Method for preparing super-hydrophobic coating on surface of aluminum alloy

Abstract

The invention relates to the technical field of aluminum alloy hydrophobic coating preparation, and particularly discloses a method for preparing an aluminum alloy surface super-hydrophobic coating, and the method comprises the following steps: pretreatment: placing an aluminum alloy sample in a plasma reaction chamber for treatment by using a radio frequency plasma generator; performing micro-arc oxidation, namely performing micro-arc oxidation on the pretreated aluminum alloy sample by adopting a direct-current pulse power supply by taking sodium silicate (Na2S O3) as a basic electrolyte; and stearic acid modification: soaking the aluminum alloy sample subjected to micro-arc oxidation in a stearic acid solution, stirring at a constant temperature, taking out, cleaning, and drying to obtain the aluminum alloy sample surface super-hydrophobic coating. According to the method, the aluminum alloy sample subjected to micro-arc oxidation is subjected to stearic acid modification, the surface energy of the surface of the aluminum alloy sample is greatly reduced, the hydrophobic performance of the aluminum alloy is improved, meanwhile, the bonding strength of micro-arc oxidation and stearic acid is enhanced through pretreatment, and the hydrophobic performance and durability of the hydrophobic coating are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing aluminum alloy hydrophobic coatings, and in particular to a method for preparing a super hydrophobic coating on the surface of an aluminum alloy. Background Art

[0002] Aluminum and its alloys are widely used in many fields such as automotive industry, aerospace, medical equipment, military defense, and 3C products due to their low density, high specific strength, and easy processing and forming. However, aluminum alloys have poor corrosion resistance due to their poor surface hydrophobicity, which greatly limits the scope of application and service life of aluminum alloy materials.

[0003] Micro-arc oxidation (MAO), also known as plasma electrolytic oxidation (PEO), is a new surface treatment technology developed on the basis of anodizing technology. The principle of micro-arc oxidation is to use the high temperature and high pressure generated by micro-arc discharge to cause rapid melting and cooling of the metal surfaces such as aluminum and magnesium, and to adsorb the ionic components in the electrolyte to grow a layer of high-quality corrosion-resistant and wear-resistant ceramic coating in situ on the surface. Compared with other surface treatment methods, micro-arc oxidation has the advantages of simple operation, controllable coating, and low environmental pollution. It is expected to become a new method to solve the corrosion problem of aluminum alloys. However, discharge holes and cracks will inevitably be generated during the preparation of PEO coatings, which provides opportunities for corrosive ions to enter the corrosion surface of the coating, greatly reducing the corrosion resistance of the coating in application.

[0004] There are generally two solutions to this problem in the prior art: one is to improve the hydrophobicity of the PEO coating by adding fluoride to the electrolyte to introduce fluorine into the PEO coating (such as CN106835234A), but the addition of fluoride to the electrolyte will increase the cost of the electrolyte and make the composition of the electrolyte more complicated, requiring more precise control of process parameters to produce better hydrophobicity; the other is to add stearic acid to the electrolyte to react with the surface of the PEO coating to reduce the surface energy (such as CN118835243A), but the addition of stearic acid as an organic component will affect the stability of the electrolyte, and it is easy to decompose or deteriorate during the micro-arc oxidation process, thereby affecting the quality and performance consistency of the coating, and the chemical bonding between stearic acid and the coating is not strong enough, and the service life is low.

[0005] Therefore, it is necessary to design a method for preparing an aluminum alloy hydrophobic coating to solve the problems of low service life, high cost and complex preparation of the aluminum alloy hydrophobic coating prepared in the prior art. Summary of the invention

[0006] In view of this, the present invention proposes a method for preparing an aluminum alloy hydrophobic coating, aiming to solve the problems of low service life, high cost and complex preparation of the aluminum alloy hydrophobic coating prepared in the prior art.

[0007] The present invention provides a method for preparing an aluminum alloy hydrophobic coating, comprising:

[0008] Pretreatment: Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber and perform plasma treatment for 5-10 minutes;

[0009] Micro-arc oxidation: The pretreated aluminum alloy is used as the anode and fixed on the fixture of the micro-arc oxidation equipment. The stainless steel plate is used as the cathode and placed in the electrolytic cell filled with electrolyte. After adjusting the micro-arc oxidation process parameters, micro-arc oxidation begins.

[0010] Stearic acid modification: After the micro-arc oxidation is completed, the aluminum alloy sample after micro-arc oxidation is immersed in a stearic acid solution and stirred at a constant temperature of 60-80°C for 2-3 hours. The sample is then taken out, cleaned with ethanol and dried. After drying, a super-hydrophobic coating is obtained on the surface of the aluminum alloy.

[0011] Furthermore, in the plasma treatment, argon gas is used as the working gas, the gas flow rate is controlled at 20-30 mL / min, the pressure in the chamber is maintained at 30-50 Pa; and the RF power is set to 100-150W.

[0012] Furthermore, the electrolyte components in the micro-arc oxidation include: 100 parts of water, 10-15 parts of sodium silicate and 2-3 parts of sodium phosphate.

[0013] Furthermore, the preparation method of the electrolyte is: dissolving 10-15 parts of sodium silicate into 100 parts of water, adding potassium hydroxide (KOH) to adjust the pH value to 11-13, and adding 2-3 parts of sodium phosphate and stirring evenly to obtain the electrolyte.

[0014] Furthermore, the micro-arc oxidation process parameters are: voltage of 350-400V, pulse frequency of 500-800Hz, duty cycle of 20%-30% and processing time of 10-15 minutes.

[0015] Furthermore, the stearic acid solution comprises: 100 parts of ethanol, 5-10 parts of stearic acid and 0.1-0.2 parts of a catalyst.

[0016] Furthermore, the catalyst is one of dibutyltin dilaurate, tetraisopropyl titanate and tetrabutyl zirconate.

[0017] Furthermore, the drying temperature in the stearic acid modification is 80-100° C., and the drying time is 1-2 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: by first micro-arc oxidation of the aluminum alloy and then stearic acid modification of the aluminum alloy after micro-arc oxidation, it is no longer necessary to add a stearic acid solution to the electrolyte, thereby ensuring the consistency of the coating and improving the hydrophobicity of the coating; at the same time, by plasma treatment of the aluminum alloy, active sites are formed on the surface of the aluminum alloy, so that the stearic acid molecules and the micro-arc oxidation coating form a stronger chemical bond, thereby improving the bonding force between the stearic acid and the coating, so that the stearic acid can be more firmly attached to the surface of the coating, reducing the shedding of stearic acid during use, and improving the hydrophobicity and durability of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0020] Figure 1 A flow chart of a method for preparing a super-hydrophobic coating on an aluminum alloy surface provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] Micro-arc oxidation (MAO), also known as plasma electrolytic oxidation (PEO), is a new surface treatment technology developed on the basis of anodizing technology. The principle of micro-arc oxidation is to use the high temperature and high pressure generated by micro-arc discharge to cause rapid melting and cooling of the metal surfaces such as aluminum and magnesium, and to adsorb the ionic components in the electrolyte to grow a layer of high-quality corrosion-resistant and wear-resistant ceramic coating in situ on the surface. Compared with other surface treatment methods, micro-arc oxidation has the advantages of simple operation, controllable coating, and low environmental pollution. It is expected to become a new method to solve the corrosion problem of aluminum alloys. However, discharge holes and cracks will inevitably be generated during the preparation of PEO coatings, which provides opportunities for corrosive ions to enter the corrosion surface of the coating, greatly reducing the corrosion resistance of the coating in application.

[0023] There are generally two solutions to this in the prior art: one is to improve the hydrophobicity of PEO coating by introducing fluorine element into PEO coating by adding fluoride in electrolyte (such as CN106835234A), but the composition of electrolyte becomes more complicated while fluoride is added to electrolyte to increase the cost of electrolyte, and it is necessary to more accurately control process parameters to produce better hydrophobicity; the second is to reduce surface energy (such as CN118835243A) by adding stearic acid and PEO coating surface reaction in electrolyte, but the addition of organic component stearic acid can affect the stability of electrolyte, and decomposition or deterioration is easy to occur during micro-arc oxidation, thereby affecting the quality of coating and the consistency of performance, and the chemical bonding between stearic acid and coating is not strong enough, and the service life is low. Therefore, it is necessary to design a method for preparing aluminum alloy hydrophobic coating, in order to solve the problems of low service life, high cost and complicated preparation of aluminum alloy hydrophobic coating prepared in existing.

[0024] Reference Figure 1 As shown, in some embodiments of the present application, a method for preparing a super-hydrophobic coating on an aluminum alloy surface comprises:

[0025] Pretreatment: Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber and perform plasma treatment for 5-10 minutes;

[0026] Micro-arc oxidation: The pretreated aluminum alloy is used as the anode and fixed on the fixture of the micro-arc oxidation equipment. The stainless steel plate is used as the cathode and placed in the electrolytic cell filled with electrolyte. After adjusting the micro-arc oxidation process parameters, micro-arc oxidation begins.

[0027] Stearic acid modification: After the micro-arc oxidation is completed, the aluminum alloy sample after micro-arc oxidation is immersed in a stearic acid solution and stirred at a constant temperature of 60-80°C for 2-3 hours. The sample is then taken out, cleaned with ethanol and dried. After drying, a super-hydrophobic coating is obtained on the surface of the aluminum alloy.

[0028] In the pretreatment step of the present invention, the plasma treatment time is preferably 7-10 minutes, more preferably 10 minutes.

[0029] In the stearic acid modification step of the present invention, the constant temperature is preferably 70-80°C, more preferably 80°C;

[0030] In the stearic acid modification step of the present invention, the stirring time is preferably 3 hours.

[0031] It can be understood that the aluminum alloy is first subjected to micro-arc oxidation and then the aluminum alloy after micro-arc oxidation is modified with stearic acid, so that there is no need to add stearic acid solution to the electrolyte, thereby ensuring the consistency of the coating and improving the hydrophobicity of the coating; at the same time, by plasma treatment of the aluminum alloy, active sites are formed on the surface of the aluminum alloy, so that the stearic acid molecules and the micro-arc oxidation coating form a stronger chemical bond, thereby improving the bonding force between stearic acid and the coating, allowing stearic acid to be more firmly attached to the coating surface, reducing the shedding of stearic acid during use, and improving the hydrophobicity and durability of the coating.

[0032] In some embodiments of the present application, in the plasma treatment, argon gas is used as the working gas, the gas flow rate is controlled at 20-30 mL / min, the pressure in the chamber is maintained at 30-50 Pa; and the RF power is set to 100-150W.

[0033] It is understandable that plasma treatment can remove impurities such as oil stains and oxide layers on the surface of aluminum alloys. At the same time, through high-energy particle bombardment, a large number of free radicals and defects are generated on the surface to form active sites. These active sites can react chemically with functional groups such as carboxyl groups in stearic acid molecules to form stronger chemical bonds, thereby increasing the bonding force between stearic acid and the coating, allowing stearic acid to adhere more firmly to the coating surface, reducing the shedding of stearic acid during use, and improving the hydrophobic properties and durability of the coating.

[0034] In some embodiments of the present application, the electrolyte components in the micro-arc oxidation include: 100 parts of water, 10-15 parts of sodium silicate and 2-3 parts of sodium phosphate; preferably, 100 parts of water, 13-15 parts of sodium silicate and 3 parts of sodium phosphate; further preferably, 100 parts of water, 15 parts of sodium silicate and 3 parts of sodium phosphate.

[0035] It is understandable that the addition of sodium thiocarbate may change the chemical properties of the surface of the micro-arc oxidation coating and introduce more active sites or functional groups. These active sites can react chemically with functional groups such as carboxyl groups in the stearic acid molecules to form stronger chemical bonds, thereby increasing the binding force between stearic acid and the coating, allowing stearic acid to adhere more firmly to the coating surface, reducing the shedding of stearic acid during use, and improving the hydrophobic properties and durability of the coating.

[0036] In some embodiments of the present application, the preparation method of the electrolyte is: take 10-15 parts of sodium silicate and dissolve it in 100 parts of water, add potassium hydroxide (KOH) to adjust the pH value to 11-13, and add 2-3 parts of sodium phosphate and stir evenly to obtain the electrolyte.

[0037] It is understandable that in an alkaline environment, the concentration of hydroxide ions in the electrolyte is relatively high. For an electrolyte based on sodium silicate, hydroxide ions can promote the hydrolysis of sodium silicate and produce more silicate ions. These silicate ions participate in the formation of an oxide film on the surface of the aluminum alloy during the micro-arc oxidation process, which accelerates the growth rate of the oxide film and is conducive to the formation of a complete and continuous micro-arc oxidation coating.

[0038] It is understandable that an appropriate alkaline pH value helps to form a coating with a good pore structure. During the micro-arc oxidation process, the pore distribution of the coating generated under alkaline conditions is more reasonable and the pore size is more uniform. This pore structure can increase the specific surface area of ​​the coating and provide more active sites for the subsequent combination of stearic acid and the coating.

[0039] It is understandable that a large number of active groups such as hydroxyl groups are formed on the coating surface under the alkaline micro-arc oxidation environment. These active groups can undergo esterification reactions or other chemical bonding reactions with the carboxyl groups in the stearic acid molecules, thereby enhancing the bonding force between stearic acid and the coating. A higher pH value can activate the coating surface to a certain extent, making the subsequent stearic acid modification process more effective and improving the adsorption and bonding efficiency of stearic acid on the coating surface.

[0040] In some embodiments of the present application, the micro-arc oxidation process parameters are: voltage of 350-400V, pulse frequency of 500-800Hz, duty cycle of 20%-30% and treatment time of 10-15 minutes; preferably, voltage of 380-400V, pulse frequency of 600-800Hz, duty cycle of 30% and treatment time of 13-15 minutes; further preferably, voltage of 400V, pulse frequency of 800Hz, duty cycle of 30% and treatment time of 15 minutes.

[0041] In some embodiments of the present application, the stearic acid solution comprises: 100 parts of ethanol, 5-10 parts of stearic acid and 0.1-0.2 parts of a catalyst; preferably, 100 parts of ethanol, 10 parts of stearic acid and 0.2 parts of a catalyst.

[0042] In some embodiments of the present application, the catalyst is one of dibutyltin dilaurate, tetraisopropyl titanate and tetrabutyl zirconate, preferably dibutyltin dilaurate.

[0043] It is understood that dibutyltin dilaurate is an organic tin catalyst that catalyzes the reaction between stearic acid and active groups (such as hydroxyl groups) on the surface of the micro-arc oxidation coating. It can reduce the activation energy of the reaction, making it easier for stearic acid molecules to react chemically with active groups on the surface of the coating, such as esterification reactions.

[0044] It is understood that the catalyst helps to promote the formation of a stable chemical bond between stearic acid and the coating. Through the catalytic effect, the carboxyl groups in the stearic acid molecules and the hydroxyl groups on the coating surface undergo a more effective condensation reaction to form an ester bond, thereby enhancing the bonding force between stearic acid and the coating, allowing the stearic acid to adhere more firmly to the coating surface.

[0045] It can be understood that dibutyltin dilaurate can guide the reaction toward the direction of generating the target product (ie, the product of chemical bonding of stearic acid to the coating surface).

[0046] In some embodiments of the present application, the drying temperature in the stearic acid modification is 80-100°C, and the drying time is 1-2 hours; the drying temperature is preferably 80-100°C, and the drying time is preferably 2 hours.

[0047] Example 1

[0048] S1. Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber; introduce argon (Ar) as the working gas, the gas flow rate is controlled at 20 mL / min, and the pressure in the chamber is maintained at 30 Pa; the radio frequency power is set to 100 W, and the treatment time is 5 minutes;

[0049] S2, dissolving 10 parts of sodium silicate in 100 parts of deionized water, adding potassium hydroxide (KOH) to adjust the pH value to 11-13, and adding 2 parts of sodium phosphate and stirring evenly to obtain an electrolyte;

[0050] S3, the pretreated aluminum alloy is used as an anode, fixed on the fixture of the micro-arc oxidation equipment, and the stainless steel plate is used as a cathode, and placed in an electrolytic cell filled with electrolyte, and the micro-arc oxidation process parameters are adjusted, specifically, the voltage is 350V, the pulse frequency is 500Hz, and the duty cycle is 20%, and then the micro-arc oxidation is performed for 10 minutes;

[0051] S4, dissolving 5 parts of stearic acid in 100 parts of ethanol solution, and then adding 0.1 parts of dibutyltin dilaurate to prepare a stearic acid solution;

[0052] S5. Immerse the aluminum alloy sample after micro-arc oxidation in a stearic acid solution, stir it at a constant temperature at 60°C for 2 hours, then take out the sample, clean it with ethanol, and dry it in a vacuum drying oven at 80°C for 1 hour to obtain a super-hydrophobic coating on the aluminum alloy surface.

[0053] Example 2

[0054] S1. Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber; introduce argon (Ar) as the working gas, the gas flow rate is controlled at 30 mL / min, and the pressure in the chamber is maintained at 50 Pa; the radio frequency power is set to 130 W, and the treatment time is 8 minutes;

[0055] S2, dissolving 13 parts of sodium silicate into 100 parts of deionized water, adding potassium hydroxide (KOH) to adjust the pH value to 11-13, and adding 3 parts of sodium phosphate and stirring evenly to obtain an electrolyte;

[0056] S3, the pretreated aluminum alloy is used as an anode, fixed on the fixture of the micro-arc oxidation equipment, and the stainless steel plate is used as a cathode, and placed in an electrolytic cell filled with electrolyte, and the micro-arc oxidation process parameters are adjusted, specifically, the voltage is 380V, the pulse frequency is 600Hz, and the duty cycle is 30%, and then the micro-arc oxidation is performed for 13 minutes;

[0057] S4, dissolving 8 parts of stearic acid in 100 parts of ethanol solution, and then adding 0.2 parts of dibutyltin dilaurate to prepare a stearic acid solution;

[0058] S5. The aluminum alloy sample after micro-arc oxidation was immersed in a stearic acid solution, stirred at a constant temperature of 70°C for 3 hours, and then the sample was taken out, cleaned with ethanol, and dried in a vacuum drying oven at 90°C for 2 hours to obtain a super-hydrophobic coating on the aluminum alloy surface.

[0059] Example 3

[0060] S1. Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber; introduce argon (Ar) as the working gas, the gas flow rate is controlled at 30 mL / min, and the pressure in the chamber is maintained at 50 Pa; the radio frequency power is set to 150 W, and the treatment time is 10 minutes;

[0061] S2, dissolving 15 parts of sodium silicate in 100 parts of deionized water, adding potassium hydroxide (KOH) to adjust the pH value to 11-13, and adding 3 parts of sodium phosphate and stirring evenly to obtain an electrolyte;

[0062] S3, the pretreated aluminum alloy is used as an anode, fixed on the fixture of the micro-arc oxidation equipment, and the stainless steel plate is used as a cathode, and placed in an electrolytic cell filled with electrolyte, and the micro-arc oxidation process parameters are adjusted, specifically, the voltage is 400V, the pulse frequency is 800Hz, and the duty cycle is 30%, and then the micro-arc oxidation is performed for 15 minutes;

[0063] S4, dissolving 10 parts of stearic acid in 100 parts of ethanol solution, and then adding 0.2 parts of dibutyltin dilaurate to prepare a stearic acid solution;

[0064] S5. Immerse the aluminum alloy sample after micro-arc oxidation in a stearic acid solution, stir it at a constant temperature of 80°C for 3 hours, then take out the sample, clean it with ethanol, and dry it in a vacuum drying oven at 100°C for 2 hours to obtain a super-hydrophobic coating on the aluminum alloy surface.

[0065] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0066] The present application is described with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0067] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0068] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a super-hydrophobic coating on an aluminum alloy surface, characterized in that: include: Pretreatment: Use a radio frequency plasma generator to place the aluminum alloy sample in a plasma reaction chamber and perform plasma treatment for 5-10 minutes; Micro-arc oxidation: The pretreated aluminum alloy is used as the anode and fixed on the fixture of the micro-arc oxidation equipment. The stainless steel plate is used as the cathode and placed in the electrolytic cell filled with electrolyte. After adjusting the micro-arc oxidation process parameters, micro-arc oxidation begins. Stearic acid modification: After the micro-arc oxidation is completed, the aluminum alloy sample after micro-arc oxidation is immersed in a stearic acid solution and stirred at a constant temperature of 60-80°C for 2-3 hours. The sample is then taken out, cleaned with ethanol and dried. After drying, a super-hydrophobic coating is obtained on the surface of the aluminum alloy.

2. The method for preparing a super-hydrophobic coating on an aluminum alloy surface according to claim 1, wherein In the plasma treatment, argon gas is used as the working gas, the gas flow rate is controlled at 20-30 mL / min, the pressure in the chamber is maintained at 30-50 Pa; and the radio frequency power is set to 100-150 W.

3. The method for preparing super-hydrophobic coating on aluminum alloy surface according to claim 1, wherein The electrolyte components in the micro-arc oxidation include: 100 parts of water, 10-15 parts of sodium silicate and 2-3 parts of sodium phosphate.

4. The method for preparing a micro-arc oxidation heat-absorbing coating according to claim 3, characterized in that: The preparation method of the electrolyte is as follows: 10-15 parts of sodium silicate are dissolved in 100 parts of water, potassium hydroxide (KOH) is added to adjust the pH value to 11-13, and 2-3 parts of sodium phosphate are added and stirred evenly to obtain the electrolyte.

5. The method for preparing super-hydrophobic coating on aluminum alloy surface according to claim 1, wherein The micro-arc oxidation process parameters are: voltage of 350-400V, pulse frequency of 500-800Hz, duty cycle of 20%-30% and processing time of 10-15 minutes.

6. The method for preparing a super-hydrophobic coating on an aluminum alloy surface according to claim 1, wherein The stearic acid solution comprises: 100 parts of ethanol, 5-10 parts of stearic acid and 0.1-0.2 parts of a catalyst.

7. The method for preparing a super-hydrophobic coating on an aluminum alloy surface according to claim 6, wherein: The catalyst is one of dibutyltin dilaurate, tetraisopropyl titanate and tetrabutyl zirconate.

8. The method for preparing a super-hydrophobic coating on an aluminum alloy surface according to claim 1, wherein The drying temperature in the stearic acid modification is 80-100° C., and the drying time is 1-2 hours.

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