Aluminum alloy surface super-hydrophobic nano coating and preparation method thereof

Abstract

The invention discloses a preparation method of an aluminum alloy surface super-hydrophobic nano coating, which is specifically implemented according to the following steps: step 1, after aluminum alloy is cleaned, acetone ultrasonic treatment is performed, anodic oxidation is performed in oxalic acid electrolyte, low temperature is maintained by using a cooling device, and an anodic oxidation aluminum alloy matrix is obtained after the process is finished; step 2, dissolving hexadecyl trimethyl ammonium bromide and triethanolamine with deionized water, adding sodium salicylate, heating and stirring until the solution is clear, then adding tetraethoxysilane and a curing agent, continuously stirring, and centrifugally drying to obtain dendritic nano SiO2; step 3, preparing dendritic nano SiO2 with a circular network structure; step 4, preparing an anodic aluminum oxide-based dendritic nano SiO2 composite coating; and step 5, depositing and curing the anodic aluminum oxide-based dendritic nano SiO2 composite coating by using dopamine. The invention also discloses a coating prepared by the method, and the anodic alumina-based dendritic nano SiO2 composite coating obtained by the method realizes double improvement of super-hydrophobicity and corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy surface protective coatings, and in particular relates to a method for preparing a super-phobic nano-coating on an aluminum alloy surface, and also relates to a coating prepared by the preparation method. Background Art

[0002] Aluminum alloys are widely used in many industrial fields due to their advantages such as light weight, high strength and good machinability. However, they are not suitable for corrosive media (especially Cl － ions) are susceptible to corrosion, including pitting and crevice corrosion. The naturally formed oxide film on the surface of aluminum alloys cannot provide effective corrosion protection. Anodizing is an effective surface treatment technology that uses aluminum and aluminum alloys as anodes. In a suitable electrolyte and under specific process conditions, an oxide film is formed on the surface through electrolysis. This changes the state and properties of the metal surface, thereby improving the corrosion resistance, wear resistance, high temperature resistance, and decorative properties of aluminum and aluminum alloys.

[0003] Hydrophobic materials are widely used in fields such as oil-gas separation, oil-water separation, seawater desalination, marine anti-corrosion and antifouling, antibacterial, drag reduction, anti-icing, and self-cleaning. They are typically prepared by combining surface micro- and nanostructure construction with low-surface-energy modification. Silicon dioxide (SiO2) can be considered an inorganic particle with a three-dimensional network structure. By grafting the abundant silanol groups on its surface, low-surface-energy materials can be introduced for microencapsulation and modification. Simultaneously, rigid particles are distributed on the coating surface to create the required roughness for a super-hydrophobic surface, thereby creating a super-hydrophobic material with exceptional wettability.

[0004] The Chinese patent "A Method for Anodic Oxidation of Aluminum Alloys with High Adhesion and Corrosion Resistance" (Application Number: CN201710838203.1, Authorization Number: CN109518252B) discloses a method for anodizing aluminum alloys to achieve high adhesion and corrosion resistance. The method involves degreasing, alkali washing, and pickling the aluminum alloy, then anodizing it with a mixed solution of sulfuric acid and aluminum sulfate. The resulting aluminum alloy anodized film exhibits high adhesion and corrosion resistance, but poor hydrophobicity. The Chinese patent "Anodizing Anticorrosion Treatment Method for Aluminum Alloys" (Application Number: CN201810312826.X, Authorization Number: CN108677234B) discloses a method for anodizing aluminum alloys to achieve corrosion resistance. By anodizing an aluminum substrate and then performing an anticorrosion treatment with a silane solution, a corrosion-resistant film is formed on the surface, significantly improving the corrosion resistance of the aluminum substrate. However, simply performing a silane treatment on the aluminum alloy after anodization results in poor corrosion resistance and hydrophobicity. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a super-phobic nano-coating on the surface of an aluminum alloy, which can enhance the corrosion resistance of the aluminum alloy surface while having hydrophobicity.

[0006] Another object of the present invention is to provide a coating prepared by a method for preparing a super-phobic nano-coating on an aluminum alloy surface.

[0007] The technical solution adopted by the present invention is a method for preparing a super-phobic nano-coating on an aluminum alloy surface, which is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treating it with acetone, anodizing it in an oxalic acid electrolyte, and maintaining the low temperature with a cooling device to obtain an anodized aluminum alloy substrate; Step 2: dissolving hexadecyltrimethylammonium bromide and triethanolamine in deionized water, adding sodium salicylate, heating and stirring until the solution is clear, then adding ethyl orthosilicate and a curing agent, continuing stirring, and centrifuging and drying to obtain dendritic nano-SiO2; Step 3, preparing dendritic nano-SiO2 with a circular network structure; Step 4, preparing an anodic aluminum oxide-based dendritic nano-SiO2 composite coating; Step 5: dopamine deposition and curing of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating.

[0008] The present invention is also characterized in that: Step 3 is specifically as follows: adding the dendritic nano-SiO2 to a cyclopentane solution of perfluoroalkyltriethoxysilane and stirring, drying to obtain modified dendritic nano-SiO2, and adding the modified dendritic nano-SiO2 to a tetrahydrofuran solution of polymethyl methacrylate to obtain dendritic nano-SiO2 with a circular network structure.

[0009] Step 4 is specifically as follows: dissolve tris(hydroxymethyl)aminomethane in deionized water, add the circular network structured dendritic nano-SiO2 prepared in step 3, ultrasonically disperse to obtain a nano-silica mixed solution, place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating.

[0010] Step 5 is specifically as follows: immersing the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in a tris(hydroxymethylaminomethane) solution, rapidly adding dopamine to the solution in the absence of light and continuously stirring, washing and drying the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and solidification.

[0011] In step 1, the electrolyte concentration of oxalic acid is 0.1mol / L-0.5mol / L, the cooling device temperature is set to -15℃--20℃, the constant current is 2A / dm², the current rise and fall rate is 0.06A / min-0.10A / min, the cathode is a platinum-coated steel mesh, and the distance between the anode and cathode is 6cm-10cm.

[0012] In step 2, hexadecyltrimethylammonium bromide is 0.5g-1.0g, triethanolamine is 1.0g-1.4g, sodium salicylate is 2.0g-3.0g, ethyl orthosilicate is 7.0g-9.0g, the curing agent is any one of KH550, KH560, KH570, and KH590, the addition amount is 1.5g-2.5g, deionized water is 40ml-50mL, and the stirring temperature is 60℃-80℃.

[0013] In step 3, the concentration of perfluoroalkyltriethoxysilane is 4 wt%-8 wt%, and the mass ratio of dendritic nano-SiO2 to polymethyl methacrylate added to the cyclopentane solution of perfluoroalkyltriethoxysilane is 6:1.

[0014] In step 4, the pH value of the tris(hydroxymethyl)aminomethane solution is 10, the amount of dendritic nano-SiO2 with a circular network structure is 2.0 g to 6.0 g, and ultrasonic dispersion is performed for 10 min to 15 min.

[0015] In step 5, the concentration of the tris(hydroxymethyl)aminomethane solution is 10 mmol / L, and the concentration of dopamine is 0.5 g-1.0 g.

[0016] Another technical solution adopted by the present invention is to prepare a coating using a method for preparing a super-phobic nano-coating on an aluminum alloy surface.

[0017] The beneficial effects of the present invention are: The preparation method of the super-hydrophobic nano-coating on the surface of an aluminum alloy of the present invention can obtain a composite coating that combines high-efficiency super-hydrophobicity and excellent corrosion resistance. By adjusting the anodizing parameters, an anodized aluminum alloy substrate with good performance is prepared on the aluminum alloy surface to enhance the corrosion resistance. After special modification, SiO2 is converted into dendritic nano-SiO2, which has a unique porous structure and can effectively improve the hydrophobicity of the coating. In addition, the dendritic nano-SiO2 is further modified to form a hydrophobic coating with a circular network structure. This structure can disperse the force of the impact to achieve better wear resistance. Finally, dopamine is spontaneously and uniformly deposited on the aluminum alloy surface to fix the dendritic nano-SiO2 on the aluminum alloy surface, which can effectively improve the bonding force of the coating. This novel composite coating not only provides super-hydrophobicity and corrosion resistance, but also has environmental advantages and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the microscopic morphology of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared by the present invention. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0020] The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: Prepare anodized aluminum alloy substrate After cleaning the aluminum alloy, ultrasonically treating with acetone, anodizing in an oxalic acid electrolyte, and maintaining the low temperature with a cooling device, the anodized aluminum alloy substrate is obtained. The electrolyte concentration of oxalic acid is 0.1mol / L-0.5mol / L, the cooling device temperature is set at -15℃--20℃, the constant current is 2A / dm² (0.32A), the current ramp rate is 0.06A / min-0.10A / min, the cathode is a platinum-coated steel mesh, and the distance between the anode and cathode is 6cm-10cm; Step 2: Preparation of dendritic nano-SiO2 Dissolve hexadecyltrimethylammonium bromide and triethanolamine in deionized water, add sodium salicylate, heat and stir until clear, then add ethyl orthosilicate and curing agent and continue stirring, centrifuge and dry to obtain dendritic nano-SiO2; Hexadecyltrimethylammonium bromide is 0.5g-1.0g, triethanolamine is 1.0g-1.4g, sodium salicylate is 2.0g-3.0g, ethyl orthosilicate is 7.0g-9.0g, the curing agent is any one of KH550, KH560, KH570, and KH590, the addition amount is 1.5g-2.5g, deionized water is 40ml-50mL, and the stirring temperature is 60℃-80℃; Step 3: Preparation of dendritic nano-SiO2 with circular network structure Adding dendritic nano-SiO2 to a cyclopentane solution of perfluoroalkyltriethoxysilane, stirring, and drying to obtain modified dendritic nano-SiO2, and adding the modified dendritic nano-SiO2 to a tetrahydrofuran solution of polymethyl methacrylate to obtain dendritic nano-SiO2 with a circular network structure; The concentration of perfluoroalkyltriethoxysilane is 4 wt%-8 wt%, and the mass ratio of dendritic nano-SiO2 to polymethyl methacrylate added to the cyclopentane solution of perfluoroalkyltriethoxysilane is 6:1; Step 4: Preparation of anodized aluminum-based dendritic nano-SiO2 composite coating Dissolve tris(hydroxymethyl)aminomethane in deionized water, add the circular network structure dendritic nano-SiO2 prepared in step 3, and disperse by ultrasonication to obtain a nano-silicon dioxide mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. The pH value of tris(hydroxymethyl)aminomethane solution is 10, the density of dendritic nano-SiO2 with circular network structure is 2.0g-6.0g, and ultrasonic dispersion is carried out for 10min-15min; Step 5, dopamine deposition and curing of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating; The anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 is immersed in a tris(hydroxymethylaminomethane) solution, dopamine is quickly added to the solution under light-free conditions and continuously stirred, and the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and solidification is washed and dried to obtain a superphobic nano-coating on the aluminum alloy surface; The concentration of the tris(hydroxymethyl)aminomethane solution is 10 mmol / L, and the concentration of dopamine is 0.5 g-1.0 g.

[0021] The present invention obtains a porous aluminum alloy matrix by anodizing the aluminum alloy surface. After special modification, SiO2 is converted into dendritic nano-SiO2, which has a unique porous structure and can effectively improve the hydrophobic ability of the coating. In addition, the dendritic nano-SiO2 is further modified to form a hydrophobic coating with a circular network structure. This structure can disperse the force of impact to achieve better wear resistance. Finally, with the help of dopamine, the dendritic nano-SiO2 is spontaneously and evenly deposited on the aluminum alloy surface, firmly adhering to the aluminum alloy surface, thereby effectively improving the bonding strength of the coating. Finally, an anodic aluminum-based dendritic nano-SiO2 composite coating is obtained, which achieves a dual improvement in super-hydrophobicity and anti-corrosion performance.

[0022] Example 1 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.1 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -20°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.06A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 6 cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 0.5 g of hexadecyltrimethylammonium bromide and 1.0 g of triethanolamine in 50 mL of deionized water, add 2.0 g of sodium salicylate, stir at 60°C until the solution is clear, then add 7.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 1.5 g of KH550 dropwise, stir for 2 h until the reaction is complete, and centrifuge to obtain dendritic nano-SiO2; Step 3: Add 3.0 g of dendritic nano-SiO2 to a 4 wt% perfluoroalkyltriethoxysilane cyclopentane solution, stir for 3 h, let stand for 30 min, and dry to obtain the modified dendritic nano-SiO2. Add the modified dendritic nano-SiO2 to a 0.5 g tetrahydrofuran solution of polymethyl methacrylate, and stir at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 2.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 10 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 0.5 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0023] Example 2 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.5 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -15°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.10A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 8cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 1.0 g of hexadecyltrimethylammonium bromide and 1.4 g of triethanolamine in 40 mL of deionized water, add 3.0 g of sodium salicylate, stir at 80°C until the solution is clear, then add 9.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 2.5 g of KH570 dropwise, stir for 2 h until the reaction is complete, and centrifuge to obtain dendritic nano-SiO2; Step 3: 12.0 g of dendritic nano-SiO2 was added to a cyclopentane solution of 8 wt% perfluoroalkyltriethoxysilane, stirred for 3 h, allowed to stand for 30 min, and dried to obtain the modified dendritic nano-SiO2. The modified dendritic nano-SiO2 was added to a tetrahydrofuran solution of 2.0 g polymethyl methacrylate, and stirred at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 6.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 15 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 1.0 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0024] Example 3 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.3 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -18°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.08A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 7cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 0.7 g of hexadecyltrimethylammonium bromide and 1.2 g of triethanolamine in 45 mL of deionized water, add 2.5 g of sodium salicylate, stir at 70 ° C until the solution is clear, then add 8.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 2.0 g of KH590 dropwise, and then stir for 2 h until the reaction is completed. Centrifuge and dry to obtain dendritic nano-SiO2; Step 3: Add 6.0 g of dendritic nano-SiO2 to a 6 wt% perfluoroalkyltriethoxysilane cyclopentane solution, stir for 3 h, let stand for 30 min, and dry to obtain the modified dendritic nano-SiO2. Add the modified dendritic nano-SiO2 to a 1.0 g tetrahydrofuran solution of polymethyl methacrylate, and stir at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 4.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 13 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 0.8 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0025] Example 4 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.2 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -18°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.06A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 8cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 0.9 g of hexadecyltrimethylammonium bromide and 1.3 g of triethanolamine in 40 mL of deionized water, add 2.0 g of sodium salicylate, and stir at 80°C until the solution is clear. Then, add 8.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 2.0 g of KH590 dropwise, and stir for 2 h until the reaction is complete. Centrifuge and dry to obtain dendritic nano-SiO2. Step 3: Add 6.0 g of dendritic nano-SiO2 to a cyclopentane solution of 8 wt% perfluoroalkyltriethoxysilane, stir for 3 h, let stand for 30 min, and dry to obtain the modified dendritic nano-SiO2. Add the modified dendritic nano-SiO2 to a tetrahydrofuran solution of 1.0 g polymethyl methacrylate, and stir at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 4.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 15 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 0.5 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0026] Example 5 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.4 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -17°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.09A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 9cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 0.7 g of hexadecyltrimethylammonium bromide and 1.4 g of triethanolamine in 45 mL of deionized water, add 2.5 g of sodium salicylate, stir at 65 ° C until the solution is clear, then add 8.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 2.5 g of KH590 dropwise, and then stir for 2 h until the reaction is completed. Centrifuge and dry to obtain dendritic nano-SiO2; Step 3: Add 6.0 g of dendritic nano-SiO2 to a 5 wt% perfluoroalkyltriethoxysilane cyclopentane solution, stir for 3 h, let stand for 30 min, and dry to obtain the modified dendritic nano-SiO2. Add the modified dendritic nano-SiO2 to a 1.0 g tetrahydrofuran solution of polymethyl methacrylate, and stir at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 5.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 13 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 0.8 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0027] Example 6 The method for preparing the super-phobic nano-coating on the surface of aluminum alloy of the present invention is specifically implemented according to the following steps: Step 1: After cleaning the aluminum alloy, ultrasonically treat it with acetone and perform anodization in a 0.3 mol / L oxalic acid electrolyte. A cooling device is used to maintain a low temperature of -18°C. Anodization is performed at a constant current of 2A / dm² (0.32A). The current is increased from 0A to 0.32A at a rate of 0.08A / min and maintained for 60 minutes. A platinum-coated steel mesh is used as the cathode. The distance between the anode and the cathode is 8cm. The reaction is completed to obtain an anodized aluminum alloy substrate. Step 2: Dissolve 0.9 g of hexadecyltrimethylammonium bromide and 1.3 g of triethanolamine in 50 mL of deionized water, add 2.0 g of sodium salicylate, stir at 80°C until the solution is clear, then add 8.0 g of ethyl orthosilicate dropwise, continue stirring for 2 h, add 2.0 g of KH570 dropwise, stir for 2 h until the reaction is complete, and centrifuge to obtain dendritic nano-SiO2; Step 3: Add 6.0 g of dendritic nano-SiO2 to a cyclopentane solution of 8 wt% perfluoroalkyltriethoxysilane, stir for 3 h, let stand for 30 min, and dry to obtain the modified dendritic nano-SiO2. Add the modified dendritic nano-SiO2 to a tetrahydrofuran solution of 1.0 g polymethyl methacrylate, and stir at 45° C. for 4 h to obtain a dendritic nano-SiO2 with a circular network structure. Step 4: Add tris(hydroxymethyl)aminomethane to 100 mL of deionized water and stir for 30 minutes until completely dissolved. Control the solution pH to 10, add 3.0 g of dendritic nano-SiO2 with a circular network structure, and ultrasonically disperse for 13 minutes to obtain a nano-silica mixed solution. Place the anodized aluminum alloy substrate in step 1 into the mixed solution, and stir at room temperature for 6 hours to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating. Step 5: Immerse the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 in 200 mL of 10 mmol / L tris(hydroxymethyl)aminomethane solution, quickly add 0.5 g of dopamine to the solution in the absence of light and stir continuously for 12 hours, wash and dry to obtain the anodic aluminum oxide-based dendritic nano-SiO2 composite coating after dopamine deposition and curing.

[0028] Table 1 is a comparison table of the hydrophobicity and corrosion resistance of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating in Example 4 and the anodic aluminum oxide-based dendritic nano-SiO2 composite coating in Comparative Examples 1-3. Comparative Example 1 is Example 4 with only the current rate modified to 0.20 A / min, Comparative Example 2 is Example 4 with the SiO2 unmodified, and Comparative Example 3 is Example 4 with the dendritic nano-SiO2 added in an amount of 10 g.

[0029] Table 1

[0030] As can be seen from Table 1, the coating in Example 4 has the best comprehensive performance. In the coating of Comparative Example 1, the current rise and fall rate during anodization is changed, resulting in the breakage of part of the oxide layer, which affects the anti-corrosion performance of the coating. In the coating of Comparative Example 2, SiO2 is not modified, resulting in a deterioration of its hydrophobicity, which in turn has a certain impact on the anti-corrosion performance. In Comparative Example 3, the amount of dendritic nano-SiO2 added is changed, and the dendritic nano-SiO2 particles are severely agglomerated, affecting its hydrophobicity and anti-corrosion performance. The anodized aluminum-based dendritic nano-SiO2 composite coating in Example 4 can enhance the anti-corrosion performance of the material after anodization. The unique center-radial pore structure of dendritic nano-silica can effectively improve the hydrophobic ability of the coating. Therefore, it has the best comprehensive performance and is better than all comparative examples.

[0031] Figure 1 This is a schematic diagram of the microscopic morphology of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared by the present invention. Figure 1 It can be seen that the dendritic nano-SiO2 particles are evenly attached to the surface of the anodized aluminum alloy substrate.

[0032] The present invention enhances corrosion resistance by anodizing the aluminum alloy surface. The specially modified SiO2 has a unique porous structure that can significantly enhance the hydrophobicity of the coating. In addition, the dendritic nano-SiO2 is further modified to construct a hydrophobic coating with a circular network structure, which can disperse the force of impact to achieve better wear resistance. Finally, dopamine is spontaneously and evenly deposited on the aluminum alloy surface to fix the dendritic nano-SiO2 to the aluminum alloy surface, which can effectively improve the bonding strength of the coating. This new composite coating not only provides super-hydrophobicity and corrosion resistance, but also has environmental advantages and broad application prospects.

Claims

1. A method for preparing a super-phobic nano-coating on an aluminum alloy surface, characterized in that: Please follow the steps below to implement: Step 1: After cleaning the aluminum alloy, ultrasonically treating it with acetone, anodizing it in an oxalic acid electrolyte, and maintaining the low temperature with a cooling device to obtain an anodized aluminum alloy substrate; Step 2: dissolving hexadecyltrimethylammonium bromide and triethanolamine in deionized water, adding sodium salicylate, heating and stirring until the solution is clear, then adding ethyl orthosilicate and a curing agent, continuing stirring, and centrifuging and drying to obtain dendritic nano-SiO2; Step 3, preparing dendritic nano-SiO2 with a circular network structure; Step 4, preparing an anodic aluminum oxide-based dendritic nano-SiO2 composite coating; Step 5: dopamine deposition and curing of the anodic aluminum oxide-based dendritic nano-SiO2 composite coating.

2. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein The step 3 is specifically as follows: adding the dendritic nano-SiO2 to a cyclopentane solution of perfluoroalkyltriethoxysilane and stirring, drying to obtain modified dendritic nano-SiO2, and adding the modified dendritic nano-SiO2 to a tetrahydrofuran solution of polymethyl methacrylate to obtain dendritic nano-SiO2 with a circular network structure.

3. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein The step 4 specifically comprises: dissolving tris(hydroxymethyl)aminomethane in deionized water, adding the circular network structured dendritic nano-SiO2 prepared in step 3, ultrasonically dispersing to obtain a nano-silica mixed solution, placing the anodized aluminum alloy substrate in step 1 into the mixed solution, and stirring at room temperature to obtain an anodized aluminum-based dendritic nano-SiO2 composite coating.

4. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein The step 5 specifically comprises: immersing the anodic aluminum oxide-based dendritic nano-SiO2 composite coating prepared in step 4 into a tris(hydroxymethylaminomethane) solution, rapidly adding dopamine to the solution under light-free conditions and continuously stirring, washing and drying the anodic aluminum oxide-based dendritic nano-SiO2 composite coating to obtain dopamine-deposited and solidified coating.

5. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein: In step 1, the electrolyte concentration of oxalic acid is 0.1 mol / L-0.5 mol / L, the cooling device temperature is set to -15°C--20°C, the constant current is 2 A / dm², the current rise and fall rate is 0.06 A / min-0.10 A / min, the cathode is a platinum-plated steel mesh, and the distance between the anode and the cathode is 6 cm-10 cm.

6. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein: In the step 2, the amount of cetyltrimethylammonium bromide is 0.5g-1.0g, the amount of triethanolamine is 1.0g-1.4g, the amount of sodium salicylate is 2.0g-3.0g, the amount of ethyl orthosilicate is 7.0g-9.0g, the curing agent is any one of KH550, KH560, KH570, and KH590, the amount added is 1.5g-2.5g, the amount of deionized water is 40ml-50mL, and the stirring temperature is 60°C-80°C.

7. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 2, wherein: In the step 3, the concentration of perfluoroalkyltriethoxysilane is 4 wt%-8 wt%, and the mass ratio of dendritic nano-SiO2 to polymethyl methacrylate added to the cyclopentane solution of perfluoroalkyltriethoxysilane is 6:

1.

8. The method for preparing the super-phobic nano-coating on the surface of aluminum alloy according to claim 3, wherein: In the step 4, the pH value of the tris(hydroxymethyl)aminomethane solution is 10, the amount of the dendritic nano-SiO2 with a circular network structure is 2.0 g to 6.0 g, and ultrasonic dispersion is performed for 10 min to 15 min.

9. The method for preparing a super-phobic nano-coating on an aluminum alloy surface according to claim 1, wherein: In the step 5, the concentration of the tris(hydroxymethyl)aminomethane solution is 10 mmol / L, and the concentration of dopamine is 0.5 g-1.0 g.

10. A coating prepared according to the method for preparing a super-phobic nano-coating on an aluminum alloy surface according to any one of claims 1 to 9.

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