A super-hydrophobic coating, its preparation method and use

Abstract

The application discloses a super-hydrophobic coating and a preparation method and application thereof, and belongs to the technical field of functional coating materials. The super-hydrophobic coating is prepared by using a hydrophilic epoxy resin and a hydrophilic fumed silica as main raw materials, utilizing ring-opening reaction of epoxy groups and silicon hydroxyl groups on the surface of the silica, and combining curing and film forming to construct a micro-nano composite rough structure, so that the super-hydrophobic coating is obtained. The super-hydrophobic coating and the preparation method thereof are adopted, the raw material ratio and the reaction temperature are regulated, the water static contact angle of the coating is continuously adjustable, the super-hydrophobic effect is realized by means of the interface chemical reaction of the raw materials and the micro rough structure, the obtained super-hydrophobic coating has good self-cleaning performance, is resistant to washing and abrasion, and has good mechanical stability. The raw materials are green and environmentally friendly, easy to obtain, and simple in process, the production cost is greatly reduced, the scale spraying production is facilitated, and the super-hydrophobic coating can be widely applied to the fields of antifouling, corrosion prevention and self-cleaning protection of glass, metal or concrete substrates.

Description

Technical Field

[0001] This invention relates to the field of functional coating materials technology, and in particular to a superhydrophobic coating, its preparation method, and its application. Background Technology

[0002] Superhydrophobic surfaces, with their high static contact angle and low roll-off angle, enable water droplets to roll off in a spherical shape. They have broad application prospects in many fields such as material self-cleaning, anti-icing, anti-corrosion and rust prevention, and microfluidic devices. Applying superhydrophobic properties to the surfaces of various substrates such as glass, metal, and concrete in the form of coatings is one of the important ways to realize the large-scale application of superhydrophobic technology.

[0003] Currently, the industry generally follows the technical approach of "constructing micro-nano rough structures + low surface energy chemical modification" to prepare superhydrophobic coatings. On the one hand, hierarchical rough morphology is constructed through filler agglomeration, substrate etching, and spraying to retain air at the solid-liquid interface; on the other hand, modifying agents such as perfluorinated organic compounds and long-chain alkylsilanes are used to reduce the surface free energy of the coating, thereby obtaining a superhydrophobic coating that meets the specifications. Most existing technologies use hydrophobically modified fumed silica combined with silane coupling agents, fluorinated hydrophobic agents, and epoxy resin to prepare superhydrophobic coatings. However, this type of existing preparation process has obvious drawbacks: fluorinated modifying agents have poor biodegradability, posing ecological and health risks; long-chain alkylsilane additives not only increase the raw material production cost, but also easily release volatile organic pollutants during the formulation and application stages; to improve the interfacial compatibility between hydrophilic silica and epoxy resin, existing solutions also require the addition of coupling agents or prior hydrophobic modification of silica, resulting in complex formulation components and increased preparation steps, making it difficult to balance green production and product performance. In addition, if the wettability of existing coatings needs to be adjusted, it is usually necessary to change to different types of hydrophobic modifiers or to perform post-modification treatment on the finished coating. The adjustable range of the wetting range by relying on process parameters is narrow, which is not conducive to the uniform control of performance in the mass production process.

[0004] In summary, existing superhydrophobic coating preparation technologies generally suffer from drawbacks such as poor environmental friendliness of raw materials, cumbersome formulations, high production costs, and limited methods for controlling wettability. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a superhydrophobic coating and its preparation method. Without using organic fluorine compounds or introducing additional alkylsilane hydrophobic modifiers, a micro-nano composite rough structure is constructed by reacting and combining hydrophilic epoxy resin with the hydroxyl groups on the surface of hydrophilic fumed silica to form a film, thereby obtaining a superhydrophobic coating.

[0006] To achieve the above objectives, the present invention provides a method for preparing a superhydrophobic coating, comprising the following steps: S1. Add fumed silica to ethanol and disperse it by ultrasonication to obtain a silica-ethanol dispersion; S2. Add epoxy resin to the silica ethanol dispersion and stir and react to obtain a mixed coating of epoxy resin and silica. S3. Add the amine curing agent to the epoxy resin and silica mixed coating, stir, and obtain a sprayable superhydrophobic coating. S4. Spray the superhydrophobic coating onto the substrate surface and cool it to obtain a superhydrophobic coating.

[0007] Preferably, in S1, the mass-to-volume ratio of fumed silica to ethanol is 1g:30mL, the ultrasonic dispersion time is >20min, and the particle size of fumed silica is 20nm.

[0008] Preferably, in S2, the mass ratio of epoxy resin to fumed silica is 1:1-2, and the epoxy resin is selected from bisphenol A type epoxy resin, including epoxy resin E-51.

[0009] Furthermore, the mass ratio of epoxy resin to fumed silica is 1:2 or 1:1.

[0010] Preferably, in S2, the reaction temperature is 25-30℃ and the reaction time is 2h.

[0011] Preferably, in S3, the amine curing agent includes ethylenediamine.

[0012] Preferably, in S3, the mass ratio of amine curing agent to epoxy resin is 0.4-0.6:1, and the stirring time is 5-15 min.

[0013] Preferably, in S4, the substrate includes glass, metal, or concrete, and the spraying adopts a two-stage pressure process: in the first stage, the spraying pressure is 0.2-0.4 MPa, the distance between the spray gun and the substrate is 20-40 cm, the number of sprays is 1-3, the curing temperature is 60-80℃, and the curing time is 1-2 h; in the second stage, the spraying pressure is 0.5-0.8 MPa, the distance between the spray gun and the substrate is 20-40 cm, the number of sprays is 1-3, the curing temperature is 60-80℃, and the curing time is 1-2 h.

[0014] The present invention also provides a superhydrophobic coating, which is prepared by the above-described preparation method.

[0015] The present invention also provides an application of a superhydrophobic coating, which is used for antifouling, anti-corrosion and self-cleaning protection of glass, metal or concrete substrates.

[0016] The preparation principle and wettability changes of the superhydrophobic coating of this invention are as follows: Figure 1As shown, the ring-opening reaction between the epoxy groups of hydrophilic epoxy resin and the silanol groups on the surface of hydrophilic fumed silica forms a chemical anchor on the particle surface, promoting the coating and fixation of silica by epoxy resin and enhancing the organic-inorganic interface bonding. On the one hand, this reaction consumes the hydroxyl groups on the surface of fumed silica, gradually transforming the film interface from a state dominated by highly polar silanol exposure to a state of organic coating, thereby causing the coating to change from a hydrophilic to a hydrophobic tendency, which, together with the subsequent roughening structure, supports the superhydrophobic appearance. On the other hand, the nanoparticles provided by fumed silica have a high specific surface area, which can induce the epoxy resin to rearrange and oriented on the nanoparticle surface: hydrophilic polar groups are more likely to face towards the particle interface and be anchored or embedded in the particle-resin interface region, while hydrophobic segments / groups are more likely to extend outward and accumulate on the outer surface, forming a nanoscale orientation trend of "hydrophilic groups inward and hydrophobic groups outward," further enhancing the hydrophobicity and low adhesion characteristics of the coating. Ethanol is used to disperse fumed silica and to dissolve / swell epoxy resin, ensuring the system remains uniform and workable before spraying. It also helps control slurry viscosity and spray rheology, facilitating stable film formation. Spray deposition creates a hierarchical rough structure composed of micron-scale protrusions and surface nanoscale particles, which facilitates gas retention at the solid-liquid interface, providing a structural basis for superhydrophobicity. Amine-based curing agents initiate cross-linking of the epoxy resin to form a three-dimensional network, maintaining the integrity and stability of the film structure.

[0017] Building upon the above, this invention further regulates the wettability of the coating (e.g., the static contact angle with water) by controlling key process parameters during the preparation process. Preferably, by altering the reaction temperature during the interaction stage between the epoxy resin and fumed silica, the epoxy-hydroxyl reaction rate, coating integrity, and aggregate morphology are controlled. This simultaneously changes the degree of hydroxyl group consumption, the rearrangement / orientation state of the epoxy resin on the nanoparticle surface, the hierarchical structural scale, and the surface chemical exposure ratio, thus achieving adjustable wettability.

[0018] Therefore, the present invention employs the above-mentioned superhydrophobic coating and its preparation method, which has the following beneficial effects: (1) Green and environmentally friendly, with a simplified formula: The superhydrophobic coating of this invention does not use organic fluorine compounds and does not introduce additional alkyl silane hydrophobic modifiers, thus avoiding the problem of difficult degradation of fluorine-containing raw materials, reducing the pre-hydrophobic modification process of silica, and resulting in fewer types of raw materials and a simple and green formula composition.

[0019] (2) Obtaining superhydrophobic apparent properties from hydrophilic components: In this invention, a superhydrophobic coating is prepared without the addition of hydrophobic agents in a system with hydrophilic epoxy resin and hydrophilic fumed silica as the main materials, through the interfacial reaction between epoxy groups and hydroxyl groups on the surface of silica, combined with the micro-nano hierarchical rough structure constructed by spraying. This breaks through the conventional thinking of relying on raw material selection and modification.

[0020] (3) The wetting performance of the superhydrophobic coating is adjustable: The present invention can flexibly change the static water contact angle of the coating by adjusting the ratio of epoxy resin to fumed silica, reaction temperature and other process parameters, and adjust the hydrophobic performance as needed. It can adapt to different working conditions without changing the modified additives, and the process control is flexible.

[0021] (4) The preparation process is suitable for large-scale coating: The present invention uses ethanol as the dispersion medium and adopts a spray coating process to form a film. The raw materials are easy to obtain and the process is simple. Furthermore, by controlling the atomization effect and deposition level through segmented spraying pressure, it helps to stably prepare coatings on large-area or batch substrates. It can be widely used in the fields of antifouling, anti-corrosion and self-cleaning protection of substrates such as glass.

[0022] (5) Excellent mechanical and durability properties of the coating: In this invention, the epoxy resin is cured and cross-linked to form a dense organic network, which firmly anchors the silica particles inside the coating. The coating has excellent adhesion to the substrate. After rain erosion and wear resistance test, the hydrophobicity decreases by a small margin. It has excellent wear resistance and erosion resistance, which can extend the service life.

[0023] (6) Cost advantage: This invention eliminates expensive fluorinated reagents, modified silanes, coupling agents and other additives, shortens the pretreatment process, significantly reduces the overall procurement and processing costs of raw and auxiliary materials, and gives the product outstanding market cost competitiveness.

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation principle and wettability change of the superhydrophobic coating in Example 1 of the present invention; Figure 2 This is a graph showing the changes in wettability of the coatings obtained at different reaction temperatures in Example 1 and Comparative Examples 1-4 of the present invention; Figure 3 This is a graph showing the change in wettability of coatings obtained under different mass ratios of epoxy resin and fumed silica in Examples 1-2 and Comparative Examples 5-8 of the present invention. Figure 4 These are scanning electron microscope (SEM) characterization images of the coatings of Comparative Example 5, Example 1, and Comparative Example 8 of the present invention; Figure 5This refers to the self-cleaning performance of the superhydrophobic coating prepared in Example 1 of this invention; Figure 6 This is a graph showing the change of the static water contact angle of the superhydrophobic coating prepared in Example 1 of the present invention during rainwater scouring and abrasion resistance tests. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] In this invention, the CAS number of fumed silica is 112945-52-5, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; the CAS number of epoxy resin E-51 is 61788-97-4, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; other test materials and instruments are all conventional test materials in the field and can be purchased through commercial channels.

[0029] Example 1 A method for preparing a superhydrophobic coating includes the following steps: S1. Add 1g of fumed silica (particle size 20nm) to 30mL of anhydrous ethanol and ultrasonically disperse for 30min to obtain silica ethanol dispersion. S2. Add 0.5g of epoxy resin E51 to the silica ethanol dispersion, react at a temperature of 25℃, and stir continuously for 2h under magnetic stirring to obtain a mixed coating of epoxy resin and silica. S3. Add 0.3g of ethylenediamine to the epoxy resin and silica mixed coating, stir for 10 minutes to mix evenly, and obtain a sprayable superhydrophobic coating. S4. Apply the superhydrophobic coating to a clean glass substrate surface using a two-stage pressure process: The first stage spraying pressure is 0.3 MPa, the distance between the spray gun and the substrate is 30 cm, and 1-3 coats are applied until the wet film is uniform, then cured at 70℃ for 1.5 h; After the first layer is fully cured, the second stage spraying pressure is increased to 0.6 MPa, the distance between the spray gun and the substrate is 30 cm, and 1-3 coats are applied, then cured at 70℃ for 1.5 h; then cool to room temperature to obtain the superhydrophobic coating.

[0030] Example 2 This embodiment operates in the same way as Example 1, except that in S2, the amount of epoxy resin added is 1g; and in S3, the amount of ethylenediamine added is 0.5g.

[0031] Comparative Example 1 The operation of this comparative example is the same as that of Example 1, except that in S2, the reaction temperature is 35°C; and in S4, a coating is obtained.

[0032] Comparative Example 2 The operation of this comparative example is the same as that of Example 1, except that in S2, the reaction temperature is 45°C; and in S4, a coating is obtained.

[0033] Comparative Example 3 This comparative example operates in the same manner as Example 1, except that in S2, the reaction temperature is 55°C; and in S4, a coating is obtained.

[0034] Comparative Example 4 The operation of this comparative example is the same as that of Example 1, except that in S2, the reaction temperature is 65°C; and in S4, a coating is obtained.

[0035] Comparative Example 5 The operation of this comparative example is the same as that of Example 1, except that: in S2, the amount of epoxy resin added is 0.1g; in S3, the amount of ethylenediamine added is 0.05g; and in S4, a coating is obtained.

[0036] Comparative Example 6 The comparative example operates in the same manner as Example 1, except that: in S2, the amount of epoxy resin added is 0.2g; in S3, the amount of ethylenediamine added is 0.1g; and in S4, a coating is obtained.

[0037] Comparative Example 7 The comparative example operates in the same manner as Example 1, except that: in S2, the amount of epoxy resin added is 2g; in S3, the amount of ethylenediamine added is 1g; and in S4, a coating is obtained.

[0038] Comparative Example 8 The operation of this comparative example is the same as that of Example 1, except that: in S2, the amount of epoxy resin added is 4g; in S3, the amount of ethylenediamine added is 2g; and in S4, a coating is obtained.

[0039] The wettability of the superhydrophobic coatings prepared in Examples 1-2 and the coatings prepared in Comparative Examples 1-8 was tested using a contact angle meter (measurements were taken at least at 5 points on each of at least two independent samples). The results are as follows: Figure 2 and Figure 3 As shown. Among them, Figure 2 This is a graph showing the changes in wettability of the coatings obtained at different reaction temperatures in Example 1 and Comparative Examples 1-4. Figure 3 The diagram shows the changes in wettability of coatings obtained under different mass ratios of epoxy resin and fumed silica in Examples 1-2 and Comparative Examples 5-8.

[0040] from Figure 2As can be seen, the static water contact angle of the superhydrophobic coating in Example 1 (25℃) is 153°, while the static water contact angles of the coatings in Comparative Examples 1-4 (reaction temperatures of 35℃, 45℃, 55℃, and 65℃, respectively) are 141°, 132°, 118°, and 103°. When the reaction temperature exceeds 30℃, the interfacial reaction kinetics accelerate sharply, disrupting the conditions for superhydrophobicity formation from both the chemical interface and microstructure perspectives, resulting in a contact angle below 150°, thus failing to achieve superhydrophobicity. This also indicates that controlling the reaction temperature between epoxy resin and fumed silica can alter the degree of interfacial reaction and the resin's coating state on the filler surface, thereby achieving continuously adjustable coating wettability.

[0041] from Figure 3 As can be seen, the static water contact angles of the superhydrophobic coatings in Examples 1-2 were 153° and 151°, respectively, while the static water contact angles of the coatings in Comparative Examples 5-8 were 8°, 23°, 139°, and 92°, respectively. When the proportion of fumed silica was too high, the epoxy resin could not fully coat the particles, and a large number of hydrophilic silanol groups were exposed, resulting in a low coating contact angle. When the ratio of the two reached the optimal value (1:2, i.e., Example 1), the coating contact angle reached its peak, achieving a superhydrophobic effect. When the epoxy resin was added in excess, the nano-silica was completely coated by the epoxy resin, the micro-rough structure of the coating disappeared, and the hydrophobicity decreased significantly.

[0042] The morphology of the coatings in Comparative Example 5, Example 1, and Comparative Example 8 was characterized using scanning electron microscopy (SEM), and the results are as follows: Figure 4 As shown, where, Figure 4 In the figure, 'a' is the SEM image of Comparative Example 5. Figure 4 In the image, b is the SEM characterization image of Example 1. Figure 4 In the diagram, 'c' represents the SEM image of Comparative Example 8. From... Figure 4 As can be seen, the coating sample of Comparative Example 5 (epoxy resin to fumed silica mass ratio of 1:10) has exposed powder particles and disordered micropores on its surface. The superhydrophobic coating sample of Example 1 (epoxy resin to fumed silica mass ratio of 1:2) forms a hierarchical rough structure with micron-sized aggregates and surface nano-protrusions. The coating sample of Comparative Example 8 (epoxy resin to fumed silica mass ratio of 4:1) has particles buried by epoxy resin, and the surface tends to be smooth overall. This explains the intrinsic mechanism of the change in wetting properties by the raw material ratio at the microstructural level.

[0043] Using carbon black as the contaminant, the self-cleaning performance of the superhydrophobic coating prepared in Example 1 was verified through the following experiments: (1) Pollution load: Carbon black particles were uniformly loaded on the surface of the superhydrophobic coating sample prepared in Example 1 as model pollutants; at the same time, glass slides without superhydrophobic coating were used as control samples; (2) Tilting and rolling self-cleaning: Place the superhydrophobic coating sample loaded with carbon black on a carrier such as a petri dish and fix it at an angle of 10°. Add or guide water droplets to the coating surface so that the water droplets form a spherical shape and roll off the coating surface. Record the amount of carbon black carried away during the rolling of the water droplets. Repeat the rolling several times until the coating surface is visually clean. Observe whether the water droplets can maintain low adhesion and roll off the coating surface. (3) Preparation of pollutant slurry: Mix carbon black with water to prepare pollutant slurry (simulating outdoor mud / particulate dispersion pollution), and stir evenly for later use.

[0044] (4) Immersion Cycle Antifouling Comparison: Uncoated glass slides and coated samples were immersed in the contaminated slurry, respectively; after removal, the degree of residual contamination on the surface was observed. Uncoated samples should have full contact with the slurry and obvious adhesion of sludge; coated samples should form a stable air cushion layer between the coating and the slurry and reduce the contact area and adhesion. The coated samples were repeatedly immersed and removed for no less than 20 cycles to confirm that the surface could still repel the slurry and remain relatively clean; the antifouling performance of the coating and its potential for outdoor application were evaluated accordingly.

[0045] The results are as follows Figure 5 As shown, where, Figure 5 (a1), (a2), and (a3) ​​are schematic diagrams of water droplets rolling off the surface of the superhydrophobic coating sample of Example 1, which is tilted at a 10° angle and loaded with carbon black pollutants, at different time periods. (b1), (b2), and (b3) are physical images of water droplets rolling off the surface of the superhydrophobic coating sample of Example 1, which is tilted at a 10° angle and loaded with carbon black pollutants, at different time periods. (c1) is a schematic diagram of a glass slide without superhydrophobic coating in contact with pollutants. (c2) is a schematic diagram of a glass slide coated with the superhydrophobic coating of Example 1 in contact with pollutants. (d1) is a physical image of a glass slide without superhydrophobic coating in contact with pollutants. (d2) is a physical image of a glass slide coated with the superhydrophobic coating of Example 1 in contact with pollutants.

[0046] from Figure 5 As shown in (a1), (a2), (a3), (b1), (b2), and (b3), after loading carbon black contaminants, water droplets placed at a 10° angle on the surface of the superhydrophobic coating can maintain a complete spherical shape. During the rolling process, the water droplets can efficiently entrain and carry away the carbon black particles on the surface. After several rounds of water droplet rolling and rinsing, the carbon black contaminants on the coating surface are basically removed, restoring the surface to a clean state. In contrast, the uncoated glass control sample shows water droplets spreading and adhering to the substrate, unable to remove carbon black impurities through rolling. This demonstrates that the superhydrophobic coating possesses excellent self-cleaning properties.

[0047] from Figure 5As shown in (c1), (c2), (d1), and (d2), when immersion antifouling tests were conducted using carbon black slurry to simulate outdoor mud pollution, the glass without the superhydrophobic coating showed a large amount of carbon black stains adhering to its surface after immersion in the slurry, indicating severe contamination. The superhydrophobic coating, however, formed a stable air cushion layer, reducing the solid-liquid contact area and significantly decreasing slurry adhesion. After a single immersion and removal cycle, virtually no contaminants remained on the surface. Even after at least 20 immersion-removal cycles, the coating still stably repelled the contaminated slurry, with no obvious contaminant accumulation on the surface, demonstrating stable long-term antifouling performance. This fully illustrates the excellent antifouling durability of the superhydrophobic coating and its promising potential for practical outdoor applications.

[0048] The superhydrophobic coating prepared in Example 1 was subjected to rain erosion resistance test and Taber abrasion test to verify the mechanical stability of the superhydrophobic coating: (1) Rainwater scouring test: The rainwater scouring resistance was verified by a scouring device. The diameter of the scouring nozzle was 2 mm and the flow rate of the scouring water was 5 m / s. The superhydrophobic coating sample prepared in Example 1 was placed under the scouring condition for rinsing. After scouring, the sample was thoroughly dried and the static water contact angle of the coating was measured by a contact angle measuring instrument. (2) Taber wear resistance test: The wear resistance test was conducted using a Taber wear resistance tester. The superhydrophobic coating sample prepared in Example 1 was fixed on a rotating platform and rubbed against the sample surface under the condition of friction wheel load. The surface of the friction wheel was covered with 2000-grit sandpaper. The wear test was conducted under a 5N load. After the test, the static contact angle of water was measured using a contact angle measuring instrument.

[0049] The results are as follows Figure 6 As shown, where, Figure 6 In the graph, 'a' represents the change in the static contact angle of water during the wear resistance test. Figure 6 In the diagram, b represents the change in the static contact angle of water during the rainwater scouring experiment.

[0050] from Figure 6 As can be seen from the results, after prolonged rain erosion and multiple abrasion tests, the static water contact angle of the superhydrophobic coating prepared in Example 1 only decreased slightly, and the overall level of hydrophobicity was still maintained. This indicates that the resin matrix formed by cross-linking epoxy resin in this invention can firmly anchor silica particles, and the coating has outstanding mechanical stability and durability, making it practically valuable for long-term outdoor use.

[0051] Therefore, this invention employs the aforementioned superhydrophobic coating and its preparation method. By controlling the raw material ratio and reaction temperature, the static water contact angle of the coating can be continuously adjusted. The superhydrophobic effect is achieved through the synergistic effect of the interfacial chemical reaction of the raw materials and the microscopic rough structure. The resulting superhydrophobic coating exhibits excellent self-cleaning properties, erosion and wear resistance, and good mechanical stability. The raw materials used in this invention are environmentally friendly, readily available, and the process is simple, significantly reducing production costs and facilitating large-scale spray coating production. It can be widely applied in the fields of antifouling, anti-corrosion, and self-cleaning protection of glass substrates.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a superhydrophobic coating, characterized in that: Includes the following steps: S1. Add fumed silica to ethanol and disperse it by ultrasonication to obtain a silica-ethanol dispersion; S2. Add epoxy resin to silica ethanol dispersion and stir and react to obtain epoxy resin and silica mixed coating; S3. Add the amine curing agent to the epoxy resin and silica mixed coating, stir, and obtain a sprayable superhydrophobic coating. S4. Spray the superhydrophobic coating onto the substrate surface and cool it to obtain a superhydrophobic coating.

2. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S1, the mass-to-volume ratio of fumed silica to ethanol is 1 g: 30 mL, the ultrasonic dispersion time is >20 min, and the particle size of fumed silica is 20 nm.

3. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S2, the mass ratio of epoxy resin to fumed silica is 1:1-2, and the epoxy resin is selected from bisphenol A type epoxy resin, including epoxy resin E-51.

4. The method for preparing a superhydrophobic coating according to claim 3, characterized in that: The mass ratio of epoxy resin to fumed silica is 1:2 or 1:

1.

5. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S2, the reaction temperature is 25-30℃ and the reaction time is 2h.

6. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S3, the amine curing agent includes ethylenediamine.

7. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S3, the mass ratio of amine curing agent to epoxy resin is 0.4-0.6:1, and the stirring time is 5-15 minutes.

8. The method for preparing a superhydrophobic coating according to claim 1, characterized in that: In S4, the substrate includes glass, metal, or concrete. The spraying process uses a two-stage pressure process: In the first stage, the spraying pressure is 0.2-0.4 MPa, the distance between the spray gun and the substrate is 20-40 cm, the number of sprays is 1-3, the curing temperature is 60-80℃, and the curing time is 1-2 hours; In the second stage, the spraying pressure is 0.5-0.8 MPa, the distance between the spray gun and the substrate is 20-40 cm, the number of sprays is 1-3, the curing temperature is 60-80℃, and the curing time is 1-2 hours.

9. A superhydrophobic coating, characterized in that: The superhydrophobic coating was prepared using the method described in any one of claims 1-8.

10. An application of a superhydrophobic coating, characterized in that: The superhydrophobic coating of claim 9 is used for antifouling, anticorrosion and self-cleaning protection of glass, metal or concrete substrates.

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