Long-acting corrosion-resistant antifouling composite coating on surface of aluminum alloy and preparation method thereof

Abstract

The invention relates to an aluminum alloy surface long-acting corrosion-resistant antifouling composite coating and a preparation method thereof.The aluminum alloy surface long-acting corrosion-resistant antifouling composite coating comprises a porous ceramic film layer and a carbon nano tube / TiO2 compound modified epoxy coating, the carbon nano tube / TiO2 compound modified epoxy coating is arranged on the porous ceramic film layer, and the carbon nano tube / TiO2 compound modified epoxy coating is arranged on the porous ceramic film layer. The carbon nano tube / TiO2 compound modified epoxy coating is prepared from the following raw materials in parts by mass: 100 parts of epoxy resin, 2 to 25 parts of polyaniline coated carbon nano tube / TiO2 compound, 50 to 150 parts of dimethylformamide solvent, 50 to 100 parts of curing agent and 1 to 2 parts of flatting agent. According to the invention, a ceramic film layer and organic film layer composite protection technology is adopted, so that light metals such as aluminum alloy and the like can have relatively high strength and anti-corrosion and anti-fouling performance, and also have relatively high bonding strength and anti-aging performance.

Description

Technical Field

[0001] The present invention relates to the field of surface engineering, and specifically relates to a long-lasting corrosion-resistant and antifouling composite coating for aluminum alloy surfaces and a preparation method thereof. Background Technique

[0002] With the advancement of the marine power strategy and the rapid development of the marine economy, a large number of ships and equipment work in a harsh marine environment for a long time. At present, due to the demand for lightweight, a large amount of light metal materials such as aluminum alloy are used in marine equipment. If effective protection is not carried out, various types of corrosion such as chemical corrosion, electrochemical corrosion, and marine organism corrosion are likely to occur, greatly shortening the maintenance cycle and service life of equipment components, and causing huge losses to the use efficiency and economic benefits of the equipment. At present, coating organic antifouling and anticorrosion coatings can slow down corrosion and the problem of fouling corrosion caused by marine organism attachment, and are widely used in marine facilities and equipment such as ships. However, traditional anticorrosion coatings have a short corrosion-resistant life and require regular maintenance. Antifouling coatings also have problems such as toxicity, environmental pollution, and short life. In response to the anticorrosion and antifouling requirements of marine equipment, some domestic professional institutions have developed some environmentally friendly antifouling-corrosion-resistant organic coatings, generally using high-molecular compounds as the main film-forming substances, adding inorganic nano-fillers such as glass flakes, carbon nanotubes, and graphene to make the coatings have good corrosion resistance, and preventing microbial attachment by adding antifouling coatings such as cuprous oxide (Cu2O) and zinc oxide (ZnO). However, the Cu dissolved from the copper-containing antifouling agent will slowly penetrate into the coating interior. If it reaches the surface of the aluminum alloy substrate, it may accelerate corrosion. 2+ will slowly penetrate into the coating interior. If it reaches the surface of the aluminum alloy substrate, it may accelerate corrosion. Summary of the Invention

[0003] To solve the technical problems existing in the background technique, the present invention provides a long-lasting corrosion-resistant and antifouling composite coating for aluminum alloy surfaces and a preparation method thereof. On the surface of the aluminum alloy, a layer of Al2O3 ceramic film layer with a microporous structure is in-situ generated by micro-arc oxidation method, and then a layer of titanium oxide and modified carbon nanotube epoxy resin coating is coated on the surface of the ceramic film layer to prepare a ceramic / modified epoxy resin long-lasting corrosion-resistant and antifouling composite coating, solving the problems of single performance, poor bonding strength, and easy aging of traditional marine anticorrosion and antifouling epoxy coatings, and providing a new method for the long-lasting corrosion resistance and antifouling of marine equipment.

[0004] The technical solution of the present invention is as follows: The present invention relates to a long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy, which is characterized in that the long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy includes a porous ceramic film layer and a carbon nanotube / TiO2 composite modified epoxy coating. The carbon nanotube / TiO2 composite modified epoxy coating is disposed on the porous ceramic film layer. The carbon nanotube / TiO2 composite modified epoxy coating is prepared from the following raw materials in parts by mass: 100 parts of epoxy resin, 2 - 25 parts of polyaniline-coated carbon nanotube / TiO2 composite, 50 - 150 parts of dimethylformamide solvent, 50 - 100 parts of curing agent, and 1 - 2 parts of leveling agent.

[0005] Further, the carbon nanotube / TiO2 composite modified epoxy coating is prepared from the following raw materials in parts by mass: 100 parts of epoxy resin, 10 parts of polyaniline-coated carbon nanotube / TiO2 composite, 100 parts of dimethylformamide solvent, 100 parts of curing agent, and 1 part of leveling agent.

[0006] Further, the epoxy resin is E44, the curing agent is polyamide 650, and the leveling agent is BYK306.

[0007] Further, the porous ceramic film is an Al2O3 ceramic film layer with a porous structure.

[0008] A method for preparing the above-mentioned long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy is characterized in that the method includes the following steps:

[0009] 1) Preparation of the porous ceramic film layer on the surface of aluminum alloy:

[0010] After degreasing and defouling the surface of the aluminum alloy, immerse it in a micro-arc oxidation solution of a sodium hexametaphosphate system. Connect the positive electrode of the micro-arc oxidation power supply to the aluminum alloy and connect the negative electrode of the power supply. Control the current density at 1 - 10 A / dm 2 , the termination voltage is 500 - 600 V, the frequency is 100 - 1000 HZ, and the duty cycle is 30 - 60%. Perform micro-arc oxidation by this process to in-situ generate an Al2O3 ceramic film layer with a porous structure on the surface layer;

[0011] 2) Surface modification of carbon nanotubes:

[0012] Prepare a mixed solution of concentrated sulfuric acid and concentrated nitric acid. Place the carbon nanotubes in the mixed acid solution and treat them with ultrasonic oscillation for 0.5 - 1 h to fully disperse the carbon nanotubes. Then place them in a constant temperature water bath at 60 - 80 °C and stir for 0.5 - 1.5 h to allow the carbon nanotubes to fully react with the mixed acid solution; then wash the filtered carbon nanotubes 3 - 5 times with deionized water, and then dry the washed carbon nanotubes at 60 - 80 °C to obtain acidified carbon nanotubes;

[0013] 3) Surface modification of nano-TiO2:

[0014] Prepare an ethanol solution, then add a silane coupling agent, and after ultrasonic oscillation for 0.5 - 1.5 h, obtain Solution A; then, disperse nano-TiO₂ in a xylene solution, and after ultrasonic oscillation for 0.5 - 1.5 h, obtain Solution B; then add Solution B to Solution A, and react fully with the silane coupling agent at a constant temperature of 50 - 70 °C for 0.5 - 1.5 h, filter the nano-TiO₂, wash it with alcohol, and dry it in a constant-temperature oven at 50 - 70 °C for 6 - 10 h;

[0015] 4) Preparation of carbon nanotube / nano-TiO₂ composite:

[0016] Prepare an ethanol aqueous solution, mix carbon nanotubes and TiO₂ powder in a certain proportion in the ethanol solution, stir at room temperature for 2 - 6 h, and utilize the carboxyl and other oxygen-containing functional groups on the surface of acidified carbon nanotubes and the abundant hydroxyl groups and nano-effects on the surface of nano-TiO₂ to achieve the composite of carbon nanotubes and TiO₂ through electrostatic adsorption and intermolecular hydrogen bonding in the aqueous dispersion system. After the reaction, obtain the carbon nanotube / TiO₂ composite through vacuum filtration, wash it 3 - 5 times with deionized water, and dry it in an oven at 50 - 80 °C for 4 - 8 h to obtain the carbon nanotube / TiO₂ composite;

[0017] 5) Polyaniline-coated carbon nanotube / TiO₂ composite:

[0018] Add the carbon nanotube / TiO₂ composite to hydrochloric acid and aniline with a concentration of 0.5 mol / L, carry out mechanical stirring reaction for 0.5 - 1.5 h to form a uniform suspension; then, add an ammonium persulfate solution, and carry out oxidation polymerization reaction for 4 - 8 h under ice bath. Wash the precipitate 3 times with deionized water and dry it at 60 - 80 °C to obtain the polyaniline-coated carbon nanotube / TiO₂ composite;

[0019] 6) Preparation of carbon nanotube / TiO₂ composite-modified epoxy coating:

[0020] Add the polyaniline-coated carbon nanotube / TiO₂ composite obtained in step 5) to a dimethylformamide solvent, ultrasonically oscillate for 1 h, and then add epoxy resin E44, and mechanically stir for 0.5 - 1 h to obtain the carbon nanotube / TiO₂ composite-modified epoxy coating;

[0021] 7) Preparation of carbon nanotube / TiO₂ composite-modified epoxy coating:

[0022] In the carbon nanotube / TiO2 composite modified epoxy material prepared in step 6), add polyamide 650 curing agent and BYK306 leveling agent, mechanically stir for 0.5 - 1 h, and after mixing evenly, coat it onto the porous ceramic film layer on the aluminum alloy surface prepared in step 1) by brushing or spraying method. Then dry it at room temperature for 12 - 24 h, and then continue to cure it at 70 - 80 °C in a vacuum oven for 6 - 8 h to obtain a carbon nanotube / TiO2 composite modified epoxy coating.

[0023] Further, in step 1), the formula of the sodium hexametaphosphate system micro-arc oxidation solution is: (NaPO3)6 20 g / L, NaOH 1 g / L, Na2WO4 5 g / L.

[0024] Further, in step 2), the ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, the concentration of concentrated sulfuric acid is 95% - 98%, the concentration of concentrated nitric acid is 65% - 68%, the outer diameter of the carbon nanotubes is 20 - 30 nm, the inner diameter is 5 - 10 nm, and the length is 10 - 20 μm.

[0025] Further, in step 3), the average particle size of the nano-TiO2 is 10 - 50 nm, and in step 4), the mass ratio of carbon nanotubes to TiO2 powder is 1:4 - 10.

[0026] Further, in steps 3) and 4), the volume ratio of ethanol to deionized water in the ethanol aqueous solution is 4:1, that is, V(C2H5OH):V(H2O) = 4:1, the ethanol is of analytical purity with a concentration of 95%, and the resistivity of deionized water is ≥15 MΩ·m.

[0027] Further, in steps 6) and 7), the mechanical stirring speed is 200 r / min.

[0028] A long-term corrosion-resistant and anti-fouling composite coating for aluminum alloy surface and its preparation method provided by the present invention first in-situ generates a layer of Al2O3 ceramic film layer with a microporous structure on the aluminum alloy surface by micro-arc oxidation method. On the other hand, modified carbon nanotubes and nano-TiO2 are obtained through surface modification, then nano-titanium oxide is grafted onto the surface of the carbon nanotubes to obtain a carbon nanotube / TiO2 composite, and then polyaniline is used to coat the carbon nanotube / TiO2 composite. Finally, the coated carbon nanotube / TiO2 composite is added as a reinforcing phase into the resin matrix to make a modified epoxy resin coating. Finally, the prepared modified epoxy resin coating is coated or sprayed on the surface of the Al2O3 ceramic film layer with a microporous structure to realize the preparation of a long-term corrosion-resistant and anti-fouling composite coating on the aluminum alloy surface. Therefore, the present invention has the following advantages:

[0029] 1) The present invention adopts the composite protection technology of ceramic film layer and organic film layer, which can endow light metals such as aluminum alloy with high strength, anti-corrosion and anti-fouling properties, and at the same time has high bonding strength and anti-aging performance.

[0030] 2) The present invention prepares a composite of nano-TiO2 and carbon nanotubes and adds it to epoxy resin, which can uniformly disperse nano-TiO2 and carbon nanotubes in the epoxy resin matrix, solving the problem that nano-TiO2 is extremely easy to agglomerate in the resin matrix.

[0031] 3) The present invention adopts a method combining in-situ generated Al2O3 ceramic film layer with porous structure on the surface and organic film layer. The epoxy resin penetrates into the micropores of the ceramic film layer, realizing the interlocking phenomenon of the ceramic film layer and the epoxy resin film layer in the physical structure, which can greatly improve the bonding strength of the epoxy resin coating.

[0032] 4) The present invention coats a modified epoxy resin coating on the surface of the ceramic film layer to realize the function of the organic film layer to seal the micropores of the ceramic film layer, preventing corrosive media from entering the micropores of the ceramic film layer and causing corrosion.

[0033] 5) The present invention adds TiO2 to the epoxy resin, which not only endows the coating with bactericidal and anti-fouling properties, but also can utilize the strong absorption ability of TiO2 to ultraviolet rays to well shield ultraviolet rays and slow down the aging of the epoxy coating.

[0034] 6) The present invention uses the conductive polymer polyaniline to coat nano-TiO2. Polyaniline not only improves the photoelectric conversion efficiency of TiO2 as a sensitizer, but also has excellent corrosion resistance, making the coating have good comprehensive anti-corrosion and anti-fouling properties. Brief Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the long-term corrosion-resistant and anti-fouling composite coating of the present invention;

[0036] Figure 2 It is a schematic structural diagram of the carbon nanotube / TiO2 composite of the present invention.

[0037] The reference numerals are as follows:

[0038] 1. Carbon nanotube / TiO2 composite modified epoxy coating; 2. Porous ceramic film layer; 3. Aluminum alloy matrix; 4. Nano-TiO2; 5. Carbon nanotube. Detailed Embodiments

[0039] The following further describes the present invention in detail with reference to the drawings and specific embodiments:

[0040] See Figure 1The long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy of the present invention comprises a porous ceramic film layer 2 and a carbon nanotube / TiO2 composite modified epoxy coating 1, wherein the carbon nanotube / TiO2 composite modified epoxy coating 2 is arranged on the porous ceramic film layer 2, and the porous ceramic film layer 2 is arranged on the surface of the aluminum alloy substrate 3, wherein the carbon nanotube / TiO2 composite modified epoxy coating 1 comprises the following raw materials by mass: 100 parts of epoxy resin, 2 to 25 parts of polyaniline-coated carbon nanotube / TiO2 composite, 50 to 150 parts of dimethylformamide solvent, 50 to 100 parts of curing agent, and 1 to 2 parts of leveling agent. In a specific embodiment of the present invention, the carbon nanotube / TiO2 composite modified epoxy coating comprises the following raw materials by mass: 100 parts of epoxy resin, 10 parts of polyaniline-coated carbon nanotube / TiO2 composite, 100 parts of dimethylformamide solvent, 100 parts of curing agent, and 1 part of leveling agent. The epoxy resin is E44, the curing agent is polyamide 650, and the leveling agent is BYK 306. The porous ceramic membrane is an Al2O3 ceramic membrane layer with a porous structure.

[0041] The thickness of the porous ceramic film layer 2 micro-arc oxidation film layer is 30-50 μm, and the thickness of the carbon nanotube / TiO2 composite modified epoxy coating layer 1 is 100-500 μm. In a specific embodiment of the present invention, the thickness of the porous ceramic film layer 2 micro-arc oxidation film layer is 30 μm, and the thickness of the carbon nanotube / TiO2 composite modified epoxy coating layer 1 is 150 μm.

[0042] The present invention is to prepare a ceramic film layer with a microporous structure on the surface of an aluminum alloy, then add a polyaniline-coated carbon nanotube and titanium dioxide (TiO2) composite to an epoxy resin coating, utilize the photocatalytic semiconductor antibacterial and antifouling properties of TiO2 and the corrosion resistance of polyaniline and carbon nanotubes to make the modified epoxy coating have both anticorrosion and antifouling properties, and then apply or spray the carbon nanotube / TiO2 composite modified epoxy resin coating on the surface of the Al2O3 ceramic film layer with a microporous structure, so as to achieve the preparation of a long-term corrosion-resistant and antifouling composite coating with high bonding strength on the surface of the aluminum alloy. The steps of the specific embodiment are as follows:

[0043] 1) Preparation of porous ceramic film layer on aluminum alloy surface.

[0044] After degreasing and cleaning the aluminum alloy surface, immerse it in a sodium hexametaphosphate system micro-arc oxidation solution with a formula of (NaPO3) 620g / L, NaoH 1g / L, and Na2WO45g / L. Connect the aluminum alloy to the positive electrode of the micro-arc oxidation power supply and connect the cathode of the power supply. Use the cross-current method to control the current density to 5A / dm 2 The micro-arc oxidation process is carried out with a termination voltage of 550V, a frequency of 500HZ, and a duty cycle of 50%, and an Al2O3 ceramic film layer with a porous structure on the surface is generated in situ.

[0045] 2) Surface modification of carbon nanotubes.

[0046] Prepare a mixed solution of concentrated sulfuric acid and concentrated nitric acid. The concentration of concentrated sulfuric acid is 95% - 98%, the concentration of concentrated nitric acid is 65% - 68%, and the ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1. Place 5 g of carbon nanotubes with an outer diameter of (20 - 30) nm, an inner diameter of (5 - 10) nm, and a length of (10 - 20) μm into the mixed acid solution, and treat it with ultrasonic oscillation for 0.5 h to fully disperse the carbon nanotubes. Then place it in a constant temperature water bath at 80 °C and stir for 0.5 h to allow the carbon nanotubes to react fully with the mixed acid solution. Then wash the filtered carbon nanotubes with deionized water 3 times, and then dry the washed carbon nanotubes at 80 °C to obtain acidified carbon nanotubes.

[0047] 3) Surface modification of nano-TiO₂.

[0048] Prepare an ethanol solution with a volume ratio of ethanol to deionized water of 4:1 (V(C₂H₅OH):V(H₂O) = 4:1). The ethanol is of analytical purity with a concentration of 95%, and the resistivity of deionized water is ≥15 MΩ·m. Then add the silane coupling agent KH540 and ultrasonically oscillate for 0.5 h to obtain solution A. Disperse 25 g of nano-TiO₂ with an average particle size of 10 nm in xylene solution and ultrasonically oscillate for 1 h to obtain solution B. Add solution B to solution A and react fully with the silane coupling agent at a constant temperature of 60 °C for 1 h. Then filter the nano-TiO₂, wash it with alcohol, and dry it in a constant temperature oven at 60 °C for 8 h.

[0049] 4) As Figure 2 shown, preparation of the nano-TiO₂ 4 and carbon nanotube 5 composite.

[0050] Prepare an ethanol aqueous solution with a volume ratio of ethanol to deionized water of 4:1 (V(C₂H₅OH):V(H₂O) = 4:1). The ethanol is of analytical purity with a concentration of 95%, and the resistivity of deionized water is ≥15 MΩ·m. Mix the carbon nanotubes 5 and TiO₂ powder in a ratio of 1:5 in the ethanol solution and stir at room temperature for 4 h. Utilize the carboxyl and other oxygen-containing functional groups on the surface of the acidified carbon nanotubes and the abundant hydroxyl groups and nano-effects on the surface of nano-TiO₂ to achieve the composite of carbon nanotubes and TiO₂ through electrostatic adsorption and intermolecular hydrogen bonding in the aqueous dispersion system. After the reaction, obtain the carbon nanotube / TiO₂ composite through vacuum filtration, wash it with deionized water 3 times, and dry it in an 80 °C oven for 6 h to obtain the carbon nanotube / TiO₂ composite.

[0051] 5) Polyaniline-coated carbon nanotube / TiO₂ composite.

[0052] The carbon nanotube / TiO2 composite was added to hydrochloric acid and aniline with a concentration of 0.5 mol / L, and mechanically stirred for 1 h to form a uniform suspension. Then, ammonium persulfate solution was added, and oxidative polymerization reaction was carried out for 6 h under an ice bath. The precipitate was washed 3 times with deionized water and dried at 80 °C to obtain the carbon nanotube / TiO2 composite coated with polyaniline.

[0053] 6) Preparation of carbon nanotube / TiO2 composite modified epoxy coating.

[0054] 10 parts of the carbon nanotube / TiO2 composite coated with polyaniline obtained in step 5) was added to N,N-dimethylformamide solvent (100 parts), and ultrasonically oscillated for 1 h. Then, 100 parts of epoxy resin E44 was added, and mechanically stirred at 200 r / min for 1 h to obtain the carbon nanotube / TiO2 composite modified epoxy coating.

[0055] 7) Preparation of carbon nanotube / TiO2 composite modified epoxy coating.

[0056] 100 parts of the carbon nanotube / TiO2 composite modified epoxy material prepared in step 6) was added with polyamide 650 curing agent (100 parts) and leveling agent (1 part), and mechanically stirred at 200 r / min for 1 h. After mixing evenly, it was coated onto the porous ceramic film layer on the aluminum alloy surface prepared in step 1 by brushing method, then dried at room temperature for 12 h, and then cured at 80 °C in a vacuum oven for 8 h to obtain the carbon nanotube / TiO2 composite modified epoxy coating.

[0057] The above is only the specific implementation manner disclosed by the present invention, but the protection scope disclosed by the present invention is not limited thereto. The protection scope disclosed by the present invention shall be subject to the protection scope of the claims.

[0058] The technical content not specifically described in the content of the present invention and the above embodiments is the same as the prior art.

[0059] The present invention is not limited to the above embodiments, and all the contents described in the present invention can be implemented and have the said good effects.

Claims

1. A long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy, characterized in that: The long-lasting corrosion-resistant and anti-fouling composite coating on the surface of the aluminum alloy comprises a porous ceramic film layer and a carbon nanotube / TiO2 composite modified epoxy coating. The carbon nanotube / TiO2 composite modified epoxy coating is arranged on the porous ceramic film layer. The carbon nanotube / TiO2 composite modified epoxy coating comprises the following raw materials in parts by mass: 100 parts of epoxy resin, 2 to 25 parts of polyaniline-coated carbon nanotube / TiO2 composite, 50 to 150 parts of dimethylformamide solvent, 50 to 100 parts of curing agent, and 1 to 2 parts of leveling agent.

2. The long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy according to claim 1, characterized in that: The carbon nanotube / TiO2 composite modified epoxy coating comprises the following raw materials by mass: 100 parts of epoxy resin, 10 parts of polyaniline coated carbon nanotube / TiO2 composite, 100 parts of dimethylformamide solvent, 100 parts of curing agent and 1 part of leveling agent.

3. The long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy according to claim 1 or 2, characterized in that: The epoxy resin is E44, the curing agent is polyamide 650, and the leveling agent is BYK306.

4. The long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy according to claim 3 is characterized by: The porous ceramic membrane is an Al2O3 ceramic membrane layer with a porous structure.

5. A method for preparing the long-lasting corrosion-resistant and antifouling composite coating on the surface of aluminum alloy according to claim 1, characterized in that: The method comprises the following steps: 1) Preparation of porous ceramic film on aluminum alloy surface: After the aluminum alloy surface is degreased and cleaned, it is immersed in a sodium hexametaphosphate system micro-arc oxidation solution. The aluminum alloy is connected to the positive electrode of the micro-arc oxidation power supply and the cathode of the power supply. The cross-current method is used to control the current density to 1-10A / dm 2 , the termination voltage is 500-600V, the frequency is 100-1000HZ, and the duty cycle is 30-60% to perform micro-arc oxidation, and an Al2O3 ceramic film layer with a porous structure on the surface is generated in situ; 2) Surface modification of carbon nanotubes: Prepare a mixed solution of concentrated sulfuric acid and concentrated nitric acid, place the carbon nanotubes in the mixed acid solution, treat with ultrasonic oscillation for 0.5 to 1 hour to fully disperse the carbon nanotubes, and then place in a 60 to 80° C. constant temperature water bath and stir for 0.5 to 1.5 hours to fully react the carbon nanotubes with the mixed acid solution; then wash the filtered carbon nanotubes with deionized water for 3 to 5 times, and then dry the washed carbon nanotubes at 60 to 80° C. to obtain acidified carbon nanotubes; 3) Surface modification of nano-TiO2: Prepare an ethanol solution, then add a silane coupling agent, and ultrasonically vibrate for 0.5 to 1.5 hours to obtain a solution A; then, disperse nano-TiO2 in a xylene solution, and ultrasonically vibrate for 0.5 to 1.5 hours to obtain a solution B; then add the solution B to the solution A, and fully react with the silane coupling agent at a constant temperature of 50 to 70°C for 0.5 to 1.5 hours, filter the nano-TiO2, wash with alcohol, and dry in a constant temperature oven at 50 to 70°C for 6 to 10 hours; 4) Preparation of nano-TiO2 and carbon nanotube composites: An ethanol aqueous solution is prepared, carbon nanotubes and TiO2 powder are mixed in a certain proportion in the ethanol solution, stirred at room temperature for 2 to 6 hours, and the carbon nanotubes and TiO2 are compounded in a water dispersion system by electrostatic adsorption and intermolecular hydrogen bonds using oxygen-containing functional groups such as carboxyl groups on the surface of the acidified carbon nanotubes and abundant hydroxyl groups and nano-effects on the surface of nano-TiO2. After the reaction is completed, a carbon nanotube / TiO2 composite is obtained by vacuum filtration, washed with deionized water for 3 to 5 times, and dried in an oven at 50 to 80° C. for 4 to 8 hours to obtain a carbon nanotube / TiO2 composite; 5) Polyaniline coated carbon nanotube / TiO2 composite: The carbon nanotube / TiO2 complex was added to 0.5 mol / L hydrochloric acid and aniline, and mechanically stirred for 0.5 to 1.5 hours to form a uniform suspension; then, an ammonium persulfate solution was added and oxidative polymerization was carried out in an ice bath for 4 to 8 hours. The precipitate was washed with deionized water for 3 times and dried at 60 to 80°C to obtain a polyaniline-coated carbon nanotube / TiO2 complex; 6) Preparation of carbon nanotube / TiO2 composite modified epoxy coating: The carbon nanotube / TiO2 composite coated with polyaniline obtained in step 5) is added to a dimethylformamide solvent and ultrasonically vibrated for 1 hour, and then epoxy resin E44 is added and mechanically stirred for 0.5 to 1 hour to obtain a carbon nanotube / TiO2 composite modified epoxy coating; 7) Preparation of carbon nanotube / TiO2 composite modified epoxy coating: Add polyamide 650 curing agent and BYK306 leveling agent to the carbon nanotube / TiO2 composite modified epoxy material prepared in step 6), stir mechanically for 0.5-1h, mix evenly, and then apply it to the porous ceramic film layer on the surface of the aluminum alloy prepared in step 1) by brushing or spraying, then dry at room temperature for 12-24h, and then continue to cure in a vacuum oven at 70-80°C for 6-8h to obtain a carbon nanotube / TiO2 composite modified epoxy coating.

6. The method for preparing a long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy according to claim 5, characterized in that: In the step 1), the formula of the sodium hexametaphosphate system micro-arc oxidation solution is: (NaPO3) 620g / L, NaoH 1g / L, Na2WO45g / L.

7. The method for preparing a long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy according to claim 6, characterized in that: In the step 2), the ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, the concentration of concentrated sulfuric acid is 95% to 98%, the concentration of concentrated nitric acid is 65% to 68%, the outer diameter of the carbon nanotubes is 20 to 30 nm, the inner diameter is 5 to 10 nm, and the length is 10 to 20 μm.

8. The method for preparing a long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy according to claim 7, characterized in that: In the step 3), the average particle size of nano-TiO2 is 10-50 nm, and in the step 4), the mass ratio of carbon nanotubes to TiO2 powder is 1:4-10.

9. The method for preparing a long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy according to claim 8, characterized in that: In step 3) and step 4), the volume ratio of ethanol to deionized water in the ethanol aqueous solution is 4:1, that is, V(C2H5OH):V(H2O)=4:1, the ethanol is analytically pure at a concentration of 95%, and the resistivity of the deionized water is ≥15MΩ·m.

10. The method for preparing a long-lasting corrosion-resistant and antifouling composite coating on the surface of an aluminum alloy according to claim 9, characterized in that: In step 6) and step 7), the mechanical stirring speed is 200 r / min.

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