Preparation method of biomimetic expanded graphite super-hydrophobic material and super-hydrophobic composite coating

Abstract

The present invention discloses a preparation method of a bionic expanded graphite superhydrophobic material and a superhydrophobic composite coating. The preparation method is as follows: expanded graphite and nano-zirconia are added to ultrapure water and stirred and mixed to obtain a mixed dispersion A; dopamine hydrochloride and tris(hydroxymethyl)aminomethane are added to the mixed dispersion A, and after the reaction is completed, centrifugation is carried out to separate out a solid product; the solid product is washed with absolute ethanol and then dried to obtain a P-ZrO2@EG material; the P-ZrO2@EG material is dispersed in absolute ethanol, and 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-tridecafluorodecyltriethoxysilane is added and mixed evenly to obtain a mixed dispersion B; the solid obtained after centrifuging the mixed dispersion B is washed with absolute ethanol and vacuum dried to obtain the bionic expanded graphite superhydrophobic material. The material is sprayed onto a semi-cured epoxy resin primer and cured to obtain the superhydrophobic composite coating. The present invention can solve the problem of poor long-term anti-corrosion performance of existing superhydrophobic anti-corrosion coatings.

Description

Technical Field

[0001] The invention relates to the technical field of super hydrophobic coatings, and specifically relates to a preparation method of a biomimetic expanded graphite super hydrophobic material and a super hydrophobic composite coating. Background Art

[0002] Metal corrosion occurs widely in various fields such as social production and life. In order to prevent metal from being corroded, one of the most effective methods is to form a protective film on the surface of the metal substrate, which can effectively isolate the intrusion of the corrosive medium, thereby preventing the corrosive ions from directly invading the metal surface. However, single-component polymer coatings such as epoxy resins and polyurethanes, especially epoxy resin coating surfaces, are hydrophilic, and it is easy for the corrosive medium to pass through the coating to reach the metal surface, and corrosion reactions occur at the interface between the metal and the coating, which makes it difficult to achieve long-term effective protection for the metal substrate; in addition, there are defects such as micropores and cracks in the coating surface, which provide diffusion pathways for some corrosive ions in the environment, resulting in metal being corroded. Introducing anticorrosive coatings with super-hydrophobic surfaces has become a new development path that inevitably leads to the penetration of corrosive ions. However, super-hydrophobic coatings still have the following disadvantages: when exposed to the working environment, the stability of the coating decreases rapidly due to mechanical forces, corrosion of chemical components, etc., and the anticorrosion performance is reduced, and its own anticorrosion performance also needs to be further improved. Summary of the invention

[0003] To this end, the technical problem to be solved by the present invention is to provide a preparation method of a bionic expanded graphite super-hydrophobic material and a super-hydrophobic composite coating to solve the problem of poor long-term anti-corrosion performance of existing super-hydrophobic anti-corrosion coatings.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] The preparation method of biomimetic expanded graphite super-hydrophobic material comprises the following steps:

[0006] Step A, adding expanded graphite and nano zirconium dioxide into ultrapure water and stirring and mixing to obtain a mixed dispersion A;

[0007] Step B, adding dopamine hydrochloride and tris(hydroxymethyl)aminomethane to the mixed dispersion A, mixing and stirring to react; after the reaction is completed, centrifugation is performed to obtain a solid product;

[0008] Step C: washing the solid product with anhydrous ethanol and drying it to obtain P-ZrO 2 @EG Materials;

[0009] Step D: P-ZrO 2@EG material was redispersed in anhydrous ethanol, and tridecafluorooctyl triethoxysilane was added and stirred to mix evenly to obtain a mixed dispersion B;

[0010] Step E: washing the solid obtained after centrifugation of the mixed dispersion B with anhydrous ethanol, and then drying it in a vacuum drying oven. After drying, a bionic expanded graphite super-hydrophobic material is obtained.

[0011] The preparation method of the bionic expanded graphite super-hydrophobic material comprises the following steps: in step A, the mass ratio of expanded graphite to nano zirconium dioxide is 1:2; the concentration of expanded graphite in the mixed dispersion A is 2.5-3.0wt%; the expanded graphite is sieved through a 200-mesh sieve (an expanded graphite particle size that is too large will affect the hydrophobicity of the coating, and when it contacts water droplets, there is a large gap, and the air layer on the surface of the coating is easily destroyed); and the particle size of the nano zirconium dioxide is less than or equal to 100nm.

[0012] In the preparation method of the biomimetic expanded graphite super-hydrophobic material, in step B, the mass ratio of dopamine hydrochloride to tris(hydroxymethyl)aminomethane is 1:1, the mass ratio of dopamine hydrochloride to expanded graphite is 1:15-16; and the stirring reaction time is 5-8 hours.

[0013] In the preparation method of the biomimetic expanded graphite super-hydrophobic material, in step C, the drying temperature is 55 to 65° C., and the drying time is 10 to 12 hours.

[0014] The preparation method of the biomimetic expanded graphite super-hydrophobic material, in step D, anhydrous ethanol and P-ZrO 2 @The volume-to-mass ratio of the EG material is 15-20 mL / g; the volume ratio of tridecafluorooctyltriethoxysilane to anhydrous ethanol is 1:5-8.

[0015] In the preparation method of the biomimetic expanded graphite super-hydrophobic material, in step E, the centrifugal condition of the mixed dispersion B is 8000-10000 rpm, and the centrifugation is 8-15 min; the vacuum drying temperature is 65-75° C., and the vacuum drying time is 8-12 h.

[0016] The preparation method of the above-mentioned biomimetic expanded graphite super-hydrophobic material, in step A, the mass ratio of expanded graphite and nano zirconium dioxide is 1:2; the concentration of expanded graphite in the mixed dispersion A is 2.5wt%; the expanded graphite passes through a 200-mesh sieve, and the particle size of the nano zirconium dioxide is less than or equal to 100nm (in order to construct a rough surface morphology, nano-scale zirconium dioxide is selected to better combine with the micron-scale expanded graphite porous structure to form a dense and continuous super-hydrophobic coating);

[0017] In step B, the mass ratio of dopamine hydrochloride to tris(hydroxymethyl)aminomethane is 1:1, and the mass ratio of dopamine hydrochloride to expanded graphite is 8:125; the stirring reaction time is 6 hours;

[0018] In step C, the drying temperature is 60°C and the drying time is 12h;

[0019] In step D, anhydrous ethanol and P-ZrO 2 @The volume-to-mass ratio of EG material is 15 mL / g; the volume ratio of tridecafluorooctyl triethoxysilane to anhydrous ethanol is 1:6;

[0020] In step E, the centrifugal condition of the mixed dispersion B is 10000 rpm, centrifugation for 8 min; the vacuum drying temperature is 70° C., and the vacuum drying time is 10 h.

[0021] The super-hydrophobic composite coating is obtained by spraying the bionic expanded graphite super-hydrophobic material prepared by the above-mentioned preparation method of the bionic expanded graphite super-hydrophobic material onto a semi-cured epoxy resin primer and curing it.

[0022] The above-mentioned super-hydrophobic composite coating is prepared by the following steps:

[0023] Step (1), dispersing the epoxy resin and the curing agent into a mixed solvent, stirring and mixing to obtain an epoxy resin spray coating;

[0024] Step (2), spraying the epoxy resin spray coating onto the substrate, and placing it at room temperature for semi-curing to obtain an epoxy resin primer;

[0025] Step (3), dispersing the biomimetic expanded graphite super-hydrophobic material into anhydrous ethanol to obtain a super-hydrophobic material suspension;

[0026] Step (4), spraying the super-hydrophobic material suspension onto the surface of the epoxy resin primer and curing it at room temperature to obtain a super-hydrophobic composite coating.

[0027] In the super-hydrophobic composite coating, in step (1), the mass ratio of epoxy resin to curing agent is 2:1; the mass concentration of epoxy resin in the epoxy resin spray coating is 0.5 g / mL; the mixed solvent is formed by mixing n-butanol and xylene in a volume ratio of 3:7; the curing agent used in the present invention is a low molecular weight polyamide curing agent;

[0028] In step (2), the substrate is a Q235 steel plate, which is treated as follows before use: polished with 400-mesh and 1200-mesh sandpaper for 5 to 10 minutes, and cleaned with 70% alcohol by volume for 1 minute; when spraying, a K3 spray gun is used, the spray gun mouth is kept 10 cm away from the steel plate, and the spraying is performed for 1 minute; the semi-curing time is 2 hours;

[0029] In step (3), the mass fraction of the bionic expanded graphite super-hydrophobic material in the super-hydrophobic material suspension is 1 wt %;

[0030] In step (4), during spraying, a K3 spray gun is used, the spray gun mouth is kept 10 cm away from the steel plate, and spraying is performed for 1 min; after spraying, the amount of the super-hydrophobic material suspension on the substrate is 1 / 3 of the amount of the epoxy resin spray coating, and the curing time is 3 h.

[0031] The technical solution of the present invention achieves the following beneficial technical effects:

[0032] 1. The present invention uses expanded graphite and nano zirconium dioxide as bionic hydrophobic models and adopts a solution blending method to prepare a bionic expanded graphite super hydrophobic material PP-EG@ZrO 2 , PP-EG@ZrO 2 The super hydrophobic layer is combined with the epoxy resin coating to obtain a stable biomimetic expanded graphite epoxy resin-based super hydrophobic composite coating. The composite coating exhibits excellent chemical stability, mechanical durability and excellent self-cleaning / antifouling properties, and can provide a long-term anti-corrosion effect on the substrate.

[0033] 2. The biomimetic expanded graphite super-hydrophobic material prepared by the preparation method of the biomimetic expanded graphite super-hydrophobic material of the present invention has micro-nano secondary rough structure and hydrophobic functional group, after being sprayed on semi-cured epoxy resin primer, can be cured to form a super-hydrophobic composite coating, the rough surface structure makes air easy to be trapped in the groove to form a layer of air film, when the corrosive medium arrives at the coating surface, the corrosive medium can be effectively blocked, and the corrosive ions are difficult to reach the substrate surface, thereby the substrate is effectively protected.

[0034] 3, its porous micron-sized expanded graphite of super-hydrophobic coating of the present invention provides good framework for nano zirconium dioxide, and nano zirconium dioxide is distributed in coating surface to form stable and continuous micro-nano rough structure, and bottom epoxy resin is well bonded together, so that the structure of super-hydrophobic surface layer is more stable and not easily destroyed. Spraying epoxy resin coating between super-hydrophobic layer and substrate, on the one hand, can enhance the bonding force of super-hydrophobic layer and substrate, on the other hand, can form a composite coating having super-hydrophobic property and anti-corrosion property concurrently, so as to better block the erosion of corrosive medium to metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 In the embodiment of the present invention, tridecafluorooctyl triethoxysilane and dopamine hydrochloride are used to modify ZrO 2 Schematic diagram of the process with EG;

[0036] Figure 2 Schematic diagram of the preparation process of super hydrophobic coating in an embodiment of the present invention;

[0037] Figure 3a SEM image (100 μm) of pure EG in the embodiment of the present invention;

[0038] Figure 3b SEM image of PP-EG in the embodiment of the present invention (100 μm);

[0039] Figure 3c In the embodiment of the present invention, PP-EG@ZrO 2 SEM image (100 μm);

[0040] Figure 3d SEM image of pure EG in the embodiment of the present invention (2 μm);

[0041] Figure 3e SEM image of PP-EG in the embodiment of the present invention (2 μm);

[0042] Figure 3f In the embodiment of the present invention, PP-EG@ZrO 2 SEM image (2 μm);

[0043] Figure 4a1 to Figure 4a6 The EDS diagram of PP-EG in the embodiment of the present invention and the element distribution diagram of carbon, oxygen, silicon, fluorine and sodium;

[0044] Figure 4b1 to Figure 4b6 PP-EG@ZrO in the embodiment of the present invention 2 EDS images and element distribution maps of carbon, zirconium, fluorine, silicon and nitrogen;

[0045] Figure 5a The contact angle test results of EG in the embodiment of the present invention;

[0046] Figure 5b The contact angle test results of PP-EG in the embodiment of the present invention;

[0047] Figure 5c In the embodiment of the present invention, PP-EG@ZrO 2 Contact angle test results;

[0048] Figure 6a Physical image and CA image of EP coating in the embodiment of the present invention;

[0049] Figure 6b SEM image of EP coating in the embodiment of the present invention (50 μm);

[0050] Figure 6c SEM image of EP coating in the embodiment of the present invention (5 μm);

[0051] Figure 6d Physical image and CA image of SC-EP coating in the embodiment of the present invention;

[0052] Figure 6e SEM image of SC-EP coating in the embodiment of the present invention (50 μm);

[0053] Figure 6f SEM image of SC-EP coating in the embodiment of the present invention (5 μm);

[0054] Figure 7a SEM and CA images of the SC-EP coating in the embodiment of the present invention;

[0055] Figure 7b EDS spectrum of SC-EP coating in the embodiment of the present invention;

[0056] Figure 7c EDS spectrum carbon element distribution diagram of SC-EP coating in the embodiment of the present invention;

[0057] Figure 7d EDS spectrum oxygen element distribution diagram of SC-EP coating in an embodiment of the present invention;

[0058] Figure 7e EDS spectrum zirconium element distribution diagram of SC-EP coating in an embodiment of the present invention;

[0059] Figure 7f EDS spectrum fluorine element distribution diagram of SC-EP coating in the embodiment of the present invention;

[0060] Figure 7g EDS spectrum silicon element distribution diagram of SC-EP coating in an embodiment of the present invention;

[0061] Figure 7h EDS spectrum nitrogen element distribution diagram of SC-EP coating in the embodiment of the present invention;

[0062] Figure 8a XPS full spectrum of SC-EP coating in the embodiment of the present invention;

[0063] Figure 8b C1s peak spectrum of SC-EP coating in the embodiment of the present invention;

[0064] Figure 8c F1s peak spectrum of SC-EP coating in the embodiment of the present invention;

[0065] Figure 8d N1s peak spectrum of SC-EP coating in the embodiment of the present invention;

[0066] Figure 8e O1s peak spectrum of SC-EP coating in the embodiment of the present invention;

[0067] Figure 8fSi2s peak spectrum of SC-EP coating in the embodiment of the present invention;

[0068] Figure 9a Schematic diagram of sandpaper wear experiment in an embodiment of the present invention;

[0069] Figure 9b A graph showing the changing trend of the hydrophobic properties of the coating under different wear cycles in the embodiment of the present invention;

[0070] Fig.9c Schematic diagram of a tape peeling experiment in an embodiment of the present invention;

[0071] Figure 9d A graph showing the variation trend of the hydrophobic properties of the coating at different peeling times in an embodiment of the present invention;

[0072] Fig.10a SEM image of the sandpaper after 20 cycles of wear in the embodiment of the present invention (magnification 5000);

[0073] Fig.10b SEM image of the sandpaper after 20 cycles of wear in the embodiment of the present invention (magnification 10000);

[0074] Fig.11a SEM image of the tape after 30 strippings in the embodiment of the present invention (magnification 5000);

[0075] Fig.11b SEM image of the tape after 30 strippings in the embodiment of the present invention (magnification 10000);

[0076] Fig.12a Effect of immersion in pH=2 acid solution on the hydrophobicity of SC-EP coating in the embodiment of the present invention;

[0077] Figure 12b Effect of immersion in a pH = 12 alkaline solution on the hydrophobic properties of the SC-EP coating in the embodiment of the present invention;

[0078] Fig.12c Effect of immersion in 3.5wt% NaCl solution on the hydrophobicity of SC-EP coating in the embodiment of the present invention;

[0079] Fig.12d CA physical picture of the SC-EP coating in the embodiment of the present invention after being immersed in different corrosion solutions;

[0080] Figures 13a to 13c Schematic diagram of the self-cleaning performance of the EP coating in an embodiment of the present invention;

[0081] Figure 13d to Figure 13f Schematic diagram of the self-cleaning performance of the SC-EP coating in an embodiment of the present invention;

[0082] Figures 14a to 14c Schematic diagram of the antifouling performance of the SC-EP coating in an embodiment of the present invention;

[0083] Fig.15a Diagram of the initial state of water droplets on the surface of the EP coating in an embodiment of the present invention;

[0084] Fig.15b A diagram showing the state of water droplets starting to freeze on the surface of the EP coating in an embodiment of the present invention;

[0085] Fig.15c A diagram showing the freezing state of water droplets on the surface of the EP coating in an embodiment of the present invention;

[0086] Fig.15d Diagram of the initial state of water droplets on the surface of the SC-EP coating in an embodiment of the present invention;

[0087] Fig.15e A diagram showing the state of water droplets starting to freeze on the surface of the SC-EP coating in an embodiment of the present invention;

[0088] Fig.15f A diagram showing the freezing state of water droplets on the surface of the SC-EP coating in an embodiment of the present invention;

[0089] Fig.16a Polarization curves of the coating samples in the embodiment of the present invention after being immersed in 3.5wt% NaCl solution for 240h;

[0090] Fig.16b Polarization curves of the coating samples in the embodiment of the present invention after being immersed in 3.5wt% NaCl solution for 720h;

[0091] Figure 17a1 to Figure 17a3 Electrochemical impedance spectroscopy of the EP coating after immersion in 3.5wt% NaCl solution in the embodiment of the present invention;

[0092] Figure 17b1 to Figure 17b3 Electrochemical impedance spectroscopy of the SC-EP5 coating after immersion in 3.5wt% NaCl solution in the embodiment of the present invention;

[0093] Figure 17c1 to Figure 17c3 Electrochemical impedance spectroscopy of the SC-EP10 coating after immersion in 3.5wt% NaCl solution in the embodiment of the present invention;

[0094] Figure 17d1 to Figure 17d3 Electrochemical impedance spectroscopy of the SC-EP15 coating after immersion in 3.5wt% NaCl solution in the embodiment of the present invention;

[0095] Fig.18 Equivalent circuit diagram for fitting EIS data in an embodiment of the present invention;

[0096] Fig.19aSurface morphology of the EP coating after 720° salt spray corrosion treatment in the embodiment of the present invention;

[0097] Fig.19b Surface morphology of the SC-EP5 coating after 720° salt spray corrosion treatment in the embodiment of the present invention;

[0098] Fig.19c Surface morphology of SC-EP10 coating after 720° salt spray corrosion treatment in an embodiment of the present invention;

[0099] Fig.19d Surface morphology of the SC-EP15 coating after 720° salt spray corrosion treatment in an embodiment of the present invention. DETAILED DESCRIPTION

[0100] 1. Preparation of bionic expanded graphite super-hydrophobic material

[0101] Expanded graphite (EG) and zirconium dioxide (ZrO 2 ) comprises the following steps:

[0102] (1) Dopamine hydrochloride (DA) modified ZrO 2 @EG: Weigh the medicine with an electronic balance. Weigh 2.5g 200-mesh expanded graphite (EG) and 5g nano zirconium dioxide (ZrO 2 ), 2.5 g 200 mesh expanded graphite (EG) was then placed in two beakers, 100 mL ultrapure water (UP) solution was added, and 0.16 g dopamine hydrochloride (DA) and 0.16 g tris(hydroxymethyl)aminomethane) were added and mixed. After magnetic stirring for 6 h, the solutions in the two beakers were transferred to centrifuge tubes for centrifugal separation, washed with anhydrous ethanol for 3 times, and dried at 60 ° C for 12 h to obtain powder samples, which were named P-EG, P-ZrO 2 @EG. The particle size of nano zirconium dioxide is less than or equal to 100nm.

[0103] (2) PFOES hydrophobically modified P-EG, P-EG@ZrO 2 : Weigh 2g of P-EG and 2g of P-ZrO respectively 2 @EG was then placed in two beakers, 30 ml of anhydrous ethanol was added, and 5 mL of tridecafluorooctyl triethoxysilane (PFOES) was added and mixed. The solutions in the two beakers were added to centrifuge tubes for centrifugation. The centrifuge parameters were set, the speed was set to 10000 rpm, the centrifugation time was set to 8 min, and the centrifuge was washed twice by centrifugation with anhydrous ethanol and transferred to a culture dish. Then, it was placed in a vacuum drying oven at 70 ° C. When the solvent in the system was completely volatilized, the reaction products were collected to finally obtain hydrophobically modified EG and EG@ZrO 2The powder samples were named PP-EG and PP-EG@ZrO 2 DA and PFOES co-modified ZrO 2 The process diagram of EG is as follows Figure 1 shown.

[0104] 2. Preparation of super-hydrophobic coating

[0105] Figure 2 Schematic diagram of the preparation process of super hydrophobic coating. The super hydrophobic coating is prepared by a two-step spraying method. First, the surface of the steel plate (Q235) (150mm*100mm*1mm) is polished with 400 mesh and 1200 mesh sandpaper for 5-10min, and the surface of the steel plate is cleaned with alcohol for 1min. 5g of epoxy resin and 2.5g of low molecular weight polyamide curing agent are dispersed in a mixed solvent of 10mL of n-butanol and xylene (3:7), magnetically stirred for 10min, poured into a K3 spray gun (SHZ-DⅢ Gongyi Yuhua Instrument Co., Ltd.), the spray gun mouth is kept 10cm away from the steel plate, sprayed for 1min, and placed at room temperature for 2h to a semi-cured state to obtain an epoxy resin primer. Then PP-EG@ZrO with an addition amount of 0.5wt.%, 1wt.%, and 1.5wt.% (accounting for the mass fraction of the solution) is added. 2 Add it to 30mL of anhydrous ethanol, add it evenly into the spray gun, and spray three different amounts of PP-EG@ZrO on the surface of the semi-cured epoxy resin primer. 2 The suspension was prepared so that the amount of super-hydrophobic material suspension on the substrate was 1 / 3 of the amount of epoxy resin spray coating; after spraying, the bionic expanded graphite epoxy resin-based super-hydrophobic composite coating was cured at room temperature for 3 hours, and they were named SC-EP5, SC-EP10, and SC-EP15 respectively, and the pure EP coating was used as the control group and named EP.

[0106] 3. PP-EG@ZrO 2 Microstructure, chemical composition and wettability analysis

[0107] Figure 3a and Figure 3d The SEM images of EG at different magnifications are shown, and it can be clearly seen that it has a loose and porous worm-like structure with a size between 70-100μm. Figure 3b and Figure 3e These are the SEM images of PP-EG at different magnifications. Figure 3b It can be seen that the worm-like structure has fewer micropores on its surface and is attached with nanospheres. These small particles are formed by the oxidation and self-polymerization of dopamine hydrochloride on the surface of expanded graphite. The phenolic hydroxyl groups on its surface have a good adsorption effect, which makes the expanded graphite successfully wrapped. Figure 3c and Figure 3f PP-ZrO2 @EG SEM images at different magnifications show that there are two types of nanoparticles with different particle sizes wrapped on the surface of expanded graphite. The larger particles are nano ZrO 2 , and its surface was also successfully wrapped with PDA nanospheres, which were evenly distributed on the EG surface, forming a dense and rough structure on the EG surface.

[0108] The microscopic morphology and composition of the material were analyzed and characterized by energy dispersive spectroscopy. Figure 4a1 to Figure 4a6 As shown, it can be seen that PP-EG is composed of characteristic elements C, O, Si, F and N, and is evenly distributed on the surface of EG. The C element is inherent in EG itself, the N element comes from PDA, and O, Si and F come from PFOES, indicating that PDA and PFOES successfully modify EG. Figure 4b1 to Figure 4b6 Display PP-EG@ZrO 2 It is composed of characteristic elements C, Zr, Si, F and N. C and Zr come from EG and ZrO respectively. 2 In the figure, O, Si, and F come from PFOES. It can be seen that the three elements are evenly distributed on EG. Based on the above analysis, it is proved that poly PDA and PFOES successfully modify EG@ZrO 2 .

[0109] The contact angle of EG, PP-EG and PP-EG@ZrO 2 The contact angles of three samples were measured. Figure 5a to Figure 5c The contact angle test results of the three samples are as follows. Figure 5a It can be seen that the contact angle of EG is 87.6°, which is close to the hydrophobic state and shows hydrophilic properties; Figure 5b It can be seen that the contact angle of EG after PFOES modification is 126.1°, showing hydrophobic properties, indicating that the surface energy of expanded graphite is reduced after PFOES modification; Figure 5c , PP-EG@ZrO 2 The contact angle of the sample surface can reach 161.3°, showing an excellent super-hydrophobic state, indicating that nano ZrO 2 The addition of PFOES fills and wraps the expanded graphite well, and the hydrophobic chains introduced by PFOES also reduce their surface energy, making PP-EG@ZrO 2 Compared with pure EG, the wettability has been greatly improved, and the transformation from hydrophilicity to superhydrophobicity provides a good preparation for the next step of preparing superhydrophobic coating. Therefore, the superhydrophobic PP-EG@ZrO 2 The samples were used as fillers for superhydrophobic coatings, and the properties of the coatings were then further studied and analyzed.

[0110] 4. Analysis of the morphology and chemical composition of the SC-EP super-hydrophobic coating surface

[0111] The microstructure and wettability of the coating surface were analyzed and characterized by scanning electron microscopy and contact angle tester. Figure 6a , Figure 6b , Figure 6c The physical picture and SEM picture of pure EP coating. Figure 6d , Figure 6e , Figure 6f The actual picture and SEM picture of SC-EP coating. Figure 6a It can be seen that the contact angle of the pure EP coating is 50.8°, showing a hydrophilic state. Figure 6b , Figure 6c It can be found that its surface morphology is dense and smooth. Figure 6d The figure shows that the contact angle of the SC-EP coating is 158.6°, showing a superhydrophobic state. Figure 6e , Figure 6f It shows that there are many micro-nano rough protrusions on the surface of SC-EP coating. This micro-nano rough structure is composed of micron-sized EG and nano-ZrO modified by PFOES. 2 The super-hydrophobic coating is composed of a stack of layers. Due to its special morphological characteristics, the coating has good self-cleaning ability and can achieve effective wetting control on the substrate surface through simple operation. By tightly combining the micro-nanostructure with the epoxy resin on the surface of the metal substrate, the mechanical stability of the super-hydrophobic coating is significantly improved, and it is endowed with excellent and stable super-hydrophobicity.

[0112] The surface composition of SC-EP super-hydrophobic coating was analyzed and characterized by energy dispersive spectroscopy. Figure 7a The microscopic morphology of the SC-EP coating shows that it has an obvious micro-nano secondary rough structure, and its contact angle is 158.6°, showing a super-hydrophobic state. Figure 7b , Figure 7c to Figure 7h As shown, the SC-EP coating is composed of characteristic elements C, O, Zr, F, Si and N, whose weight percentages are 34.12%, 12.56%, 16.23%, 6.06%, 3.56% and 27.44% respectively. Figure 7c to Figure 7h From the element distribution diagram, it can be seen that C, O, Zr, F, Si and N elements can be evenly distributed and continuously and densely distributed on the coating surface, indicating that PFOES and PDA successfully modified EG@ZrO 2 The superhydrophobic property of SC-EP coating is determined by the micro-nano secondary roughness structure on its surface and the hydrophobic chains introduced in PFOES.

[0113] X-ray photoelectron spectroscopy (XPS) was used to further analyze the chemical composition and bonding state of the surface of the SC-EP superhydrophobic coating. Figure 8aThe full spectrum of the coating is shown. The strong peaks of F, O, N, C, Zr and Si are clearly visible. The high-resolution XPS spectra of C1s, F1s, N1s, O1s and Si2p are shown in Figure 2. Figure 8b , Figure 8c , Figure 8d , Figure 8e , Figure 8f As shown in Figure 2, the Cls spectrum can be decomposed into five peaks, namely -CC (283.60 eV), -CN (284.23 eV), -CO (285.42 eV), -C=O (286.80 eV) and -CF 2 (291.13eV). Figure 8c As shown in the figure, the F1s spectrum can be decomposed into -CF 2 (687.56eV), -CF 3 (688.89eV) two peaks. The appearance of these two peaks indicates that PFOES is successfully grafted onto the surface of EG through hydrolysis and condensation reaction. Figure 8d As can be seen, the N1s spectrum can be divided into three peaks: -N = (401.88 eV), -NH (401.10 eV), -NH 2 (398.82 eV), -NH 2 The appearance of indicated that PDA successfully modified EG. Figure 8e As shown in the figure, the O1s spectrum has three peaks, namely -Si-O (532.64 eV), -CO (531.06 eV) and ZrO 2 O 2- (529.16 eV), ZrO 2 The appearance of the peak indicates that nano ZrO 2 Successfully compounded with micron-sized EG. Figure 8f It can be seen that the two peaks appearing in the Si2p spectrum are -Si-O-Si (103.22 eV) and C-Si (102.04 eV). The above analysis shows that the EG@ZrO in the SC-EP superhydrophobic coating 2 The micro-nanoparticles were successfully co-modified with PFOES and PDA.

[0114] 5. Mechanical durability test

[0115] Figure 9a The following is a schematic diagram of the sandpaper wear experiment of SC-EP coating. 1200# sandpaper was used to cut a 50mm×50mm×1mm Q235 steel plate coated with SC-EP as the experimental object. A weight with a load of 100g was placed on the Q235 steel plate and pushed back and forth for a distance of 20cm. One back and forth push was defined as a wear cycle. After every 5 cycles, the contact angle and rolling angle were measured. Figure 9bThe figure shows the changing trend of water contact angle and rolling angle of the coating after different wear cycles. As the wear cycles increase, the water contact angle gradually decreases; however, after 20 wear cycles, i.e., a wear distance of 400 cm, the contact angle of the coating is still greater than 150°, and its rolling angle continues to increase with the increase of wear cycles. After the coating has undergone 20 wear cycles, it still has excellent superhydrophobic properties. The results show that the SC-EP superhydrophobic coating has excellent wear resistance. Fig.9c Schematic diagram of the tape stripping test of the SC-EP coating. The mechanical durability of the coating was tested by stripping the coating with tape multiple times. Fig.9c It can be seen that there are not many particles adhering to the surface of the tape, indicating that the coating has good adhesion. After continuous peeling tests, the water contact angle of the coating surface is gradually decreasing; Figure 9d The contact angle of the coating is still greater than 150° after 30 peeling cycles, showing excellent superhydrophobic properties, indicating that the SC-EP coating has stable mechanical durability.

[0116] Fig.10a and Fig.10b SEM images of the SC-EP coating at different magnifications after 20 cycles of sandpaper abrasion. Fig.10a It shows that after 20 times of friction and wear, the micron-scale EG on the surface of the super-hydrophobic coating was partially destroyed, while the nano-ZrO 2 Very evenly distributed on the coating surface, Fig.10b Under magnification, it can be seen that the coating still has a micro-nano secondary rough structure. On the one hand, although the surface micro-nano structure is partially destroyed, the porous micron-scale EG is nano-ZrO 2 Provides a good framework, nano ZrO 2 It is successfully distributed on the coating surface to form a stable and continuous micro-nano rough structure. On the other hand, the underlying epoxy resin bonds it well together, making the structure of the superhydrophobic surface more stable and less susceptible to damage.

[0117] like Fig.11a and Fig.11b As shown, SEM images of the SC-EP coating at different magnifications after 30 times of tape stripping. Fig.11a It can be seen that after 30 times of tape stripping experiments, the continuous and dense micro-nano rough structure on the surface of the super-hydrophobic coating was partially peeled off, but the nano-ZrO 2 There is still a dense and continuous distribution on the coating surface; Fig.11b Under magnification, we can see that nano ZrO 2 It is tightly combined with EG and firmly adheres to the epoxy resin base layer, making the micro-nano secondary rough structure not easily peeled off and damaged, and the super-hydrophobic surface has stable mechanical durability.

[0118] 6. Chemical stability test

[0119] Testing the stability of the coating in water is also particularly important for the protection of the metal substrate. Therefore, the coating was immersed in acid (pH = 2), alkaline (pH = 12) solution for 6 hours and 3.5wt.% NaCl (pH = 7) solution for 10 hours. As the immersion time continued to increase, the water contact angle (CA) and sliding angle (SA) of the coating were tested. Fig.12a and Figure 12b As shown in the figure, the CA of the SC-EP coating on the surface decreases and the SA increases with the immersion time in acid (pH = 2) and alkaline (pH = 12) aqueous solutions. After 5 hours of immersion, the CA is greater than 150° and the SA is less than 10°. Fig.12c It shows that after 10 hours of immersion in 3.5wt.% NaCl solution, the contact angle (CA) of the coating is greater than 150° and the rolling angle (SA) is less than 10°. This shows that the SC-EP coating has a stable barrier effect on neutral (PH=7) corrosive solution and can effectively prevent corrosive ions from reaching the metal surface and causing corrosion. The above analysis shows that the SC-EP super-hydrophobic coating has a good barrier effect on some strongly acidic and alkaline corrosive liquids (pH=2, 7 and 12). Fig.12d As shown in the figure, the SC-EP coating has good water repellency to solutions under different corrosion conditions. The prepared superhydrophobic coating exhibits excellent chemical stability.

[0120] 7. Self-cleaning and anti-fouling performance test

[0121] In the actual service process, the coating will inevitably be exposed to harsh outdoor environments, and the coating surface will be contaminated by some dust or tiny particles. The self-cleaning performance of the super-hydrophobic coating was tested experimentally. An appropriate amount of iron oxide powder was spread on the coating surface, and the sample was tilted to 30° with the horizontal plane. Then deionized water was dripped on the prepared coating surface to wash away the contaminants on the coating surface, as follows Fig.13a , Fig.13b , Fig.13c As shown, the surface of the pure EP coating is covered with the pollutant iron oxide powder. The coating surface is repeatedly washed with ultrapure water (UP). Because the coating surface is hydrophilic and has a small surface tension, the iron oxide powder has a strong adhesion to the coating surface, and the pollutants are sag, making it difficult to remove the pollutants on the surface. Fig.13d , Fig.13e , Fig.13fThe figure is a schematic diagram of the self-cleaning behavior of the SC-EP coating. When a water drop contacts the coating surface, it will slide down quickly due to the action of gravity, and the iron oxide pollutants on the coating will also slide down with the water drop. This is because the surface of the SC-EP coating is in a superhydrophobic state, forming a typical Cassie-Baxter model. When the water drop contacts the coating, the rough micro-nano structure and the hydrophobic functional groups grafted thereon will trap air in the surface gaps, forming air layers, which can well prevent the water drop from dripping and penetrating, so that the water droplets slide down quickly under the action of gravity, thereby cleaning the surface pollutants. The results show that the prepared SC-EP coating has excellent self-cleaning performance.

[0122] Figures 14a to 14c This is an experiment to test the antifouling performance of the SC-EP coating. Deionized water dyed with methylene blue, which is common in daily life, was selected as the contamination liquid, and then the SC-EP super-hydrophobic coating was immersed in the liquid. After repeated immersion and removal, the coating surface was very clean, and there was no sagging or infiltration of the contamination liquid. Fig.14c The reason for this is that there is a large amount of air in the dense and continuous micro-nano rough structure on the coating surface. When the SC-EP coating is immersed in the contaminated liquid, a continuous air layer will form on the surface. On the other hand, the introduction of fluorosilicone gives it a large surface tension, which will directly block the methylene blue contamination liquid from the coating surface. Through the above analysis, the SC-EP coating has excellent anti-fouling performance.

[0123] 8. Anti-icing performance test

[0124] The anti-icing performance of SC-EP coating was investigated. Figures 15a to 15f The whole process of water droplet freezing on the surface of EP coating and SC-EP coating is shown. Table 1 shows the specific values ​​of freezing time and freezing temperature of each coating. Fig.15a The figure shows the initial state of the water drop on the EP coating. Because the coating surface is hydrophilic, the water drop spreads over a large area on the pure EP coating surface. Fig.15d The water droplets on the surface of the SC-EP superhydrophobic coating appear to be stable spherical; Fig.15b This is the initial state of the water droplet freezing on the EP coating. It can be seen that the time when the water droplet starts to freeze is 240s; Fig.15c The water droplets on the EP coating are clearly frozen. It can be clearly seen that the water droplets on the surface of the EP coating are in the shape of a "flat ball", indicating that the ice has been completely frozen. The whole process lasted 296 seconds, the freezing process took 56 seconds, and the temperature when the ice was completed was -10.5℃. Fig.15d , Fig.15eIt can be seen that the water droplets on the surface of the SC-EP coating changed from transparent to "turbid" because the water droplets on the surface of the SC-EP coating began to freeze. The freezing time was 600s. After 285s, the water droplets on the surface of the SC-EP coating completely turned into a "spherical" shape. At this time, the water droplets were completely frozen, and the freezing temperature was -12.5℃. From the data in Table 3-1, it can be seen that compared with the water droplets on the surface of the pure EP coating, the freezing time of the water droplets on the surface of the SC-EP coating was extended by 229s, and the freezing temperature was also reduced by 2℃, indicating that the SC-EP coating has better anti-icing performance and can effectively delay the freezing time and reduce the freezing temperature. Fig.15e , Fig.15f The reason why the SC-EP coating has better anti-icing performance is shown. Since the surface of the SC-EP coating is super-hydrophobic, water droplets on the coating are in a very stable spherical shape, which makes the contact area between the water droplets and the coating surface small; while the surface of the pure EP coating is hydrophilic, when the water droplets contact the coating surface, a larger contact area will be formed. Since the contact area between the two coatings and the water droplets is quite different, the smaller the contact area, the slower the heat transfer, the slower the freezing time, and the lower the freezing temperature.

[0125] Table 1 Water drop freezing temperature and time on EP and SC-EP coating surfaces

[0126]

[0127] 9. Corrosion resistance test

[0128] To explore the PP-EG@ZrO 2 The effect of different addition amounts on the corrosion resistance of the superhydrophobic coating was studied. The corrosion resistance of each coating sample was evaluated using an electrochemical workstation. The superhydrophobic coating samples with addition amounts of 0.5wt.%, 1wt.% and 1.5wt.% were named SC-EP5, SC-EP10 and SC-EP15, respectively, and the pure epoxy resin (EP) coating was used as a blank control and named EP.

[0129] 9.1 Potentiodynamic Polarization Curve

[0130] Fig.16a and Fig.16b Table 2 is the comparison of polarization curves of EP coating and SC-EP coating after immersion in 3.5wt.%NaCl solution for 240h and 720h. Table 2 is the electrochemical data obtained from polarization curve fitting. After 240h immersion test, the corrosion current density (icorr) of SC-EP10 coating is 7.8x10 -11 A.cm -2Compared with the pure EP coating, its corrosion current density (icorr) is the smallest, with a difference of about 4 orders of magnitude. Even after immersion in 3.5wt.%NaCl solution for 720h, PP-EG@ZrO 2 The corrosion current density (icorr) of the SC-EP10 coating sample with an addition amount of 1 wt.% is also 5 orders of magnitude lower than that of the pure EP coating, which is 1.1x10 -10 A.cm -2 . In addition, the corrosion potential (Ecorr) of the super-hydrophobic coating samples with addition amounts of 0.5wt.%, 1wt.% and 1.5wt.% immersed in NaCl solution for 240h and 720h is greater than that of bare pure epoxy resin. However, the corrosion current density and corrosion potential have a great influence on the electrochemical corrosion rate. The greater the corrosion current density, the more energy is required for ion transmission, causing the metal surface to be dissolved quickly and the corrosion rate to increase accordingly. The polarization curve in the figure shows that the corrosion current generated by the SC-EP10 coating sample during the electrochemical corrosion process is the smallest and the corrosion potential is the largest, indicating that it has the best corrosion resistance. The reason for this is analyzed to be PP-EG@ZrO 2 With micro-nano secondary rough structure and hydrophobic functional groups, when the corrosive medium reaches the surface of the coating, the rough surface will effectively block the corrosive medium, making it difficult for the corrosive ions to reach the surface of the substrate, thereby effectively protecting the substrate. Among them, the SC-EP10 coating with an addition amount of 1wt.% has the best corrosion resistance, and the PP-EG@ZrO 2 It can be distributed more evenly on the coating surface to form a dense and continuous micro-nano rough structure, providing more long-term and effective protection for the coating.

[0131] Table 2 Comparison of polarization curve fitting parameters of coating samples after immersion in 3.5wt.%NaCl solution for 240h and 720h

[0132]

[0133] 9.2 Electrochemical Impedance Spectroscopy

[0134] Figure 17a1 to Figure 17d3 The electrochemical impedance spectra (EIS) of EP, SC-EP5, SC-EP10 and SC-EP15 coatings after immersion in 3.5wt.% NaCl solution for 0h, 24h, 240h, 480h and 720h are shown respectively. Figure 17a1 to Figure 17a3 The electrochemical impedance spectra of pure EP coating samples after immersion for different times. After immersion for 720 hours, the diameter of the capacitance loop is significantly reduced. It is well known that a larger low-frequency impedance modulus indicates better corrosion resistance. Fig.17a3 It can be seen that the corrosion resistance of the pure EP coating is reduced by about 5 orders of magnitude. As the immersion time increases, its corrosion resistance decreases sharply. Figure 17b1 to Figure 17d3 It is shown that after adding PP-EG@ZrO 2 The super-hydrophobic coatings after immersion have larger capacitance loop diameters and low-frequency impedance moduli. The SC-EP10 coating with an addition amount of 1wt.% has the best anti-corrosion performance. After immersion for 720h, the coating still has a large low-frequency impedance modulus (2.0×10 8 Ω·cm 2 Compared with the pure EP coating, it only increased by 4 orders of magnitude. The test results of electrochemical impedance spectroscopy and polarization curve are consistent. The results show that the SC-EP10 super-hydrophobic coating with an addition amount of 1wt.% has the best long-term corrosion resistance. The reason is that EG and ZrO in the SC-EP10 coating 2 It can be distributed more evenly to form a dense and continuous micro-nano rough structure, providing more long-term and effective protection for the coating.

[0135] In addition, in order to analyze the EIS measurement results in more detail, an equivalent circuit was used to fit the EIS spectrum. The equivalent circuit model is as follows: Fig.18 As shown, the fitting circuit consists of the coating resistance (R c ), coating capacitance (Q c ), charge transfer resistance (R ct ) and double layer capacitance (C dl ) c The higher the value, the better the barrier property of the coating, which also means that the coating has fewer defects. Table 3 shows that due to the lack of protection of the superhydrophobic surface layer, the R c The value is much lower than that of SC-EP coating. Studies have shown that the invasion of corrosive ions will lead to an increase in the dielectric constant of the coating, which is manifested as Q c The value of pure epoxy resin coating increases. c The value of Q of SC-EP10 coating is the largest during the immersion period, indicating that the aqueous solution can more easily penetrate this coating during the immersion process. c The value is the smallest, indicating that the coating has the best barrier performance. ct It reflects the electrochemical corrosion rate of the metal interface. Table 3 shows the R ct The highest value indicates the lowest metal corrosion rate, which is due to the fact that the air layer on the surface of the super-hydrophobic coating hinders the transfer of charges. dl Directly related to the metal area exposed to the electrolyte, C dl The higher the value, the greater the degree of coating damage. dlThe reason for the lower value is that the coating has good barrier properties and can inhibit the further occurrence of corrosion. The high resistance indicates that the coating can effectively protect the substrate from corrosion, and the low capacitance means a smaller corrosion area. In summary, the prepared SC-EP10 coating has excellent long-term corrosion resistance.

[0136] Table 3 EIS data fitting results of each coating sample after immersion in 3.5wt.%NaCl solution for 720h

[0137]

[0138] 9.3 Salt spray corrosion test

[0139] The salt spray accelerated corrosion test box was used to conduct a 720-h salt spray accelerated corrosion test on each coating sample, and the surface macroscopic morphology of each coating was compared. Fig.19a It is a pure EP coating, and reddish-brown Fe is generated at the cross scratches. 2 O 3 , the corrosion distribution range is the widest, and the damage caused by corrosion is the most serious. In addition, the surface of the pure EP coating has corrosion spots of different diameters, and the number is the largest, and the coating surface is most seriously corroded. Fig.19b , Fig.19c , Fig.19d It is shown that when PP-EG@ZrO 2 As the addition amount continued to increase, the number and area of ​​corrosion spots at the scratches of each coating sample continued to shrink. 2 When the addition amount is 1wt.%, the corrosion area and number of corrosion spots at the scratch of SC-EP10 coating are the smallest, the surface of the coating is the most intact, and its corrosion resistance is the best. Fig.19b and 19d As shown. When PP-EG@ZrO 2 When the addition amount of PP-EG@ZrO was 0.5wt.% and 1.5wt.%, the corrosion area at the cross scratch of the coating sample expanded to varying degrees, and the number of corrosion spots on it also increased. The results of the 720h salt spray accelerated corrosion test showed that when PP-EG@ZrO 2 When the addition amount is 1wt.%, the bionic expanded graphite super-hydrophobic anti-corrosion coating has the best corrosion resistance.

[0140] In summary, the present embodiment successfully prepared a biomimetic expanded graphite epoxy resin-based super-hydrophobic coating with long-term anticorrosion performance using a two-step spraying method, and its preparation method is simple and suitable for mass production. The surface morphology and chemical composition of the coating were analyzed, and the mechanical durability, chemical stability, self-cleaning and anti-corrosion properties of the super-hydrophobic coating were tested, and the following conclusions were obtained:

[0141] (1) PP-EG@ZrO modified with tridecafluorooctyltriethoxysilane (PFOES) was successfully prepared by solution blending method. 2 , the modified PP-EG@ZrO 2 The water contact angle reaches 158.6°, PP-EG@ZrO 2 The addition provided the basis for the micro-nano rough structure of the coating. Subsequently, the bionic expanded graphite epoxy resin-based superhydrophobic coating (SC-EP) was prepared by a two-step spraying method. The water contact angle and sliding angle of its surface were 158.6±1° and 4±1°, respectively, showing a superhydrophobic state.

[0142] (2) The surface morphology and composition of the SC-EP coating were analyzed using SEM, XPS, EDS and FT-IR, indicating that the micro-nano secondary rough structure and chemical composition together give the SC-EP coating excellent superhydrophobic properties.

[0143] (3) The results of sandpaper abrasion and tape stripping experiments show that the SC-EP coating still has good superhydrophobic properties after being worn for more than 400 cm on 1200# sandpaper; it still maintains good superhydrophobic properties after being immersed in strong acid and alkali solutions of pH=2 and pH=12 for 5 hours. The SC-EP coating has stable mechanical durability and good chemical stability.

[0144] (4) The results of self-cleaning and anti-fouling experiments show that the surface of the SC-EP super-hydrophobic layer can clean the dirt on the coating surface. The anti-icing experiment shows that the freezing time of the SC-EP coating is 229s longer than that of the EP coating, and the freezing temperature is reduced by 2°, indicating that the SC-EP coating has better anti-icing performance.

[0145] (5) The results of electrochemical tests and salt spray tests show that after 720 h of immersion in 3.5 wt.% NaCl solution, PP-EG@ZrO 2 The SC-EP10 coating with an addition amount of 1wt.% has the best anti-corrosion performance, the corrosion current density decreases by 2 orders of magnitude, and the lowest corrosion rate is 13.613mpy; it has a large low-frequency impedance modulus (|Z|), which is 2.0×10 8 Ω·cm 2 Compared with pure EP coating, it is improved by 4 orders of magnitude. The test results obtained by electrochemical impedance spectroscopy are consistent with the polarization curve. The salt spray test also shows that PP-EG@ZrO 2 The SC-EP10 coating with an addition amount of 1% has the smallest surface corrosion area and the least number of corrosion spots, the most intact coating surface, and the best corrosion resistance.

Claims

1. Super hydrophobic composite coating, It is characterized in that The biomimetic expanded graphite super-hydrophobic material is sprayed onto a semi-cured epoxy resin primer and cured; The preparation method of biomimetic expanded graphite super-hydrophobic material comprises the following steps: Step A, adding expanded graphite and nano zirconium dioxide to ultrapure water and stirring and mixing to obtain a mixed dispersion A; the mass ratio of expanded graphite to nano zirconium dioxide is 1:2; the concentration of expanded graphite in the mixed dispersion A is 2.5-3.0wt%; the expanded graphite is passed through a 200-mesh sieve, and the particle size of the nano zirconium dioxide is less than or equal to 100nm; Step B, adding dopamine hydrochloride and tris(hydroxymethyl)aminomethane to the mixed dispersion A, mixing and reacting by stirring; after the reaction is completed, centrifuging to obtain a solid product; the mass ratio of dopamine hydrochloride to tris(hydroxymethyl)aminomethane is 1:1, and the mass ratio of dopamine hydrochloride to expanded graphite is 1:15-16; the stirring reaction time is 5-8h; Step C: washing the solid product with anhydrous ethanol and drying it to obtain P-ZrO 2 @EG material; drying temperature is 55-65℃, drying time is 10-12h; Step D: P-ZrO 2 @EG material was re-dispersed in anhydrous ethanol, and tridecafluorooctyl triethoxysilane was added and stirred to obtain a mixed dispersion B; anhydrous ethanol and P-ZrO 2 @The volume-to-mass ratio of EG material is 15-20 mL / g; the volume ratio of tridecafluorooctyl triethoxysilane to anhydrous ethanol is 1:5-8; Step E, washing the solid after centrifugation of the mixed dispersion B with anhydrous ethanol, and then placing it in a vacuum drying oven for drying, and obtaining the bionic expanded graphite super-hydrophobic material after drying; the centrifugation conditions of the mixed dispersion B are 8000-10000 rpm, and the centrifugation is 8-15 minutes; the vacuum drying temperature is 65-75° C., and the vacuum drying time is 8-12 hours.

2. The super-hydrophobic composite coating according to claim 1, It is characterized in that In step A, the mass ratio of expanded graphite to nano zirconium dioxide is 1:2; the concentration of expanded graphite in the mixed dispersion A is 2.5wt%; the expanded graphite is passed through a 200-mesh sieve, and the particle size of the nano zirconium dioxide is less than or equal to 100nm; In step B, the mass ratio of dopamine hydrochloride to tris(hydroxymethyl)aminomethane is 1:1, and the mass ratio of dopamine hydrochloride to expanded graphite is 8:125; the stirring reaction time is 6 hours; In step C, the drying temperature is 60°C and the drying time is 12h; In step D, anhydrous ethanol and P-ZrO 2 @The volume-to-mass ratio of EG material is 15 mL / g; the volume ratio of tridecafluorooctyl triethoxysilane to anhydrous ethanol is 1:6; In step E, the centrifugal condition of the mixed dispersion B is 10000 rpm, centrifugation for 8 min; the vacuum drying temperature is 70° C., and the vacuum drying time is 10 h.

3. The super-hydrophobic composite coating according to claim 1, It is characterized in that Prepared by the following steps: Step (1), dispersing the epoxy resin and the curing agent into a mixed solvent, stirring and mixing to obtain an epoxy resin spray coating; Step (2), spraying the epoxy resin spray coating onto the substrate, and placing it at room temperature for semi-curing to obtain an epoxy resin primer; Step (3), dispersing the biomimetic expanded graphite super-hydrophobic material into anhydrous ethanol to obtain a super-hydrophobic material suspension; Step (4), spraying the super-hydrophobic material suspension onto the surface of the epoxy resin primer and curing it at room temperature to obtain a super-hydrophobic composite coating.

4. The super-hydrophobic composite coating according to claim 3, It is characterized in that In step (1), the mass ratio of epoxy resin to curing agent is 2:1; the mass concentration of epoxy resin in the epoxy resin spray coating is 0.5 g / mL; the mixed solvent is a mixture of n-butanol and xylene in a volume ratio of 3:7; In step (2), the substrate is a Q235 steel plate, which is treated as follows before use: polished with 400-mesh and 1200-mesh sandpaper for 5 to 10 minutes, and cleaned with 70% alcohol by volume for 1 minute; when spraying, a K3 spray gun is used, the spray gun mouth is kept 10 cm away from the steel plate, and the spraying is performed for 1 minute; the semi-curing time is 2 hours; In step (3), the mass fraction of the bionic expanded graphite super-hydrophobic material in the super-hydrophobic material suspension is 1 wt %; In step (4), during spraying, a K3 spray gun is used, the spray gun mouth is kept 10 cm away from the steel plate, and spraying is performed for 1 min; after spraying, the amount of the super-hydrophobic material suspension on the substrate is 1 / 3 of the amount of the epoxy resin spray coating, and the curing time is 3 h.

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