A layered graphene / epoxy resin composite coating and a preparation method thereof

Abstract

This invention provides a layered graphene / epoxy resin composite coating and its preparation method, including pretreatment of mussel adhesive protein (MAP) surface, and alternating preparation of EP film and graphene layers by spin coating and graphene self-assembly based on the Maragoni method to obtain a Lay-GEC coating. This invention utilizes the aforementioned layered graphene / epoxy resin composite coating and preparation method to achieve the self-assembly and horizontal orientation of graphene nanosheets on the water surface through the Maragoni effect, thereby improving the coating's density and barrier properties. Furthermore, the catechol groups of mussel protein enable spontaneous coordination repair at scratch sites, enhancing the coating's self-healing ability and durability.

Description

Technical Field

[0001] This invention relates to the field of composite coatings, and in particular to a layered graphene / epoxy resin composite coating and its preparation method. Background Technology

[0002] Traditional epoxy resin coatings are prone to scratches in corrosive marine environments, allowing corrosive media to penetrate and trigger substrate corrosion. While graphene possesses excellent barrier properties, its conductivity can promote electrochemical corrosion when the coating is damaged. Graphene also tends to aggregate in coatings, making it difficult to achieve uniform dispersion and directional alignment, thus affecting the coating's density and long-term corrosion resistance. Composite coatings using only mussel protein or graphene still have limitations in self-healing ability, adhesion, and durability.

[0003] The patent (CN202011527788.3) proposes a coating that directly combines mussel protein and graphene, using an immersion method to form the film. However, its coating structure is simple and does not involve multilayer alternating structures or graphene directional alignment technology. Although the patent emphasizes environmental protection and multifunctionality, it does not solve key issues such as the control of graphene alignment in the coating, interlayer bonding strength, and scratch self-healing. Summary of the Invention

[0004] The purpose of this invention is to provide a layered graphene / epoxy resin composite coating and its preparation method. The coating utilizes the Maragoni effect to achieve the self-assembly and horizontal orientation of graphene nanosheets on the water surface, thereby improving the coating's density and barrier properties. Furthermore, the catechol groups of mussel protein are used to achieve spontaneous coordination repair at scratches, enhancing the coating's self-healing ability and durability.

[0005] To achieve the above objectives, the present invention provides a method for preparing a layered graphene / epoxy resin composite coating, comprising the following steps: Mussel adhesive protein (MAP) surface pretreatment: Take mussel adhesive protein acid solution, adjust the pH value of mussel adhesive protein acid solution with buffer solution, then dilute, immerse dry and clean carbon steel in the diluted solution, then take out carbon steel, wash and air dry to obtain MAP / carbon steel. EP base film preparation: EP sol was spin-coated onto the MAP / carbon steel surface using a spin-coating method at a ratio of approximately 0.005 ml / mm. 2 After drying and standing, EP / MAP / carbon steel is obtained; Graphene self-assembly based on the Malagoni method: Graphene powder and anhydrous ethanol were ultrasonically mixed to obtain a 1 mg / mL graphene / ethanol mixed solution. The graphene / ethanol mixed solution was then added dropwise to deionized water to form a graphene / ethanol / water mixed solution, resulting in a graphene self-assembled film. EP / MAP / carbon steel was immersed in the graphene / ethanol / water mixed solution at an inclined angle. The film was then slowly lifted along a direction perpendicular to the inclined angle to transfer the graphene film onto the surface of EP / MAP / carbon steel. After drying, graphene / EP / MAP / carbon steel was obtained. Subsequently, EP sol was spin-coated onto the surface of graphene / EP / MAP / carbon steel to obtain EP / graphene / EP / MAP / carbon steel. A graphene layer was assembled on the surface of EP / graphene / EP / MAP / carbon steel using a graphene self-assembly method based on the Malagoni process. The spin-coating of EP sol and graphene assembly were repeated alternately multiple times to prepare the Lay-GEC coating.

[0006] Preferably, the mussel mucilage acid solution has a pH of 2-3, a concentration of 4-6 mg / mL, and a purity of 90-95%; the pH of the adjusted mussel mucilage acid solution is 2.3-8.7. The concentration of MAP in the diluted mussel mucin acid solution was 1 mg / mL.

[0007] Preferably, the graphene powder has a lateral dimension range of 5-10 μm and a thickness of 2 nm; The EP sol was prepared using a mass ratio of EP: curing agent: reactive diluent = 10:3.3:3.

[0008] Preferably, in the graphene / ethanol mixed solution, the ratio of graphene to ethanol is 1 mg: 1 mL; The volume ratio of deionized water to graphene / ethanol mixed solution is (10~50):1; EP / MAP / carbon steel is immersed in a graphene / ethanol / water mixed solution at an angle of 30-45 degrees.

[0009] Preferred spin coating process parameters: 3000 rpm for 30 seconds, 1500 rpm for 10 seconds, and 500 rpm for 20 seconds.

[0010] Preferably, the graphene film is transferred to the EP / MAP / carbon steel surface and then dried at a temperature of 40°C.

[0011] Preferably, the MAP / carbon steel coated with EP sol is dried at room temperature and left to stand for 24 hours.

[0012] Preferably, the surface roughness Sa of the carbon steel is 1.0±0.2μm.

[0013] Preferably, the carbon steel substrate is immersed in MAP solution for 1 hour, and then air-dried at room temperature for 24 hours.

[0014] A method for preparing a layered graphene / epoxy resin composite coating.

[0015] Therefore, the present invention employs the above-mentioned layered graphene / epoxy resin composite coating and preparation method, and the technical effects are as follows: The graphene nanosheets exhibit a dense, parallel arrangement with small horizontal and vertical spacing, and are layered and alternately distributed with the EP material. This structural design prevents the formation of conductive networks within the coating, effectively avoiding contact between the graphene and the metal interface, and maximizing the physical shielding effect of graphene. The low-frequency impedance modulus reaches 10. 10 Ω·cm 2 It improves resistance by an order of magnitude compared to pure epoxy coatings. After immersion in a 3.5wt% NaCl solution for 30 days, there was no significant decrease in impedance, and it remained high even after 220 days. After being scratched and immersed in a 3.5wt% NaCl solution for 84 hours, the erosion length at the scratch site decreased from 0.45 mm to 0 mm, achieving complete self-repair.

[0016] The coating exhibits an alternating EP-graphene multilayer structure (e.g., 4 layers of EP / 3 layers of graphene), with uniform thickness and no obvious defects. The graphene layers are horizontally oriented, and the EP penetrates into the interlayer gaps, enhancing interlayer bonding and density. Neutral salt spray tests show that the coating has a service life of >600 hours, and even after scratches, it can maintain >200 hours without rust, blistering, or peeling.

[0017] Mussel protein interface layer at the scratch site and Fe 3+ The formation of catechol-iron coordination compounds inhibits corrosion propagation. The MAP interface layer, approximately 120–150 nm thick, is rich in catechol groups and a hydrogen bond network, enhancing the adhesion between the coating and the substrate.

[0018] Employing a water-based self-assembly and spin-coating process, it eliminates the need for organic solvents, aligning with green manufacturing trends. Process parameters (such as the number of graphene layers, spin-coating speed, and pH value) are adjustable to meet diverse corrosion resistance and mechanical performance requirements. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process for the MAP / Lay-GEC coating. Figure 2 This is a microscopic morphological characterization diagram of the MAP interface layer; Figure 2 (a) Digital photograph; Figure 2 (b) shows the morphological characterization of SEM and the elemental distribution map of EDS surface scan, scale bar: 250 μm; Figure 2 (c) is the AFM topography diagram; Figure 2 (d) shows the contour curves at points I and II; Figure 3 Chemical characterization of the MAP interface layer: Figure 3 (a) is the full FTIR spectrum; Figure 3 (b) is the Raman spectrum; Figure 3 (c) is the XPS full spectrum; Figure 3 (d) is the high-resolution spectrum of element O; Figure 3 (e) is the high-resolution spectrum of element C; Figure 4 This is a cross-sectional characterization diagram of the Lay-GEC coating; Figure 4 (a) is a SEM image of the coating cross-section; Figure 4 (b) is a high-resolution image; Figure 4 (c) is a surface distribution diagram of carbon elements; Figure 5 Performance test graphs of the MAP / Lay-GEC coating system after immersion for 1 day, 10 days, 20 days and 30 days; Figure 5 (a) is Nyquist; Figure 5 (b) is the Bode-impedance diagram; Figure 5 (c) is the Bode-phase diagram; Figure 5 (d) Curve showing the change in coating resistance with immersion time; Figure 6 Digital photographs of different scratch-resistant coatings after neutral salt spray tests at 0, 24, 55, 100 and 200 h. Figure 6 (a) shows a pure EP coating; Figure 6 (b) is a Lay-GEC coating; Figure 6 (c) is a MAP / Lay-GEC coating; Figure 7 This is a graph showing the influence of the process parameters of the Maragoni process on the corrosion resistance of the composite coating. Figure 7 (a) is a Bode-impedance diagram; Figure 7 (b) is the Bode-phase diagram; Figure 7 (c) is the Tafel curve; Figure 7 (d) represents the corrosion rate and low-frequency impedance modulus |Z| for each sample. f=0.01Hz Statistical bar chart. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] 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.

[0022] Example 1 like Figure 1 As shown, a method for preparing a layered graphene / epoxy resin composite coating includes the following steps: Mussel adhesive protein surface pretreatment The carbon steel substrate surface was coarsely and finely polished using SiC sandpaper with grit sizes of 500#, 1000#, and 2000#, achieving a surface roughness Sa of 1.058 ± 0.186 μm. After polishing, surface oil and contaminant particles were ultrasonically removed in anhydrous ethanol solution, followed by cold air drying for later use. Mussel adhesive protein (MAP) was stored in a 1 wt% citric acid aqueous solution with a pH of 2.3, a concentration of 5 mg / mL, and a purity of 92%, containing MAP polymers / degradation products as impurities. It was stored at 4°C in a dark, low-temperature environment. Before preparation, an appropriate amount of MAP solution was taken out, and the pH was adjusted to 7.5 using a buffer solution prepared with citric acid and sodium hydroxide, and the concentration was diluted to 1 mg / mL. Subsequently, the dried and clean carbon steel substrate was immersed in the MAP solution for 1 hour to adsorb MAP molecules. After immersion, the carbon steel was vigorously shaken in deionized water to avoid residual loosely adsorbed MAP molecules on the surface. Finally, it was air-dried at room temperature for 24 hours to prepare MAP / carbon steel.

[0023] Based on the self-assembly method of graphene nanosheets using the Maragoni effect, a preparation process for a layered graphene / epoxy resin composite (Lay-GEC) coating is proposed. The main raw materials used in the experiment include: graphene powder (Nanjing Xianfeng Nanomaterials Co., Ltd., lateral dimensions ranging from 5-10 μm, thickness 2 nm), E-51 general-purpose epoxy resin (EP), T31 curing agent (Kunshan Beiya Chemical Co., Ltd.), reactive diluent (Zhicheng Plastics Co., Ltd.), anhydrous ethanol (analytical grade), spray-coated test-grade steel plate (Q235A, composition: Fe, 0.22wt% C, 0.35wt% Si, 1.40wt% Mn, 0.045wt% P, 0.05wt% S), deionized water, and a circular container (55 mm in diameter, 30 mm in depth). The specific preparation process is as follows: Step 1: Preparation of EP base film An EP substrate was prepared using spin coating, a common industrial method. Spin coating typically controls film thickness by adjusting the sol viscosity and spin coater speed. An EP sol was prepared with a mass ratio of EP:curing agent:reactive diluent = 10:3.3:3 and stirred thoroughly. The carbon steel sample was placed in the center of the spin coater, and the sol was added dropwise. A uniform EP layer was prepared using spin coating parameters of 3000 rpm for 30 s, 1500 rpm for 10 s, and 500 rpm for 20 s. The layer was then allowed to stand for 2 hours in a dry, room-temperature environment to obtain an EP / MAP / carbon steel substrate. The EP layer serves two purposes: first, it prevents direct contact between residual deionized water from the Maragoni process and the carbon steel substrate, avoiding corrosion-induced reduction in adhesion; second, its strong adhesion maintains the dense horizontal arrangement of graphene nanosheets on its surface, preventing shear damage to the graphene structure during spin coating.

[0024] Step 2: Graphene self-assembly based on the Maragoni method 50 mg of graphene powder was added to 50 mL of anhydrous ethanol solution and ultrasonically vibrated for 1 h to prepare a well-dispersed 1 mg / mL graphene / ethanol mixed solution. Then, an appropriate amount of the graphene / ethanol mixed solution was slowly added dropwise to deionized water (the volume ratio of deionized water to graphene / ethanol mixed solution was 10:1). A dense and uniform graphene self-assembled film was formed on the water surface, which has a higher surface tension. EP / MAP / carbon steel was immersed in the water at a 30-45 degree angle and slowly lifted along a direction perpendicular to the angle of inclination, transferring the graphene film to the EP / MAP / carbon steel surface. Residual graphene nanosheets could be recovered by vacuum filtration. Finally, residual water molecules from the transfer process were dried at 40°C to avoid cracks and pores caused by water evaporation. During this process, EP and graphene nanosheets bonded together with good adhesion, resulting in a graphene / EP / MAP / carbon steel mixture.

[0025] Step 3: Spin coating and penetration of the EP layer After the moisture in the parallel, densely packed graphene film is dried, a prepared EP sol is dropped onto the graphene surface. The EP film is then uniformly spin-coated onto the graphene surface using spin-coating parameters of 3000 rpm for 30 seconds, 1500 rpm for 10 seconds, and 500 rpm for 20 seconds. Due to the excellent bonding between the graphene nanosheets and EP, the highly oriented horizontal alignment of the graphene is not destroyed by the shear force generated during spin-coating. Furthermore, the EP sol penetrates into the gaps and defects between the graphene nanosheets, ensuring the density of the coating.

[0026] Step 4: Repeat steps 2 and 3 several times to prepare the Lay-GEC coating.

[0027] The microstructure of the Lay-GEC coating prepared in Example 1 was characterized as follows: To avoid the corrosion-promoting activity of graphene and the expansion of the scratched area caused by corrosion when the coating is scratched, and to enhance the reliability of the scratched Lay-GEC coating in marine environments, a pretreatment method of preparing a MAP interface layer on a carbon steel surface using an immersion method is proposed to achieve self-repair at the scratched area of ​​the composite coating. Using MAP film-forming ability and bonding strength as indicators, the MAP immersion process parameters were optimized, and the optimal pH of the MAP immersion solution was determined to be 7.5. Subsequently, the corrosion resistance of the MAP / Lay-GEC coating was evaluated through long-term immersion experiments and scratch-immersion experiments.

[0028] Electron microscopy revealed that MAP molecules are tiny spherical particles with nanometer-sized dimensions, and they are interconnected. The height profile of the edges indicates that the thickness of the adsorbed interfacial layer after immersion in MAP solution for 1 hour is approximately 120-150 nm. Figure 2 As shown.

[0029] The chemical properties of the MAP interface layer were characterized using FTIR and XPS. Figure 3 (a) shows the full FTIR spectrum of the MAP interface layer. 1518-1531 cm⁻¹ -1 The characteristic peak at ~1584 cm⁻¹ is the result of the combined effect of the NH stretching vibration peak in the main chain and the CC stretching vibration peak on the aromatic ring of the DOPA side chain, at ~1584 cm⁻¹. −1 and ~1392cm -1 The characteristic peaks at this location are mainly attributed to the stretching vibrations of C=O bonds in MAP and the bending vibrations of CN bonds in peptide bonds, demonstrating that MAP possesses a typical protein structure. In addition to the aforementioned peaks, the MAP interfacial layer exhibits peaks at ~1440 cm⁻¹. -1 This resulted in a relatively weak peak at ~1253 cm⁻¹. -1 The characteristic peak at 2800-3000 cm⁻¹ is due to the CO stretching and OH bending vibrations of the DOPA phenolic hydroxyl groups, which is closely related to the adhesion and corrosion inhibition effects of the MAP interface layer. -1 The characteristic peaks in the vicinity indicate that the MAP contains a large number of hydrogen bonds.

[0030] Figure 3 (b) shows the Raman spectrum of MAP adsorbed on the carbon steel surface. As can be seen from the figure, the MAP interface layer at 1269 cm⁻¹... -1 1325cm -1 (νC−O + νC−Carom) and 1482cm -1 Three distinct characteristic peaks were generated at (νC−Carom), corresponding to the phenolic hydroxyl groups of catechol on the DOPA ring. These peaks are due to the formation of Fe during adsorption on the carbon steel matrix. 3+ Ions, MAP interface layer at 460-700 cm -1Three distinct characteristic peaks were formed at 586 cm⁻¹. -1 The characteristic peak at 631 cm⁻¹ is produced by the chelate formed by catechol and ferric ions, while the peak at 631 cm⁻¹ is produced by the chelate formed by catechol and ferric ions. -1 This is due to νFe-O. Figure 3 (c) to Figure 3 (e) shows the XPS spectrum of the MAP interface layer. The MAP interface layer mainly contains five elements: Na, C, O, N, and Si. Among them, C accounts for 62.94%, O for 29.41%, N for 7.1%, Si for 0.14%, and the remainder is Na. The Na and Si elements mainly come from the pH-adjusting buffer solution and residues from sandpaper polishing, while the C, O, and N elements originate from the protein structure of MAP. The high-resolution XPS spectra of O 1s and C 1s show the typical binding energies of hydroxyl groups (531.38~532.38 eV), CC (285.04 eV), CN (285.50 eV), and C-OH bonds (287 eV), confirming the presence of carbon chains, catechol groups, and peptide bonds in MAP.

[0031] The Lay-GEC coating consists of three graphene layers and four EP layers, exhibiting an alternating layered distribution with clear delamination between the structural layers. The coating cross-section is uniform and free of obvious defects. The thickness of the 4E / 3G coating is approximately 97.1 μm, the first EP base film is approximately 36 μm thick, and the second, third, and fourth EP layers are approximately 18 μm thick. Figure 4 (b) to Figure 4 (c) It can be seen that exposed transparent graphene nanosheets can be observed at the boundaries of each layer. At the same time, the EDS carbon element surface distribution map is brighter at the boundaries, indicating that the carbon element content is higher at the boundaries, which further proves the region where the graphene is located.

[0032] Corrosion resistance characterization: The EIS spectra of the MAP / Lay-GEC coating were examined using long-term immersion experiments after immersion for 1, 10, 20, and 30 days. The results are as follows: Figure 5 As shown in the Nyquist plot, the radius of curvature of the coated capacitor arc remains consistently at 10¹⁰ Ω·cm. 2 The order of magnitude, and the Bode-impedance plot shows that the low-frequency impedance modulus |Z| of the composite coating is on the order of magnitude. f=0.01Hz Up to 10¹⁰Ω / cm 2Compared to the pure EP coating, the resistance was improved by approximately an order of magnitude, and no significant degradation occurred after immersion in 3.5wt% NaCl solution for 30 days. The time constant in the Bode-phase angle plot consistently showed only one peak, concentrated in the high-frequency range, indicating that the electrochemical reaction occurred only on the coating surface, and the corrosive medium had not yet penetrated into the coating / metal interface. These EIS results demonstrate that the MAP / Lay-GEC coating possesses excellent corrosion resistance and durability, and that the MAP-based pretreatment process does not significantly affect the density and physical shielding performance of the Lay-GEC coating. Subsequently, the MAP / Lay-GEC coating was further immersed, and its EIS curve changes were recorded. An equivalent circuit was used to fit the coating resistance change trend, and the results are as follows: Figure 5 As shown in (d), the coating resistance of the MAP / Lay-GEC coating remained at 10¹⁰ Ω·cm after immersion for 220 days. 2 This indicates that its corrosion protection life is over 220 days.

[0033] The MAP interface layer can prevent the formation of loose and porous corrosion products at the scratch site, and spontaneously forms a dense and smooth catechol-iron coordination compound film at the interface, achieving self-repair of the coating at the scratch site. This effectively prevents the coating from propagating corrosion at the scratch site. After immersion in 3.5wt% NaCl solution for 84 hours, the unidirectional corrosion propagation length at the scratch site decreased from 0.45 mm to 0 mm. Finally, the salt spray resistance and interfacial bonding strength of the coating were examined using neutral salt spray tests and micro-scratch tests. The study showed that the service life of the MAP / Lay-GEC coating was over 600 hours in the neutral salt spray test, and the corrosion protection life of the coating after scratching was over 200 hours. No rusting, blistering, cracking, or peeling was observed after the salt spray test. Figure 6 As shown.

[0034] Example 2: Comparison of layered graphene / epoxy resin composite coatings with different numbers of graphene layers Step 1: Preparation of EP base film The surface of a carbon steel substrate (20mm × 20mm × 1mm) was polished using SiC sandpaper with grit sizes of 500#, 1000#, and 2000#. After polishing, surface oil and contaminant particles were ultrasonically removed in anhydrous ethanol solution. The surface roughness Sa of the polished carbon steel was 1.058 ± 0.186 μm. After cold air drying, it was ready for use. An EP base film was prepared using the spin coating method commonly used in the industrial field. The spin coating method generally controls the film thickness by adjusting the sol viscosity and the spin coater speed. An EP sol was prepared with a mass ratio of EP:curing agent:reactive diluent = 10:3.3:3 and stirred evenly. The carbon steel sample was placed in the center of the spin coater and the sol was added dropwise. A uniform EP layer was prepared by spin coating parameters of 3000 rpm for 30 s, 1500 rpm for 10 s, and 500 rpm for 20 s. The layer was then allowed to stand in a dry room temperature environment for 2 hours. The EP layer serves two purposes: first, it prevents the deionized water remaining in the Maragoni process from directly contacting the carbon steel substrate, thus avoiding problems such as reduced adhesion caused by corrosion; second, it utilizes its strong adhesion to maintain the dense horizontal arrangement of graphene nanosheets on its surface, avoiding the destructive effect of shearing on the graphene structure during spin coating.

[0035] Step 2: Graphene self-assembly based on the Maragoni method 50 mg of graphene powder was added to 50 mL of anhydrous ethanol solution and ultrasonically vibrated for 1 h to prepare a well-dispersed 1 mg / mL graphene / ethanol mixed solution. Then, an appropriate amount of the graphene / ethanol mixed solution was slowly added dropwise to deionized water, forming a dense and uniform graphene self-assembled film on the water surface with higher surface tension. An EP / carbon steel sample was immersed in the water at a 30-45 degree angle and slowly lifted along a direction perpendicular to the angle of inclination, transferring the graphene film to the sample surface. Residual graphene nanosheets could be recovered by vacuum filtration. Finally, residual water molecules from the transfer process were dried at 40°C to avoid cracks and pores caused by water evaporation. During this process, EP and graphene nanosheets bonded together, exhibiting good adhesion.

[0036] Step 3: Spin coating and penetration of the EP layer After the moisture in the parallel, densely packed graphene film is dried, a prepared EP sol is dropped onto the graphene surface. The EP film is then uniformly spin-coated onto the graphene surface using spin-coating parameters of 3000 rpm for 30 seconds, 1500 rpm for 10 seconds, and 500 rpm for 20 seconds. Due to the excellent bonding between the graphene nanosheets and EP, the highly oriented horizontal alignment of the graphene is not destroyed by the shear force generated during spin-coating. Furthermore, the EP sol penetrates into the gaps and defects between the graphene nanosheets, ensuring the density of the coating.

[0037] Step 4: Repeat steps 2 and 3 several times to prepare the Lay-GEC coating. The performance test results of the prepared coating are as follows: Figure 7 As shown.

[0038] Therefore, this invention employs the aforementioned layered graphene / epoxy resin composite coating and preparation method, utilizing the Maragoni effect to achieve the self-assembly and horizontal orientation of graphene nanosheets on the water surface, thereby enhancing the coating's density and barrier properties. Furthermore, the catechol groups of mussel protein are used to achieve spontaneous coordination repair at scratches, improving the coating's self-healing ability and durability.

[0039] 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 layered graphene / epoxy resin composite coating, characterized by, Includes the following steps: Mussel adhesive protein (MAP) surface pretreatment: Take mussel adhesive protein acid solution, adjust the pH value of mussel adhesive protein acid solution with buffer solution, then dilute, immerse dry and clean carbon steel in the diluted solution, then take out carbon steel, wash and air dry to obtain MAP / carbon steel. EP substrate preparation: EP sol was spin-coated onto the surface of MAP / carbon steel using a spin coating method, and then dried and allowed to stand to obtain EP / MAP / carbon steel; Graphene self-assembly based on the Malagoni method: Graphene powder and anhydrous ethanol are ultrasonically mixed to obtain a graphene / ethanol mixed solution. The graphene / ethanol mixed solution is then added dropwise to deionized water to form a graphene / ethanol / water mixed solution, resulting in a graphene self-assembled film. EP / MAP / carbon steel is immersed in the graphene / ethanol / water mixed solution at an inclined angle. The film is then slowly lifted along a direction perpendicular to the inclined angle to transfer the graphene film onto the surface of the EP / MAP / carbon steel. After drying, graphene / EP / MAP / carbon steel is obtained. Subsequently, EP sol was spin-coated onto the surface of graphene / EP / MAP / carbon steel to obtain EP / graphene / EP / MAP / carbon steel. A graphene layer was assembled on the surface of EP / graphene / EP / MAP / carbon steel using a graphene self-assembly method based on the Malagoni process. The spin-coating of EP sol and graphene assembly were repeated alternately multiple times to prepare the Lay-GEC coating.

2. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, The mussel mucin acid solution has a pH of 2-3, a concentration of 4-6 mg / mL, and a purity of 90-95%; after adjustment, the pH of the mussel mucin acid solution is 2.3-8.

7. The concentration of MAP in the diluted mussel mucin acid solution was 1 mg / mL.

3. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, The graphene powder has a lateral dimension ranging from 5 to 10 μm and a thickness of 2 nm. The EP sol was prepared using an EP: curing agent: reactive diluent mass ratio of 10:3.3:

3. The ratio of EP sol spin coating was 0.005 ml / mm 2 .

4. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, In the graphene / ethanol mixed solution, the ratio of graphene to ethanol is 1 mg: 1 mL; The volume ratio of deionized water to graphene / ethanol mixed solution is (10~50):1; EP / MAP / carbon steel is immersed in a graphene / ethanol / water mixed solution at an angle of 30-45 degrees.

5. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, Spin coating process parameters: 3000 rpm for 30 seconds, 1500 rpm for 10 seconds, and 500 rpm for 20 seconds.

6. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, The graphene film was transferred to the surface of EP / MAP / carbon steel and then dried at a temperature of 20-50℃.

7. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, MAP / carbon steel coated with EP sol was dried at room temperature and allowed to stand for 0.5-2 days.

8. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, The surface roughness Sa of carbon steel is 1.0±0.2μm.

9. The method for preparing a layered graphene / epoxy resin composite coating according to claim 1, characterized in that, The carbon steel substrate is immersed in MAP solution for 0.5-1.5 hours, and then air-dried at room temperature.

10. The layered graphene / epoxy resin composite coating prepared by the method for preparing a layered graphene / epoxy resin composite coating according to any one of claims 1-9.

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