electrolyte at 40 rpm until the MAO process is complete. Maintain the electrolyte temperature at 17°C and MAO to obtain the inner layer.

[0066] Step 3, prepare anhydrous ethanol-KH550 aqueous solution, perform interface transition treatment on the aluminum alloy micro-arc oxidation coating, and soak the aluminum alloy micro-arc oxidation coating obtained in step 2 in anhydrous ethanol-KH550 solution for 20 minutes to form a transition layer. Then take out the workpiece and dry it in air or in an oven (50°C) for 45 minutes to ensure that the surface is completely dry. Further heat treatment (baking at 125°C for 45 minutes) is performed to enhance the interfacial bonding strength. The specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: 80% anhydrous ethanol, 18% pure water, and 2% KH550.

[0067] Step 4: Place the aluminum alloy obtained in step 3 into a drying oven and dry it at 60° C. for 45 min and then at 120° C. for 60 min.

[0068] Step 5, prepare an organic slurry containing nano silver copper alloy powder and FEVE fluorocarbon resin modified with rare earth holmium, and spray the organic slurry onto the surface of the aluminum alloy obtained in step 4 that has been subjected to micro-arc oxidation treatment to form an inner layer. The components and mass percentages of the modified organic slurry are: 6% nano silver copper alloy powder, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the remainder are FEVE fluorocarbon resin and xylene, and the mass ratio of the FEVE fluorocarbon resin to xylene is 2:1. The spraying thickness is 50±5μm, the particle size of the nano silver copper alloy powder is 100-800 mesh, and the mass ratio of Ag to Cu is 1:4. The aluminum alloy coated with the organic modified coating is placed in a drying oven and dried at 30-40°C for 24 hours.

[0069] The prepared integrated coating has a uniform, dense and relatively smooth surface, completely covering the surface of the 5056 aluminum alloy.

[0070] Step 6: Electrochemical testing of the aluminum alloy composite coating and aluminum alloy substrate obtained in step 5 was performed using a PARSTAT 4000A electrochemical workstation, a platinum sheet as the auxiliary electrode, a saturated calomel electrode (SCE) as the reference electrode, and a three-electrode system. The corrosion performance of the 5056 aluminum alloy substrate and the aluminum alloy composite coating samples in natural seawater was studied by open circuit potential (OCP) measurement, potentiodynamic polarization test, and electrochemical impedance spectroscopy (EIS) to evaluate the corrosion behavior of the samples in natural seawater. The 5056 aluminum alloy substrate and the aluminum alloy composite coating were subjected to an OCP test for 1200s with a scan rate of 2mV·s -1 The corrosion potential (E corr ) and corrosion current density (i corrThe samples were immersed in a natural seawater solution for 20 minutes to stabilize the open-circuit potential. A sinusoidal alternating current (AC) with an amplitude of 10 mV was applied to the 5056 aluminum alloy substrate and a 100 mV AC was applied to the 5056 aluminum alloy composite coating within a frequency range of 10 mHz to 100 kHz.

[0071] from Figure 6 、 Figure 7 、 Figure 8 It can be seen that the corrosion resistance of the magnesium alloy surface is greatly improved, the electrochemical corrosion potential moves significantly in the positive direction, and the self-corrosion current density is greatly reduced.

[0072] In step 7, the aluminum alloy composite coating and the aluminum alloy substrate obtained in step 5 were subjected to a flavus resistance test. The 5056 aluminum alloy composite coating and the substrate were subjected to a mildew resistance test according to the Petri dish method specified in section 7.4.1 of GB / T 1741-2020, "Test Method for Mildew Resistance of Paint Films." The test conditions were: 14 days, 90% relative humidity, and 28°C.

[0073] like Figure 9 As shown in the figure, after the anti-aflatoxin test in the laboratory, the mold growth on the coating surface was significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent anti-fungal performance.

[0074] Step 8: Conduct an anti-diatom test on the aluminum alloy composite coating and the aluminum alloy substrate obtained in step 5. Take the crescent-shaped algae as the research object to study the anti-algae adhesion performance of the coating. The specific test method is as follows: Place the diatom liquid in a sterilized conical flask, seal it with an oxygen-based bottom film, and then place it in a light incubator for activation and expansion. The light intensity is set to 3000 lux, the light and dark cycle is 12 / 12h, the temperature is 21±2℃, and the conical flask is shaken 1 to 3 times a day during the culture process. When the number of diatoms reaches 1×10 5 When the diatom solution reached a concentration of 1000 diatoms / mL, the diatom solution was aliquoted, with 500 mL added to each conical flask. The aluminum alloy composite coating (20 mm x 30 mm x 5 mm) and the aluminum alloy substrate (20 mm x 30 mm x 5 mm) were then placed on the flask for antifouling performance testing. The incubation conditions were: light intensity of 3000 lux, a 12 / 12 h light / dark cycle, and a temperature of 21 ± 2°C. The conical flasks were shaken 1–3 times daily during the incubation period. The coatings were removed from the diatom solution at various time intervals and the surface was gently rinsed with PBS buffer. After diatom attachment, the number of attached diatoms was observed under a fluorescence microscope.

[0075] like Figure 10 As shown in the figure, after the anti-diatom experiment in the laboratory, the diatom attachment on the coating surface was significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent anti-biofouling performance.

[0076] Example 3:

[0077] Step 1: Clean the surface of 5056 aluminum alloy with deionized water and anhydrous ethanol, then dry it with a hair dryer. Prepare a micro-arc oxidation electrolyte containing niobium pentoxide. The electrolyte formula is: 10g / L sodium hexametaphosphate, 8g / L sodium silicate, 4g / L sodium hydroxide, 6g / L niobium pentoxide, and the balance is water.

[0078] Step 2: Prepare a micro-arc oxidation (MAO) corrosion-resistant coating on the surface of the 5056 aluminum alloy. Place the cleaned aluminum alloy in the MAO electrolyte prepared in Step 1. Mechanically stir the MAO electrolyte at 50 rpm / min until the MAO process is complete. Maintain the electrolyte temperature at 20°C and MAO to obtain the inner layer.

[0079] Step 3, prepare anhydrous ethanol-KH550 aqueous solution, and perform interface transition treatment on the aluminum alloy micro-arc oxidation coating. Immerse the aluminum alloy micro-arc oxidation coating obtained in step 2 in anhydrous ethanol-KH550 solution for 30 minutes to form a transition layer. Then take out the workpiece and dry it in air or in an oven (60°C) for 45 minutes to ensure that the surface is completely dry. Further heat treatment (baking at 150°C for 60 minutes) is performed to enhance the interfacial bonding strength. The specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: 80% anhydrous ethanol, 18% pure water, and 2% KH550.

[0080] Step 4: Place the aluminum alloy obtained in step 3 into a drying oven and dry it at 60° C. for 45 min and then at 120° C. for 60 min.

[0081] Step 5, prepare an organic slurry containing nano silver copper alloy powder and FEVE fluorocarbon resin modified with rare earth lanthanum and holmium, and spray the organic slurry onto the surface of the aluminum alloy obtained in step 4 that has been subjected to micro-arc oxidation treatment to form an inner layer. The components and mass percentages of the modified organic slurry are: 7% nano silver copper alloy powder, 10% lanthanum nitrate, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the remainder are FEVE fluorocarbon resin and xylene, and the mass ratio of the FEVE fluorocarbon resin to xylene is 2:1. The spraying thickness is 50±5μm, the particle size of the nano silver copper alloy powder is 100-800 mesh, and the mass ratio of Ag to Cu is 1:4. The aluminum alloy coated with the organic modified coating is placed in a drying oven and dried at 30-40°C for 24 hours.

[0082] The prepared integrated coating has a uniform, dense and relatively smooth surface, completely covering the surface of the 5056 aluminum alloy.

[0083] Step 6, the aluminum alloy composite coating obtained in step 5 and the aluminum alloy substrate are subjected to electrochemical test, using a PARSTAT 4000A electrochemical workstation, with a platinum sheet as the auxiliary electrode, a saturated calomel electrode (SCE) as the reference electrode, and a three-electrode system. The corrosion performance of the 5056 aluminum alloy substrate and the aluminum alloy composite coating sample in natural seawater is studied by open circuit potential (OCP) measurement, potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) to evaluate the corrosion behavior of the sample in natural seawater. The 5056 aluminum alloy substrate and the aluminum alloy composite coating are subjected to OCP test for 1200s, and the scanning rate is 2mV·s -1 . The corrosion potential (E corr ) and the corrosion current density (i corr ) are calculated by Tafel extrapolation method. The sample is immersed in natural seawater solution for 20min to stabilize the open circuit potential. In the frequency range of 10mHz-100kHz, a sinusoidal alternating current perturbation with an amplitude of 10mV is applied to the 5056 aluminum alloy substrate, and a sinusoidal alternating current perturbation with an amplitude of 100mV is applied to the 5056 aluminum alloy composite coating.

[0084] From Figure 11 , Figure 12 , Figure 13 , it can be seen that the corrosion resistance of the magnesium alloy surface is greatly improved, the electrochemical corrosion potential moves greatly in the positive direction, and the self-corrosion current density is greatly reduced.

[0085] Step 7, the aluminum alloy composite coating obtained in step 5 and the aluminum alloy substrate are subjected to aspergillus flavus resistance test, and the 5056 aluminum alloy composite coating and the substrate are subjected to mildew resistance test according to GB / T1741-2020 "Paint film mildew resistance test method" 7.4.1 culture dish method. The test conditions are: time 14d, humidity 90%RH, temperature 28℃.

[0086] As Figure 14 shown, after the laboratory aspergillus flavus resistance test, the growth of mold on the surface of the coating is significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent mildew resistance performance.

[0087] Step 8, the aluminum alloy composite coating obtained in step 5 and the aluminum alloy substrate are subjected to diatom resistance test, taking new moon rhombus diatom as the research object, and the diatom resistance of the coating is studied. The specific test method is as follows: the diatom liquid is placed in a sterilized conical flask, sealed with an aerobic base film, and then placed in a light incubator for activation and expansion. The light intensity is set to 3000lux, the light and dark cycle is 12 / 12h, the temperature is 21±2℃, and the conical flask is shaken 1-3 times a day during the culture process. When the number of diatoms reaches 1×10 5When the diatom solution reached a concentration of 1000 diatoms / mL, the diatom solution was aliquoted, with 500 mL added to each conical flask. The aluminum alloy composite coating (20 mm x 30 mm x 5 mm) and the aluminum alloy substrate (20 mm x 30 mm x 5 mm) were then placed on the flask for antifouling performance testing. The incubation conditions were: light intensity of 3000 lux, a 12 / 12 h light / dark cycle, and a temperature of 21 ± 2°C. The conical flasks were shaken 1–3 times daily during the incubation period. The coatings were removed from the diatom solution at various time intervals and the surface was gently rinsed with PBS buffer. After diatom attachment, the number of attached diatoms was observed under a fluorescence microscope.

[0088] like Figure 15 As shown in the figure, after the anti-diatom experiment in the laboratory, the diatom attachment on the coating surface was significantly reduced compared with the surface of the 5056 aluminum alloy substrate, showing excellent anti-biofouling performance.

Claims

1. A micro-arc oxidation-rare earth modified FEVE composite coating on an aluminum alloy surface, characterized in that: The invention comprises an inner layer and an outer layer, wherein the inner layer is a corrosion-resistant ceramic layer containing niobium pentoxide, and the outer layer is a FEVE fluorocarbon resin organic layer modified with rare earth lanthanum or / and holmium containing silver-copper alloy powder.

2. The aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating according to claim 1, characterized in that: The thickness of the inner layer is 3-5 μm, and the thickness of the outer layer is 50±5 μm.

3. The aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating according to claim 1, characterized in that: The inner layer is prepared by a micro-arc oxidation process, and the outer layer is prepared by spraying.

4. The method for preparing the aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating according to claim 1, characterized in that: The steps include: Step 1: Clean and dry the aluminum alloy surface, and prepare a micro-arc oxidation electrolyte containing niobium pentoxide; Step 2: placing the cleaned aluminum alloy into the micro-arc oxidation electrolyte prepared in step 1, mechanically stirring the micro-arc oxidation electrolyte, and maintaining the electrolyte temperature at 15° C.-20° C. to perform micro-arc oxidation to obtain an inner layer; Step 3, preparing an anhydrous ethanol-KH550 aqueous solution to perform interface transition treatment on the aluminum alloy micro-arc oxidation coating: soaking the aluminum alloy micro-arc oxidation coating obtained in step 2 in an anhydrous ethanol-KH550 solution for 10-30 minutes, taking it out and drying it, and then heat treating it at 100-150° C. for 30-60 minutes to enhance the interface bonding strength of the coating surface; Step 4, drying the aluminum alloy obtained in step 3; Step 5: preparing an organic slurry containing nano silver-copper alloy powder and a FEVE fluorocarbon resin modified with rare earth lanthanum and / or holmium, spraying the organic slurry onto the surface of the aluminum alloy obtained in step 4 that has been subjected to micro-arc oxidation to form an inner layer, and drying the aluminum alloy coated with the organic modified coating; The micro-arc oxidation electrolyte includes: 9-11g / L sodium hexametaphosphate, 7-9g / L sodium silicate, 3-5g / L sodium hydroxide, and 5-7g / L niobium pentoxide; the organic slurry includes: by mass percentage, 5-7% nano silver copper alloy powder, 0-10% lanthanum nitrate, 0-10% holmium nitrate, 5-7% biuret, 11-13% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; the anhydrous ethanol-KH550 aqueous solution includes: by mass percentage, 75-85% anhydrous ethanol, 1-3% KH550, and the balance is water.

5. The preparation method according to claim 4, characterized in that The components and mass percentages of the organic slurry are: 6% nano silver-copper alloy powder, 10% lanthanum nitrate, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; or, 6% nano silver-copper alloy powder, 10% lanthanum nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; or, 6% nano silver-copper alloy powder, 10% holmium nitrate, 6% biuret, 12% anhydrous ethanol, and the balance is FEVE fluorocarbon resin and xylene; the mass ratio of the FEVE fluorocarbon resin to xylene is 2:

1.

6. The preparation method according to claim 4, characterized in that The micro-arc oxidation electrolyte includes: 10g / L sodium hexametaphosphate, 8g / L sodium silicate, 4g / L sodium hydroxide, and 6g / L niobium pentoxide.

7. The preparation method according to claim 4, characterized in that The specific components and mass percentages of the anhydrous ethanol-KH550 aqueous solution are: anhydrous ethanol 80%, pure water 18%, and KH550 2%.

8. The preparation method according to claim 4, characterized in that The particle size of the nano silver copper alloy powder is 100-800 mesh, and the mass ratio of Ag to Cu is 1:

4. The cleaning and drying of the aluminum alloy surface are performed by cleaning the aluminum alloy surface with deionized water and anhydrous ethanol, and drying it with a hair dryer; the step 4 is to place the aluminum alloy obtained in step 3 into a drying oven, and dry it at 60°C for 45 minutes and then at 120°C for 60 minutes; the drying of the aluminum alloy coated with the organic modified coating is to place the aluminum alloy coated with the organic modified coating into a drying oven, and dry it at 30-40°C for 24 hours; the aluminum alloy is 5056 aluminum alloy.

9. Use of the aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating according to claim 1 in anti-aflatoxin.

10. Use of the aluminum alloy surface micro-arc oxidation-rare earth modified FEVE composite coating according to claim 1 in anti-diatom treatment.

Images