A graphene-based anticorrosive coating and a preparation method thereof

Abstract

The application discloses a kind of anticorrosive coating based on graphene and preparation method, it is related to anticorrosive coating field, the preparation method includes the following steps: polyurethane prepolymer with flexible polyether main chain is grafted copolymerization with initial epoxy resin, and modified epoxy resin is obtained;Primary grafting modification is carried out to dispersion liquid containing graphene oxide a, and graphene oxide b is obtained;Again, graphene oxide b is carried out again grafting modification, and post-processing is carried out, and modified graphene is obtained;Preparation includes modified graphene slurry, and slurry is mixed with functional filler, and composite slurry is obtained;Modified epoxy resin is mixed with composite slurry, and main agent is obtained;Before coating, main agent is mixed with curing agent to form coating, and coating is coated on substrate and is cured, and anticorrosive coating is obtained.The application is synergized by chemical modification and physical blending, so that the obtained anticorrosive coating has excellent physical barrier performance, mechanical property and long-term protection effect.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coatings, and more particularly to an anti-corrosion coating based on graphene and its preparation method. Background Technology

[0002] Graphene, due to its excellent mechanical properties, barrier properties, and chemical stability, is widely considered a promising anti-corrosion filler and has received continuous attention in the field of anti-corrosion coatings. Theoretically, graphene's ultra-high aspect ratio and dense sheet structure can form tortuous diffusion paths in coatings, effectively delaying the penetration of moisture, oxygen, and corrosive ions, thus improving the coating's corrosion resistance. However, in practical applications, graphene suffers from poor dispersion stability and weak interfacial bonding in anti-corrosion coating systems, hindering its effective anti-corrosion performance. Specifically, due to graphene's large specific surface area and high surface energy, van der Waals forces easily occur between the sheets, leading to severe agglomeration and uneven dispersion in the resin matrix, making it difficult to form a continuous and effective barrier structure. Furthermore, unmodified graphene has poor interfacial compatibility with commonly used epoxy or polyurethane film-forming resins, resulting in insufficient interfacial bonding and the formation of micropores and defects at the interface. These micropores become preferential channels for corrosive media penetration, weakening the overall protective effect of the coating and potentially causing electrochemical corrosion due to the formation of localized conductive pathways.

[0003] Therefore, a graphene-based anti-corrosion coating and its preparation method are proposed to solve the problem that graphene has poor dispersion stability and weak interfacial bonding in the anti-corrosion coating system, which makes it difficult to effectively exert its anti-corrosion performance. Summary of the Invention

[0004] The purpose of this invention is to provide a graphene-based anti-corrosion coating and its preparation method, which solves the problem that the poor dispersion stability and weak interfacial bonding of graphene in the anti-corrosion coating system make it difficult to effectively exert the anti-corrosion performance.

[0005] To achieve this objective, the present invention adopts the following technical solution: A method for preparing a graphene-based anti-corrosion coating, the method comprising the following steps: Step S1: Graft copolymerize the polyurethane prepolymer with a flexible polyether backbone with the initial epoxy resin to obtain the modified epoxy resin. Step S2: The dispersion containing graphene oxide a is subjected to initial graft modification to obtain graphene oxide b; then the graphene oxide b is subjected to further graft modification and post-processing to obtain modified graphene. Step S3: Prepare a slurry containing modified graphene, and mix the slurry with functional fillers to obtain a composite slurry; Step S4: Mix the modified epoxy resin with the composite slurry to obtain the main agent; before coating, mix the main agent with the curing agent to form a coating, then apply the coating to the substrate for curing to obtain an anti-corrosion coating.

[0006] Step S1 specifically includes the following steps: Step S11: Add polyether diol a to a reaction vessel and dehydrate it at a temperature of 110-120℃, a vacuum degree of (-0.08)-(-0.1) MPa, and a time of 1.5-2h to obtain polyether diol b; Step S12: Cool system a in the reactor to 50-60℃, add isophorone diisocyanate to the reactor, then heat system a to 80-85℃ and react under nitrogen for 2-3 hours to obtain polyurethane prepolymer. Step S13: The initial bisphenol A type epoxy resin is heated to 80-90℃ in the reaction vessel, and the polyurethane prepolymer is added dropwise to the reaction vessel over 1-1.5 hours while stirring. After the dropwise addition is completed, the system b in the reaction vessel is heated to 90-100℃ and reacted for 2-3 hours to obtain the modified epoxy resin.

[0007] In step S11, the water content of the polyether diol b is ≤0.05%; In step S12, the molar ratio of isocyanate groups to hydroxyl groups in the isophorone diisocyanate is (2.0-2.2):1; during the reaction, the isocyanate group content of system a is measured every 30 minutes, and the reaction progress is tracked by the di-n-butylamine method until the isocyanate group content reaches 8.5-9.5% of system a, and then the reaction is stopped. In step S13, the mass ratio of the polyurethane prepolymer to the initial epoxy resin is (30-40):(60-70).

[0008] Step S2 specifically includes the following steps: Step S21: Add graphene oxide a to the mixed solvent and use ultrasound to intermittently sonicate the mixed solvent with a power of 500-800W for 30-60min. Then add glacial acetic acid to the mixed solvent to obtain a dispersion. Step S22: Hexadecyltrimethoxysilane and ethanol are stirred to obtain mixture a. Under stirring, mixture a is added dropwise to a dispersion at 60-65℃ within 30-45 min, and the mixture is stirred and reacted for 4-5 h to obtain system c containing graphene oxide b. Step S23: KH560 and ethanol are stirred to obtain mixture b. Mixture b is added dropwise to system c at 60-65℃ under stirring for 20-30 min and stirred for 2-3 h to obtain system d containing graphene oxide c. Step S24: Centrifuge system d at 8000-10000 rpm for 15-20 min to obtain a separated solid. Then, wash the separated solid with anhydrous ethanol by centrifugation multiple times to obtain graphene oxide c. Dry graphene oxide c at 60-70℃ and -0.09 MPa vacuum for 12-24 h, and then grind and sieve it to obtain modified graphene.

[0009] In step S21, the graphene oxide a has a sheet diameter of 5-10 μm, a thickness of 1-3 nm, and an oxygen content of 35-40%. The mixed solvent includes ethanol and water in a volume ratio of 80:20. The dispersion has a pH of 4.0-5.0 and a solid content of 0.5-1.0 wt%. In step S22, the mass of the hexadecyltrimethoxysilane is 20-30% of the mass of graphene oxide a; the volume ratio of the hexadecyltrimethoxysilane to ethanol is 1:(2-3). In step S23, the mass of KH560 is 10-20% of the mass of graphene oxide a, and the volume ratio of KH560 to ethanol is 1:(2-3). In step S24, the mesh size of the sieve is 200-250.

[0010] Step S3 specifically includes the following steps: Step S31: Add the modified graphene to the butyl acetate solvent and disperse at 1500-2000 rpm for 30-45 min to obtain a slurry; Step S32: Add the organically modified montmorillonite to the slurry and disperse it at a speed of 2000-2500 rpm for 20-30 minutes, then perform ultrasonic degassing treatment for 10-15 minutes to obtain the composite slurry.

[0011] In step S31, the solid content of the slurry is 5-8 wt%. In step S32, the sheet diameter of the organic modified montmorillonite is 200-500 nm, and the mass ratio of the organic modified montmorillonite to the modified graphene is (25-30):(70-75).

[0012] Step S4 specifically includes the following steps: Step S41: Stir the modified epoxy resin, composite slurry, leveling agent and defoamer at 800-1000 rpm for 20-30 min to obtain a mixture, and then mix the mixture with butyl acetate to obtain the main agent; Step S42: Before coating, mix the main agent and the curing agent and stir at 600-800 rpm for 3-5 minutes to obtain the coating; use air spraying method to spray the coating onto the substrate surface with a spraying pressure of 0.4-0.6 MPa through a nozzle with a diameter of 1.5-2.0 mm to form a wet film. Step S43: After curing the substrate with the film layer at 60°C for 24 hours, it is naturally cooled to room temperature to obtain the anti-corrosion coating.

[0013] In step S41, the modified epoxy resin, composite slurry, leveling agent and defoamer are 70-85 parts by weight, 10-25 parts by weight, 0.5-1.0 parts by weight and 0.2-0.5 parts by weight, respectively, and are adjusted with butyl acetate to a total weight of 100 parts by weight. In step S42, the mass ratio of the main agent to the curing agent is 100:(15-25), and the curing agent is a polyurethane curing agent, and the thickness of the wet film is 120-220μm; In step S43, the thickness of the anti-corrosion coating is 80-120 μm.

[0014] A graphene-based anti-corrosion coating, wherein the graphene-based anti-corrosion coating is prepared by the preparation method described above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a graphene-based anti-corrosion coating and its preparation method. The method first involves graft copolymerizing a polyurethane prepolymer with a flexible polyether backbone with an initial epoxy resin to prepare a modified epoxy resin that combines the high adhesion of epoxy resin with the flexibility of polyurethane, providing a good mechanical basis for the main film-forming material. Then, a dual graft modification process is performed on graphene oxide using both primary and secondary graft modifications, resulting in the simultaneous formation of a steric hindrance layer, a hydrophobic barrier, and reactive epoxy groups on the surface of the modified graphene. This effectively solves the problem of graphene's corrosion resistance in the steric hindrance layer. The agglomeration problem in epoxy resin provides chemical anchoring sites for its participation in subsequent crosslinking. Subsequently, modified graphene is blended with functional fillers to prepare a composite slurry. The synergistic effect of the functional fillers and modified graphene constructs a preliminary multi-scale physical barrier network, laying the structural foundation for the further formation of the maze effect. Finally, the composite slurry is mixed and cured with modified epoxy resin and a curing agent, allowing the modified graphene to be chemically anchored in the crosslinked network and form a dense barrier structure together with the functional fillers, significantly extending the penetration path of corrosive media. Therefore, this invention, through the synergistic effect of chemical modification and physical blending, fully utilizes the maze effect constructed by modified graphene and functional fillers, based on the stress buffer provided by the flexible polyether backbone, significantly improving the dispersion stability and interfacial bonding strength of graphene. This results in an anti-corrosion coating that possesses excellent physical barrier properties, mechanical properties, and long-term protective effects. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0018] Figure 1 This is a flowchart of the preparation method in this invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component positioned centrally in the connection.

[0021] Please see Figure 1 This embodiment describes a method for preparing a graphene-based anti-corrosion coating, which includes the following steps: Step S1: Graft copolymerize the polyurethane prepolymer with a flexible polyether backbone with the initial epoxy resin to obtain the modified epoxy resin. Step S2: The dispersion containing graphene oxide a is subjected to initial graft modification to obtain graphene oxide b; then the graphene oxide b is subjected to further graft modification and post-processing to obtain modified graphene. Step S3: Prepare a slurry containing modified graphene, and mix the slurry with functional fillers to obtain a composite slurry; Step S4: Mix the modified epoxy resin with the composite slurry to obtain the main agent; before coating, mix the main agent with the curing agent to form a coating, then apply the coating to the substrate for curing to obtain an anti-corrosion coating.

[0022] Specifically, in step S1, a polyurethane prepolymer with a flexible polyether backbone is grafted copolymerized with an initial epoxy resin to obtain a modified epoxy resin. Step S1 specifically includes the following steps: Step S11: Polyether diol a (brand name N220, molecular weight 2000) is added to a reaction vessel and dehydrated at a temperature of 110-120℃, a vacuum degree of (-0.08)-(-0.1) MPa, and a time of 1.5-2h to obtain polyether diol b; In step S11, the water content of polyether diol b is ≤0.05%; Step S12: Cool system a in the reactor to 50-60℃, add isophorone diisocyanate to the reactor, then heat system a to 80-85℃ and react under nitrogen for 2-3 hours to obtain polyurethane prepolymer. In step S12, the molar ratio of isocyanate groups to hydroxyl groups in isophorone diisocyanate is (2.0-2.2):1; during the reaction, the isocyanate group content of system a is measured every 30 minutes, and the reaction progress is tracked by the di-n-butylamine method until the isocyanate group content reaches 8.5-9.5% of system a, and then the reaction is stopped. Step S13: The initial epoxy resin of type bisphenol A (brand name E-44, epoxy equivalent of 210-230 g / eq) is heated to 80-90℃ in a reaction vessel, and the polyurethane prepolymer is added dropwise to the reaction vessel over 1-1.5 hours while stirring. After the dropwise addition is completed, the system b in the reaction vessel is heated to 90-100℃ and reacted for 2-3 hours to obtain the modified epoxy resin.

[0023] In step S13, the mass ratio of polyurethane prepolymer to initial epoxy resin is (30-40):(60-70).

[0024] It should be noted that step S1 aims to prepare a modified epoxy resin via a chemical grafting reaction, serving as the main film-forming material for the anti-corrosion coating. This step begins with the dehydration treatment of polyether diol a, where water is removed at 110-120℃ under vacuum conditions, reducing the water content of polyether diol b to below 0.05%. This operation reduces subsequent side reactions between isocyanate and water. Subsequently, under nitrogen protection, the dehydrated polyether diol b is reacted with isophorone diisocyanate at 80-85℃ for 2-3 hours to generate an isocyanate-terminated polyurethane prepolymer. Finally, the polyurethane prepolymer is grafted and copolymerized with a bisphenol A type initial epoxy resin at 90-100℃ for 2-3 hours to obtain the modified epoxy resin. In this process, the polyether segments of the polyurethane prepolymer are chemically bonded to the epoxy resin backbone, giving the modified epoxy resin both the adhesion of epoxy resin and the flexibility of polyurethane, providing the basic mechanical properties for the coating.

[0025] It is known that step S1 adjusts the mechanical properties of the resin matrix by controlling the ratio of polyurethane prepolymer to the initial epoxy resin and the reaction conditions. A 30-40% mass ratio of polyurethane prepolymer can introduce flexible segments while maintaining the rigidity of the epoxy resin main chain, thereby improving the toughness of the modified epoxy resin compared to the initial epoxy resin. The dehydration process reduces the residual moisture in polyether diol a, thus reducing the possibility of isocyanate reacting with water to form urea-based byproducts, which is beneficial to the regularity of the polyurethane prepolymer's molecular structure. When using modified epoxy resin as a film-forming substance in coatings, it must possess good mechanical integrity and adhesion to the metal substrate to withstand volume shrinkage during curing and external forces during subsequent use, and to provide a matrix-supporting environment for the introduction of functional fillers.

[0026] Understandably, the modified epoxy resin prepared in step S1 provides the matrix conditions for the subsequent dispersion and interfacial bonding of modified graphene. If the resin matrix lacks sufficient toughness, the curing shrinkage stress will cause microcracks in the anti-corrosion coating. These defects will become channels for the penetration of corrosive media, weakening the anti-corrosion effect. The polyurethane segments introduced in step S1 can reduce the curing shrinkage stress of the resin and reduce the possibility of microcrack formation. At the same time, the residual active groups such as hydroxyl and epoxy groups in the modified epoxy resin help to enhance the interfacial bonding between the modified graphene and the modified epoxy base resin. Therefore, step S1, by optimizing the mechanical properties of the resin matrix and retaining active groups, provides favorable conditions for subsequently solving the problems of graphene dispersion and interfacial bonding.

[0027] It is worth noting that the selection of the temperature (110-120℃) and vacuum degree (-0.08)-(-0.1) MPa at the dehydration stage in step S1 can effectively remove moisture while reducing the risk of thermo-oxidative degradation of polyether diol. The isocyanate to hydroxyl molar ratio of (2.0-2.2):1 allows the polyurethane prepolymer to be end-capped with isocyanate groups, providing reactive sites for subsequent grafting of epoxy resin. Adding the polyurethane prepolymer to the initial epoxy resin at a time of 1-1.5 hours reduces the possibility of excessively high local concentrations leading to uncontrolled reaction rates. Maintaining the reaction temperature of 90-100℃ for 2-3 hours in system b allows for sufficient reaction between the isocyanate groups and the hydroxyl groups on the epoxy resin. The disappearance of the characteristic peak of the isocyanate group can be monitored by infrared spectroscopy to determine the reaction progress. The synergistic effect of these process parameters helps to obtain a modified epoxy resin with a relatively well-defined structure and stable performance, providing a technological basis for the reproducibility and large-scale production of coating formulations.

[0028] Specifically, in step S2, the dispersion containing graphene oxide a is subjected to initial graft modification to obtain graphene oxide b; then the graphene oxide b is subjected to further graft modification and post-processing to obtain modified graphene. Step S2 specifically includes the following steps: Step S21: Add graphene oxide a to the mixed solvent and use ultrasound to treat the mixed solvent intermittently (3 seconds working, 2 seconds rest) for 30-60 minutes. Then add glacial acetic acid to the mixed solvent to obtain a dispersion. In step S21, the graphene oxide a has a sheet diameter of 5-10 μm, a thickness of 1-3 nm, and an oxygen content of 35-40%. The mixed solvent includes ethanol and water in a volume ratio of 80:20, and the dispersion has a pH of 4.0-5.0 and a solid content of 0.5-1.0 wt%. Step S22: Hexadecyltrimethoxysilane and ethanol are stirred to obtain mixture a. Under stirring, mixture a is added dropwise to a dispersion at 60-65℃ within 30-45 min, and the mixture is stirred and reacted for 4-5 h to obtain system c containing graphene oxide b. In step S22, the mass of hexadecyltrimethoxysilane is 20-30% of the mass of graphene oxide a; the volume ratio of hexadecyltrimethoxysilane to ethanol is 1:(2-3). Step S23: KH560 (γ-glycidyl etheroxypropyltrimethoxysilane) is stirred with ethanol to obtain mixture b. Mixture b is added dropwise to system c at 60-65℃ over 20-30 min under stirring and stirred for 2-3 h to obtain system d containing graphene oxide c. In step S23, the mass of KH560 is 10-20% of the mass of graphene oxide a, and the volume ratio of KH560 to ethanol is 1:(2-3). Step S24: Centrifuge system d at 8000-10000 rpm for 15-20 min to obtain a separated solid (wet graphene oxide c). Then, wash the separated solid with anhydrous ethanol by centrifugation multiple times to obtain graphene oxide c. Dry the graphene oxide c at 60-70℃ and -0.09 MPa vacuum for 12-24 h, and then grind and sieve it to obtain modified graphene.

[0029] In step S24, the mesh size of the sieve is 200-250.

[0030] It should be noted that step S2 aims to modify the surface of graphene oxide a through double silanization grafting, thereby improving the dispersibility of graphene oxide a in the modified epoxy resin and its interfacial bonding with the modified epoxy resin. Specifically, graphene oxide a is first added to a mixed solvent, ultrasonically dispersed, and the pH is adjusted to 4.0-5.0 with glacial acetic acid to obtain a uniform dispersion. Subsequently, hexadecyltrimethoxysilane is added dropwise to the dispersion at 60-65℃ and reacted for 4-5 hours. The long-chain alkyl silane in hexadecyltrimethoxysilane hydrolyzes and condenses with the hydroxyl groups on the surface of graphene oxide a to obtain long-chain alkyl-grafted graphene oxide b. Next, KH560 is added dropwise to system c at the same temperature and reacted for 2-3 hours. The epoxy silane in KH560 is also grafted onto the surface of graphene oxide b to obtain graphene oxide c. Finally, graphene oxide c is centrifuged, washed, vacuum dried, ground, and sieved to obtain modified graphene powder. In this process, long-chain alkyl and epoxy segments are covalently linked to the surface of graphene sheets, thereby significantly improving the dispersion stability of modified graphene in organic solvents. Furthermore, the surface is covered with reactive epoxy groups. In addition, while introducing organic segments into the graphene surface through double silanization modification, the intrinsic two-dimensional sheet structure and conjugated network of graphene are not destroyed. Therefore, the modified graphene retains the original thermal and electrical conductivity properties of graphene.

[0031] It is understood that step S2, through initial grafting modification and subsequent grafting modification, sequentially grafts long-chain alkylsilanes and epoxy silanes, endowing the modified graphene with multiple functions. After grafting, the long-chain alkyl groups form a steric hindrance layer on the graphene surface, effectively preventing the graphene sheets from agglomerating due to van der Waals forces. Simultaneously, the hydrophobicity of the alkyl chains constructs a nanoscale hydrophobic barrier on the graphene surface, delaying the penetration of water molecules to the interface. Grafting with epoxy silanes provides graphene with active epoxy groups that can participate in the resin crosslinking reaction, enabling them to chemically bond with the hydroxyl, amino, and other groups in the modified epoxy resin prepared in step S1. This allows the modified graphene to be uniformly dispersed in the resin matrix and form a continuous barrier network. Furthermore, chemical anchoring enhances the interfacial bonding force with the matrix, thereby fully utilizing the physical barrier properties of graphene and preventing the degradation of anti-corrosion performance due to agglomeration or interfacial defects.

[0032] Understandably, the modified graphene obtained in step S2 can solve the problems of poor graphene dispersion stability and weak interfacial bonding. Through the steric hindrance effect of long-chain alkyl groups, the modified graphene sheets can remain in an exfoliated state in the solvent and modified epoxy resin, avoiding the loss of effective specific surface area and discontinuous barrier structure caused by agglomeration. The grafted epoxy groups enable the modified graphene to participate as a reactive filler in the cross-linking and curing of the anti-corrosion coating, anchoring it in the three-dimensional network of the modified epoxy resin through chemical bonds, solving the problem of insufficient interfacial bonding in physical blend systems and reducing the formation of micropores and defects. Furthermore, the introduction of the hydrophobic alkyl layer further increases the resistance to water molecule penetration, and together with the synergistic barrier effect of the functional fillers in subsequent steps, it enhances the long-term anti-corrosion performance of the coating.

[0033] It is worth noting that the acidic conditions of the dispersion (pH 4.0-5.0) in step S2 catalyze the hydrolysis of silane to generate silanol, while simultaneously inhibiting silanol self-condensation and promoting the condensation reaction between silanol and the hydroxyl groups on the surface of graphene oxide a. The hexadecyltrimethoxysilane, at 20-30% of the mass of graphene oxide a, forms a sufficiently dense alkyl chain on the graphene surface to provide effective steric hindrance while preventing excessive silane self-polymerization. The KH560, at 10-20% of the mass of graphene oxide a, ensures sufficient reactive sites while preventing excessive epoxy groups that could decrease storage stability. The reaction temperature of 60-65℃ and time of 4-5 h in step S22, and the reaction temperature of 60-65℃ and time of 2-3 h in step S23, ensure the grafting reaction proceeds fully and side reactions are controllable. Centrifugation at 8000-10000 rpm and multiple washings effectively remove unreacted silane and byproducts, while vacuum drying at 60-70℃ prevents epoxy ring-opening at high temperatures. The synergistic effect of the above process parameters ensures that the modified graphene has a clear structure and stable properties, providing a quality-controllable modified filler for subsequent composite with the modified epoxy resin in step S1.

[0034] Specifically, in step S3, a slurry containing modified graphene is prepared, and the slurry is mixed with functional fillers to obtain a composite slurry; Step S3 specifically includes the following steps: Step S31: Add the modified graphene to the butyl acetate solvent and disperse at 1500-2000 rpm for 30-45 min to obtain a slurry; In step S31, the solid content of the slurry is 5-8 wt%; Step S32: Add the organically modified montmorillonite to the slurry and disperse it at a speed of 2000-2500 rpm for 20-30 minutes, then perform ultrasonic degassing treatment for 10-15 minutes to obtain the composite slurry.

[0035] In step S32, the sheet diameter of the organically modified montmorillonite is 200-500 nm, and the mass ratio of the organically modified montmorillonite to the modified graphene is (25-30):(70-75).

[0036] It should be noted that step S3 aims to uniformly blend modified graphene and organically modified montmorillonite (the grade of organically modified montmorillonite is DK4) in a solvent to form a stable composite slurry. Specifically, modified graphene powder is first added to butyl acetate solvent and dispersed at 1500-2000 rpm for 30-45 min to obtain a modified graphene slurry with a solid content of 5-8 wt%. During this process, the long-chain alkyl groups on the surface of the modified graphene extend in the butyl acetate solvent, providing steric hindrance, allowing the modified graphene sheets to be exfoliated and stably suspended. Subsequently, organically modified montmorillonite with a sheet diameter of 200-500 nm is added to the slurry and dispersed at 2000-2500 rpm for 20-30 min to further mix the two fillers. The mixture is then subjected to ultrasonic degassing for 10-15 min to obtain the composite slurry. In this process, the modified graphene micron-sized sheets and montmorillonite submicron-sized sheets interweave and are evenly distributed in butyl acetate solvent, so that the composite slurry presents a delicate, particle-free viscous liquid state, laying the foundation for subsequent mixing with modified epoxy resin.

[0037] It is known that step S3, through a two-step dispersion process and corresponding material ratios, achieves uniform blending of modified graphene and organically modified montmorillonite in butyl acetate solvent. The long-chain alkyl groups on the surface of the modified graphene provide steric hindrance, enabling it to disperse stably in butyl acetate without agglomeration. The organically modified montmorillonite, after organic treatment, also exhibits good compatibility with the solvent. The composite slurry formed after the dispersion of the two fillers allows the modified graphene and organically modified montmorillonite sheets to form a stable mixed system in butyl acetate solvent, avoiding localized agglomeration during subsequent mixing with modified epoxy resin. Simultaneously, the difference in sheet size between the two fillers constructs a multi-scale filler network prototype, with large-sized modified graphene sheets forming the main barrier framework and small-sized montmorillonite sheets filling the gaps in the framework. Therefore, after the composite slurry is mixed with and cured with modified epoxy resin, the resulting anti-corrosion coating can form a denser, more tortuous physical barrier structure, significantly extending the penetration path of corrosive media. In addition, the modified graphene is uniformly dispersed in the slurry and the layers maintain an appropriate spacing, which lays the foundation for the formation of interconnected thermal and electrical conductive pathways in the subsequent cured coating.

[0038] Understandably, the composite slurry obtained in step S3 provides a crucial pre-dispersion of filler to address the issues of poor graphene dispersion stability and insufficient anti-corrosion performance. Although step S2 has already surface-modified the graphene, directly adding it in powder form to high-viscosity modified epoxy resin may still lead to localized agglomeration due to poor wetting or insufficient shear force. Step S3 first disperses the modified graphene in butyl acetate solvent to prepare a slurry, ensuring that the modified graphene sheets are fully exfoliated and stably exist. Then, it is blended with organically modified montmorillonite, further enhancing the uniformity of filler dispersion. Uniformly dispersed graphene can effectively construct a labyrinth effect in the anti-corrosion coating, exerting a physical barrier function. The introduction of organically modified montmorillonite not only compensates for the microscopic gaps between the single modified graphene sheets but also increases the density and impermeability of the anti-corrosion coating. Furthermore, after the two fillers in the composite slurry are subsequently mixed with the modified epoxy resin in step S1, the epoxy groups on the surface of the modified graphene can undergo chemical cross-linking with the modified epoxy resin, while the organic modified montmorillonite exists in the network through physical dispersion. The two work together to enhance the integrity and interfacial bonding of the anti-corrosion coating, thereby jointly solving the problem that the anti-corrosion performance is difficult to effectively exert.

[0039] It is worth noting that in step S3, the modified graphene is dispersed separately in butyl acetate with a solid content controlled at 5-8 wt%. This ensures that the slurry has a certain filler content to facilitate subsequent paint formulation, while avoiding excessive viscosity that would lead to dispersion difficulties. Dispersion at 1500-2000 rpm for 30-45 minutes utilizes shear force to break up any slight agglomerates that may exist in the modified graphene, while the steric hindrance of long-chain alkyl groups maintains dispersion stability. Subsequently, organically modified montmorillonite is added and the speed is increased to 2000-2500 rpm for 20-30 minutes. This aims to allow the small-sized montmorillonite sheets to fully insert between the graphene sheets, forming a uniform mixed network. Ultrasonic degassing treatment eliminates the microbubbles introduced by high-speed dispersion, preventing pinhole defects from forming after the anti-corrosion coating has cured. The mass ratio of modified graphene to montmorillonite (70-75):(25-30) ensures both a highly efficient barrier network dominated by modified graphene and enhanced density by effectively filling gaps with modified montmorillonite. Furthermore, the lower cost of organically modified montmorillonite reduces economic costs. The synergistic effect of these process parameters ensures the quality stability and repeatability of the composite slurry, providing a reliable filler intermediate for the subsequent preparation of high-performance anti-corrosion coatings.

[0040] Specifically, in step S4, the modified epoxy resin is mixed with the composite slurry to obtain the main agent; before coating, the main agent is mixed with the curing agent to form a coating, and then the coating is applied to the substrate for curing to obtain an anti-corrosion coating.

[0041] Step S4 specifically includes the following steps: Step S41: Stir the modified epoxy resin, composite slurry, leveling agent (BYK-358N) and defoamer (BYK-066N) at 800-1000 rpm for 20-30 min to obtain a mixture, and then mix the mixture with butyl acetate to obtain the main agent; In step S41, the modified epoxy resin, composite slurry, leveling agent and defoamer are 70-85 parts by weight, 10-25 parts by weight, 0.5-1.0 parts by weight and 0.2-0.5 parts by weight, respectively, and are adjusted with butyl acetate to make the total weight of the main agent 100 parts by weight. Step S42: Before coating, mix the main agent and the curing agent and stir at 600-800 rpm for 3-5 minutes to obtain the coating; use air spraying method to spray the coating onto the substrate surface with a spraying pressure of 0.4-0.6 MPa through a nozzle with a diameter of 1.5-2.0 mm to form a wet film. In step S42, the mass ratio of the main agent to the curing agent is 100:(15-25), and the curing agent is a polyurethane curing agent, with a wet film thickness of 120-220 μm. Step S43: After curing the substrate with the film layer at 60°C for 24 hours, it is naturally cooled to room temperature to obtain the anti-corrosion coating.

[0042] In step S43, the thickness of the anti-corrosion coating is 80-120 μm.

[0043] It should be noted that step S4 aims to mix the modified epoxy resin, composite slurry, additives, and curing agent to form the final anti-corrosion coating through application and curing. Specifically, 70-85 parts by weight of modified epoxy resin, 10-25 parts by weight of composite slurry, 0.5-1.0 parts by weight of leveling agent, and 0.2-0.5 parts by weight of defoamer are first stirred at 800-1000 rpm for 20-30 minutes, and then adjusted to a total weight of 100 parts by weight with butyl acetate to obtain the main agent. At this point, the modified graphene and montmorillonite in the composite slurry are uniformly dispersed in the modified epoxy resin, and the epoxy groups on the surface of the modified graphene are in a physically mixed state with the active groups in the modified epoxy resin. Before coating, the main agent and polyurethane curing agent are stirred at 600-800 rpm for 3-5 minutes to obtain the coating. The isocyanate groups of the polyurethane curing agent begin to react with the hydroxyl groups in the modified epoxy resin and the epoxy groups on the surface of the modified graphene. The coating was then applied to the substrate surface using an air spraying method, forming a wet film with a thickness of 120-220 μm. It was then cured at 60°C for 24 hours, allowing the solvent in the wet film to evaporate and the cross-linking reaction to proceed fully, ultimately forming an anti-corrosion coating with a thickness of 80-120 μm. In this process, modified graphene undergoes chemical cross-linking with the polyurethane curing agent and modified epoxy resin through its surface epoxy groups, anchoring itself in a three-dimensional network. Organically modified montmorillonite is uniformly distributed in the network gaps, thus forming a continuous, dense solid film, i.e., the anti-corrosion coating.

[0044] It is understood that step S4, through the mixing of the main agent and the polyurethane curing agent and the application of the coating, achieves the transformation of the anti-corrosion coating from a liquid mixture to a solid cross-linked network. Under the above treatment, on the one hand, the epoxy groups on the surface of the modified graphene participate in the cross-linking reaction, anchoring the modified graphene in the resin network through chemical bonds; on the other hand, the two sheet fillers in the composite slurry form a physical barrier network during the curing process; in addition, the curing temperature and time allow the cross-linking reaction to proceed fully, allowing the solvent to evaporate completely. The graphene modified by double silanization in step S2 retains its intrinsic two-dimensional sheet structure and conjugated network. In the cross-linked network formed in step S4, the uniformly dispersed and overlapping modified graphene sheets construct continuous thermal and electrical conductive pathways within the anti-corrosion coating, giving the anti-corrosion coating certain thermal and electrical conductivity functions. Under the action of step S4, chemical anchoring ensures the bonding strength between the modified graphene and the modified epoxy resin interface, avoiding the formation of penetration channels due to interface defects; the formed physical barrier network extends the penetration path of corrosive media; and full curing ensures the density and mechanical properties of the anti-corrosion coating, so that the anti-corrosion function can be stably performed.

[0045] Understandably, the technical effect achieved in step S4 directly addresses the problems of poor graphene dispersion stability and weak interfacial bonding. Specifically, modified graphene participates in the cross-linking reaction through surface epoxy groups, anchoring itself in the resin network via chemical bonds. This changes the interfacial state of traditional physical blending, which relies solely on van der Waals forces or hydrogen bonds, thus solving the problem of insufficient interfacial bonding and reducing the formation of micropores and defects. The modified graphene and montmorillonite in the composite slurry form a multi-scale physical barrier network during curing, which, together with the hydrophobic alkyl layer introduced in step S2, significantly extends the penetration paths of moisture, oxygen, and corrosive ions, effectively solving the problem of discontinuous barrier structures caused by uneven graphene dispersion. Furthermore, the polyurethane segments in the modified epoxy resin prepared in step S1 buffer the volume shrinkage stress during curing, further reducing the probability of defects in the anti-corrosion coating. In addition, the continuous thermal and electrical conductive pathways constructed by modified graphene in the anti-corrosion coating enable the anti-corrosion coating to have heat dissipation and anti-static functions, which can avoid damage to the anti-corrosion coating and substrate caused by heat accumulation or electrostatic discharge, and further improve the overall protective performance of the coating.

[0046] It is worth noting that the ratio of 70-85 parts by weight of modified epoxy resin to 10-25 parts by weight of composite slurry in step S4 ensures sufficient barrier effect while avoiding viscosity increase and defect risk caused by high filler content. The mass ratio of main agent to curing agent is 100:(15-25), ensuring moderate crosslinking density and giving the anti-corrosion coating both hardness and toughness. Stirring speeds of 800-1000 rpm and 600-800 rpm ensure uniform mixing of components while avoiding the introduction of excessive air bubbles. Spraying pressure of 0.4-0.6 MPa and nozzle diameter of 1.5-2.0 mm ensure good atomization of the coating, forming a uniform wet film. A wet film thickness of 120-220 μm ensures that the thickness of the anti-corrosion coating after solvent evaporation is 80-120 μm, providing sufficient protective thickness. Curing at 60℃ for 24 hours allows the isocyanate groups to fully react with the hydroxyl and epoxy groups, while avoiding damage to the substrate or anti-corrosion coating from high temperatures. The synergistic effect of the above process parameters ensures that the anti-corrosion coating forms a stable cross-linked structure and a dense physical network.

[0047] The present invention also provides a graphene-based anti-corrosion coating, which is prepared by the above preparation method, as detailed in Examples 1, 2 and 3.

[0048] Example 1: Step S1: Polyether diol a is added to a reaction vessel and dehydrated for 1.8 h at 115°C and a vacuum of -0.09 MPa to obtain polyether diol b with a water content of 0.03%. The reaction vessel is then cooled to 55°C, and isophorone diisocyanate is added to the reaction vessel, controlling the molar ratio of isocyanate groups to hydroxyl groups to be 2.1:1. Then, system a is heated to 82°C and reacted for 2.5 h under nitrogen protection. The isocyanate group content is measured every 30 min. The reaction is stopped when the isocyanate group content reaches 9.0% of the mass of system a, yielding an isocyanate-terminated polyurethane prepolymer. Bisphenol A type epoxy resin was heated to 85°C in a reaction vessel. Under stirring, polyurethane prepolymer was added dropwise to the reaction vessel over 1.2 hours. The mass ratio of polyurethane prepolymer to epoxy resin was 35:65. After the addition was completed, system b was heated to 95°C and reacted for 2.5 hours to obtain polyurethane modified epoxy resin.

[0049] Step S2: Graphene oxide a with a diameter of 8 μm, a thickness of 2 nm, and an oxygen content of 38% was added to a mixed solvent of ethanol and water. The mixture was subjected to intermittent ultrasonic treatment at a power of 650 W for 45 min. Glacial acetic acid was then added to adjust the pH to 4.5, resulting in a dispersion with a solid content of 0.8 wt%. Hexadecyltrimethoxysilane, weighing 25% of the mass of graphene oxide, was mixed with ethanol at a volume ratio of 1:2.5 and stirred to obtain mixture a. While stirring, mixture a was added dropwise to the dispersion at 62°C over 35 min. The mixture was stirred at 62°C for 4.5 h to obtain system c containing graphene oxide b. Weigh KH560, which accounts for 15% of the mass of graphene oxide, and mix it with ethanol at a volume ratio of 1:2.5 to obtain mixture b. While stirring, mixture b is added dropwise to system c at 62℃ over 25 minutes. The mixture is stirred at 62℃ for 2.5 hours to obtain system d containing graphene oxide c. System d is centrifuged at 9000 rpm for 18 minutes to obtain a separated solid. The separated solid is washed three times with anhydrous ethanol by centrifugation to obtain graphene oxide c. Graphene oxide c is dried at 65℃ under a vacuum of -0.09 MPa for 18 hours and then ground through a 220-mesh sieve to obtain modified graphene.

[0050] Step S3: Add modified graphene to butyl acetate solvent and disperse at 1800 rpm for 35 min to obtain a slurry with a solid content of 6.5 wt%. Add organically modified montmorillonite with a sheet diameter of 350 nm to the slurry, with a mass ratio of organically modified montmorillonite to modified graphene of 28:72; disperse at 2200 rpm for 25 min, and then perform ultrasonic degassing treatment for 12 min to obtain a composite slurry.

[0051] Step S4: By weight, add 78 parts of modified epoxy resin, 18 parts of composite slurry, 0.8 parts of leveling agent, and 0.3 parts of defoamer to a paint mixing tank and stir at 900 rpm for 25 minutes. Then, adjust the total weight of the main agent to 100 parts by weight with butyl acetate to obtain the main agent. Before coating, mix the main agent and polyurethane curing agent at a mass ratio of 100:20 and stir at 700 rpm for 4 minutes to obtain the coating. Using an air spraying method, spray the coating onto the surface of a carbon steel substrate that has been sandblasted to Sa2.5 grade at a spraying pressure of 0.5 MPa through a nozzle with a diameter of 1.8 mm to form a wet film with a thickness of 180 μm. Place the carbon steel substrate with the wet film in a 60℃ forced-air drying oven for curing for 24 hours, and then allow it to cool naturally to room temperature to obtain a dry film thickness of 100 μm for the anti-corrosion coating.

[0052] Example 2: The basic content is the same as in Example 1, except that: In step S2, the mass of hexadecyltrimethoxysilane is 20% of the mass of graphene oxide, and the reaction time is 4 hours; the mass of KH560 is 10% of the mass of graphene oxide, and the reaction time is 2 hours.

[0053] Step S3: Add modified graphene to butyl acetate solvent and disperse at 1800 rpm for 35 min to obtain a slurry with a solid content of 5.0 wt%; the mass ratio of organic modified montmorillonite to modified graphene is 25:75.

[0054] Step S4: By weight, 82 parts of modified epoxy resin and 12 parts of composite slurry are adjusted to 100 parts by weight of the total weight of the main agent using butyl acetate.

[0055] Example 3: The basic content is the same as in Example 1, except that: In step S2, the mass of hexadecyltrimethoxysilane is 30% of the mass of graphene oxide, and the reaction time is 5 hours; the mass of KH560 is 20% of the mass of graphene oxide, and the reaction time is 3 hours.

[0056] Step S3: Add modified graphene to butyl acetate solvent and disperse at 1800 rpm for 35 min to obtain a slurry with a solid content of 8.0 wt%; the mass ratio of organic modified montmorillonite to modified graphene is 30:70.

[0057] Step S4: By weight, 72 parts of modified epoxy resin and 24 parts of composite slurry are adjusted to 100 parts by weight of the total weight of the main agent using butyl acetate.

[0058] Comparative Example 1: The basic content is the same as in Example 1, except that: In Comparative Example 1, the graphene oxide powder was not modified, and untreated graphene was used.

[0059] Comparative Example 2: The basic content is the same as in Example 1, except that: In Comparative Example 2, only graphene oxide a was grafted with KH560, without hexadecyltrimethoxysilane grafting; and KH560 was added dropwise to the dispersion at an amount of 15% of the mass of graphene oxide a, and the reaction was carried out for 2.5 h.

[0060] The following is a comparison of the performance of Examples 1, 2, and 3 with Comparative Examples 1 and 2, as shown in Table 1: Table 1: In the above test items, the coating appearance was tested according to GB / T 1729-1979, the adhesion according to GB / T5210-2006, the impact resistance according to GB / T 1732-2020, the salt spray resistance according to GB / T 1771-2007, and the water vapor transmission rate according to GB / T 1037-2021.

[0061] As shown in Table 1, Example 1 exhibits excellent and balanced performance across all aspects, with an adhesion of 8.5 MPa, satisfactory impact resistance, a salt spray life of 2100 h, and a water vapor transmission rate of 0.85, indicating a good synergistic effect between the dual silanization modification and the appropriate filler ratio. Example 2, due to its lower silane grafting rate and filler content, suffers from slightly insufficient dispersibility and interfacial bonding, achieving a salt spray life of 1650 h and a water vapor transmission rate of 1.20, which is lower than Example 1 but still significantly better than Comparative Examples 1 and 2. Example 3, with its higher silane grafting rate and filler content, forms a denser barrier network, achieving a salt spray life of 2300 h, a water vapor transmission rate of only 0.72, and the highest adhesion of 9.2 MPa, indicating that appropriately increasing the filler and grafting rate helps improve performance. Comparative Example 1: The coating has a rough appearance, obvious agglomeration, low adhesion (4.2 MPa), poor impact resistance, a salt spray life of only 550 h, and a water vapor transmission rate as high as 3.80, confirming that unmodified graphene cannot provide effective corrosion protection. Comparative Example 2: Modification with KH560 alone was an improvement over the unmodified version (1250h salt spray), but the lack of steric hindrance and hydrophobic barrier of long-chain alkyl groups resulted in dispersion stability and interfacial bonding that were still inferior to the dual-modification scheme (Examples 1-3). The salt spray lifetime was reduced by about 40% compared to Example 1.

[0062] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a graphene-based anti-corrosion coating, characterized in that, The preparation method includes the following steps: Step S1: Graft copolymerize the polyurethane prepolymer with a flexible polyether backbone with the initial epoxy resin to obtain the modified epoxy resin. Step S2: The dispersion containing graphene oxide a is subjected to initial graft modification to obtain graphene oxide b; then the graphene oxide b is subjected to further graft modification and post-processing to obtain modified graphene. Step S3: Prepare a slurry containing modified graphene, and mix the slurry with functional fillers to obtain a composite slurry; Step S4: Mix the modified epoxy resin with the composite slurry to obtain the main agent; before coating, mix the main agent with the curing agent to form a coating, then apply the coating to the substrate for curing to obtain an anti-corrosion coating.

2. The method for preparing the graphene-based anti-corrosion coating according to claim 1, characterized in that, Step S1 specifically includes the following steps: Step S11: Add polyether diol a to a reaction vessel and dehydrate it at a temperature of 110-120℃, a vacuum degree of (-0.08)-(-0.1) MPa, and a time of 1.5-2h to obtain polyether diol b; Step S12: Cool system a in the reactor to 50-60℃, add isophorone diisocyanate to the reactor, then heat system a to 80-85℃ and react under nitrogen for 2-3 hours to obtain polyurethane prepolymer. Step S13: The initial bisphenol A type epoxy resin is heated to 80-90℃ in the reaction vessel, and the polyurethane prepolymer is added dropwise to the reaction vessel over 1-1.5 hours while stirring. After the dropwise addition is completed, the system b in the reaction vessel is heated to 90-100℃ and reacted for 2-3 hours to obtain the modified epoxy resin.

3. The method for preparing the graphene-based anti-corrosion coating according to claim 2, characterized in that, In step S11, the water content of the polyether diol b is ≤0.05%; In step S12, the molar ratio of isocyanate groups to hydroxyl groups in the isophorone diisocyanate is (2.0-2.2):1; during the reaction, the isocyanate group content of system a is measured every 30 minutes, and the reaction progress is tracked by the di-n-butylamine method until the isocyanate group content reaches 8.5-9.5% of system a, and then the reaction is stopped. In step S13, the mass ratio of the polyurethane prepolymer to the initial epoxy resin is (30-40):(60-70).

4. The method for preparing the graphene-based anti-corrosion coating according to claim 1, characterized in that, Step S2 specifically includes the following steps: Step S21: Add graphene oxide a to the mixed solvent and use ultrasound to intermittently sonicate the mixed solvent with a power of 500-800W for 30-60min. Then add glacial acetic acid to the mixed solvent to obtain a dispersion. Step S22: Hexadecyltrimethoxysilane and ethanol are stirred to obtain mixture a. Under stirring, mixture a is added dropwise to a dispersion at 60-65℃ within 30-45 min, and the mixture is stirred and reacted for 4-5 h to obtain system c containing graphene oxide b. Step S23: KH560 and ethanol are stirred to obtain mixture b. Mixture b is added dropwise to system c at 60-65℃ under stirring for 20-30 min and stirred for 2-3 h to obtain system d containing graphene oxide c. Step S24: Centrifuge system d at 8000-10000 rpm for 15-20 min to obtain a separated solid. Then, wash the separated solid with anhydrous ethanol by centrifugation multiple times to obtain graphene oxide c. Dry graphene oxide c at 60-70℃ and -0.09 MPa vacuum for 12-24 h, and then grind and sieve it to obtain modified graphene.

5. The method for preparing the graphene-based anti-corrosion coating according to claim 4, characterized in that, In step S21, the graphene oxide a has a sheet diameter of 5-10 μm, a thickness of 1-3 nm, and an oxygen content of 35-40%. The mixed solvent includes ethanol and water in a volume ratio of 80:

20. The dispersion has a pH of 4.0-5.0 and a solid content of 0.5-1.0 wt%. In step S22, the mass of the hexadecyltrimethoxysilane is 20-30% of the mass of graphene oxide a; the volume ratio of the hexadecyltrimethoxysilane to ethanol is 1:(2-3). In step S23, the mass of KH560 is 10-20% of the mass of graphene oxide a, and the volume ratio of KH560 to ethanol is 1:(2-3). In step S24, the mesh size of the sieve is 200-250.

6. The method for preparing the graphene-based anti-corrosion coating according to claim 1, characterized in that, Step S3 specifically includes the following steps: Step S31: Add the modified graphene to the butyl acetate solvent and disperse at 1500-2000 rpm for 30-45 min to obtain a slurry; Step S32: Add the organically modified montmorillonite to the slurry and disperse it at a speed of 2000-2500 rpm for 20-30 minutes, then perform ultrasonic degassing treatment for 10-15 minutes to obtain the composite slurry.

7. The method for preparing the graphene-based anti-corrosion coating according to claim 6, characterized in that, In step S31, the solid content of the slurry is 5-8 wt%. In step S32, the sheet diameter of the organic modified montmorillonite is 200-500 nm, and the mass ratio of the organic modified montmorillonite to the modified graphene is (25-30):(70-75).

8. The method for preparing a graphene-based anti-corrosion coating according to claim 1, characterized in that, Step S4 specifically includes the following steps: Step S41: Stir the modified epoxy resin, composite slurry, leveling agent and defoamer at 800-1000 rpm for 20-30 min to obtain a mixture, and then mix the mixture with butyl acetate to obtain the main agent; Step S42: Before coating, mix the main agent and the curing agent and stir at 600-800 rpm for 3-5 minutes to obtain the coating; use air spraying method to spray the coating onto the substrate surface with a spraying pressure of 0.4-0.6 MPa through a nozzle with a diameter of 1.5-2.0 mm to form a wet film. Step S43: After curing the substrate with the film layer at 60°C for 24 hours, it is naturally cooled to room temperature to obtain the anti-corrosion coating.

9. The method for preparing the graphene-based anti-corrosion coating according to claim 8, characterized in that, In step S41, the modified epoxy resin, composite slurry, leveling agent and defoamer are 70-85 parts by weight, 10-25 parts by weight, 0.5-1.0 parts by weight and 0.2-0.5 parts by weight, respectively, and are adjusted with butyl acetate to a total weight of 100 parts by weight. In step S42, the mass ratio of the main agent to the curing agent is 100:(15-25), and the curing agent is a polyurethane curing agent, and the thickness of the wet film is 120-220μm; In step S43, the thickness of the anti-corrosion coating is 80-120 μm.

10. A graphene-based anti-corrosion coating, characterized in that, The graphene-based anti-corrosion coating is prepared using the method described in any one of claims 1-9.

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