Marine steel structure water-based anticorrosive paint based on graphene modification and preparation method of marine steel structure water-based anticorrosive paint

Abstract

The invention belongs to the technical field of anticorrosive paint preparation, and provides a graphene modification-based marine steel structure water-based anticorrosive paint and a preparation method thereof. Polyaniline nanofibers are prepared from aniline, ammonium persulfate and p-toluenesulfonic acid, and ammonium orthomolybdate is used for modification; the preparation method comprises the following steps: carrying out silanization modification on SiO2 nano powder by adopting GPTMS, and compounding with modified polyaniline nano fibers, so as to obtain a PANI-SiO2 composite material; the preparation method comprises the following steps: preparing nitrogen and sulfur co-doped graphene through heat treatment of thiourea and urea, and realizing intercalation and silanization modification of graphene by using an intercalator and KH560; the preparation method comprises the following steps: preparing a fluorine-containing segment prepolymer and a multifunctional copolymer segment, and preparing a functionalized emulsion by using a tetrathiol cross-linking agent; the preparation method comprises the following steps: sequentially adding silane modified graphene, a PANI-SiO2 composite material and a functional emulsion into a water-based epoxy resin system, and matching with a flatting agent, a defoaming agent and a thickening agent to obtain the water-based anticorrosive paint suitable for the marine steel structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-corrosion coating preparation, and relates to a waterborne anti-corrosion coating for marine steel structures modified by graphene and a preparation method thereof. Background Art

[0002] With the increasing frequency of marine development activities, the extensive application of steel structures in marine engineering has made their corrosion problems more prominent. Seawater contains high concentrations of chloride ions, dissolved oxygen, salts, and other corrosive substances. The combined action of these factors leads to the accelerated corrosion of marine metal structures. Seawater is a highly conductive electrolyte, and metal structures are prone to electrochemical corrosion in seawater, which makes the corrosion problem of marine steel structures extremely prominent. Seawater erosion-corrosion is the result of the combination of mechanical erosion and chemical corrosion, and usually occurs in parts of marine structures subjected to high-speed ocean currents, waves, or tides. The high-speed seawater flow exerts shear stress on the metal surface, damaging the passive film or protective coating and exposing the unprotected metal surface. The erosion action exposes fresh metal to the corrosive environment and at the same time removes corrosion products (such as rust), enabling the corrosion process to continue. Seawater erosion can mechanically damage the passive film or corrosion product layer on the metal surface, exposing the metal to the corrosive environment and significantly increasing the rate of electrochemical corrosion. Moreover, the erosion action can remove corrosion products (such as rust or oxides) and prevent the re-deposition of the products, and this removal action further accelerates the metal corrosion process.

[0003] At present, the anti-corrosion measures for marine steel structures mainly include coating protection, sacrificial anode protection, impressed current protection, etc. Coating protection is a commonly used method. By coating a layer of anti-corrosion paint on the metal surface, the metal is isolated from seawater, thus playing an anti-corrosion role. However, the traditional solvent-based anti-corrosion paints have certain limitations in terms of water resistance and adhesion. When used in the marine environment for a long time, phenomena such as bubbling and peeling are likely to occur, resulting in a decline in the anti-corrosion effect. Sacrificial anode protection is achieved by connecting a metal more active than the protected metal, such as magnesium, zinc, aluminum alloy, etc., in seawater. The active metal acts as an anode and corrodes, while the protected metal acts as a cathode and is protected. However, the consumption rate of the sacrificial anode material is not easy to control, and regular inspection and replacement are required. Waterborne paints have the advantages of being simple and easy to operate, fast drying speed, good leveling property, etc. during the construction process, which can improve the construction efficiency and reduce the construction cost, making waterborne paints have good application prospects in the field of marine steel structure anti-corrosion. As a new type of two-dimensional carbon nanomaterial, graphene has shown great application potential in the field of anti-corrosion coatings in recent years. Graphene has an ultra-high specific surface area and excellent barrier properties. Its lamellar structure can form a continuous and dense protective film in the coating, effectively preventing the penetration of corrosive media such as oxygen, water molecules, and chloride ions. At the same time, the interaction between graphene and the polymer matrix is good, and it can form a strong interfacial bond with the matrix material in the waterborne anti-corrosion coating, enhancing the adhesion of the coating. Therefore, it is of great significance to develop a waterborne anti-corrosion coating for marine steel structures based on graphene modification. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a waterborne anti-corrosion coating for marine steel structures based on graphene modification and its preparation method. First, polyaniline nanofibers are prepared by aniline oxidative polymerization and modified with ammonium orthomolybdate. At the same time, the surface of SiO2 nanopowder is modified with a silane coupling agent and compounded with the modified polyaniline to form a PANI-SiO2 composite material. Secondly, nitrogen and sulfur co-doped graphene is prepared by heat treatment with thiourea and urea, and further intercalation and silanization modification of graphene are realized by using an intercalating agent and KH560 to improve its dispersibility and interfacial bonding performance. Then, a fluorine-containing segment prepolymer and a multifunctional copolymer segment are prepared to obtain a functionalized emulsion, endowing the coating with excellent hydrophobic and corrosion-resistant properties. Finally, the silane-modified graphene, PANI-SiO2 composite material and functionalized emulsion are added to the waterborne epoxy resin system to prepare a waterborne anti-corrosion coating with excellent performance, so as to meet the needs of actual production.

[0005] To achieve this purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a preparation method of a waterborne anti-corrosion coating for marine steel structures based on graphene modification, and the preparation method includes: S1, Ice bath: Disperse aniline, p-toluenesulfonic acid and ammonium persulfate solution in deionized water while stirring. Wash and filter to obtain polyaniline nanofibers. Then immerse the polyaniline nanofibers in ammonium paramolybdate solution, stir well, centrifuge, wash and dry to obtain modified polyaniline nanofibers. Disperse SiO2 nanopowder and GPTMS in absolute ethanol, adjust to the first temperature, stir and reflux, filter, wash and vacuum dry to obtain modified SiO2. Disperse the modified polyaniline nanofibers and modified SiO2 in deionized water, adjust the temperature to the second temperature and adjust the pH to 7. Stir and react, then centrifuge, wash and freeze-dry to obtain PANI-SiO2; S2, Disperse graphene, thiourea and urea in deionized water, ultrasonically disperse and then transfer to a reaction kettle and adjust the temperature to the third temperature for reaction. After the reaction, wash the product with 1wt.% KOH solution and dry to obtain N,S co-doped graphene powder. Disperse the N,S co-doped graphene powder and an intercalating agent in N-methylpyrrolidone, adjust the temperature to the fourth temperature and stir. Filter, wash and dry to obtain a partially intercalated graphene material. Disperse the partially intercalated graphene material and KH560 in an ethanol aqueous solution, adjust the pH to 5 and adjust the temperature to the second temperature, reflux and react. After centrifuging, washing and drying, obtain silane-modified graphene powder; S3, Disperse trifluoroethyl methacrylate and azobisisobutyronitrile in dimethyl sulfoxide, adjust the temperature to the second temperature for reaction under a nitrogen atmosphere. After the reaction, add ethanol for separation to obtain a fluorine-containing segment prepolymer. Disperse N-vinylpyrrolidone, 3-(methacryloyloxy)propyltrimethoxysilane, maleic anhydride and azobisisobutyronitrile in dimethyl sulfoxide, adjust the temperature to the second temperature and stir for reaction under a nitrogen atmosphere. After the reaction, add ethanol for separation to obtain a multifunctional copolymer segment. Disperse the fluorine-containing segment prepolymer, multifunctional copolymer segment and pentaerythritol tetrakis(3-mercaptopropionate) in dimethyl sulfoxide, adjust the temperature to the fourth temperature and stir for reaction to obtain a macromolecular solution. Then disperse the macromolecular solution and Tween 80 in deionized water and stir, adjust the pH to 8 and adjust the temperature to 70 °C for heat preservation to obtain a functionalized emulsion; S4, Add a leveling agent, a defoaming agent and a thickening agent to waterborne epoxy resin in sequence and mix evenly. Then add the silane-modified graphene powder, the functionalized emulsion and PANI-SiO2 to the waterborne epoxy resin in sequence. After mixing evenly, add a curing agent during use to obtain a waterborne anti-corrosion coating for marine steel structures based on graphene modification.

[0006] The preparation of polyaniline uses aniline monomer as the starting material and ammonium persulfate as the oxidant to achieve chemical oxidative polymerization. Ammonium persulfate decomposes in aqueous solution to generate active oxidative species such as sulfate radicals. These radicals oxidize aniline monomer to generate aniline radical cations through an electron transfer mechanism. After the generation of radical cations, intermolecular coupling reactions drive the formation of linear polyaniline chains. By controlling the low-temperature environment under an ice-water bath, the radical reaction rate is effectively reduced, and unnecessary side reactions are inhibited, such as the formation of excessive cross-linking or branched chains. The low-temperature regulation can also limit the rapid growth of polyaniline chains, enabling them to gradually form fibrous nanostructures in a self-assembled manner. Their regularity and uniformity provide an important structural basis for subsequent surface modification and the dispersibility of composite materials. During the oxidative polymerization reaction of polyaniline, p-toluenesulfonic acid is introduced into the system as a dopant. Its main role is to convert polyaniline into a conductive state through a protonation mechanism. p-Toluenesulfonic acid is a strong acidic compound. Its sulfonic acid group binds to the amino and imino groups on the polyaniline molecular chain through electrostatic interaction, protonates these groups, and forms ion pairs. Protonated polyaniline exhibits high conductivity, and electrons can move freely on the molecular chain. In addition, the solubility and dispersibility of doped polyaniline are also significantly improved, making it easier to be uniformly mixed with other components during subsequent preparation processes.

[0007] The further functional modification of polyaniline nanofibers is completed through an ammonium orthomolybdate solution, aiming to endow polyaniline with higher chemical stability and electrochemical activity, while enhancing its dispersibility in composite materials. Under alkaline conditions, molybdate ions in the ammonium orthomolybdate solution bind to the protonated amino and imino groups on the polyaniline chain through electrostatic interaction to form stable ion pairs. The formation of this ion pair further increases the conductivity and surface activity of polyaniline. In addition, molybdate ions may also interact with the nitrogen atoms on the polyaniline molecular chain through hydrogen bonds, further enhancing the chemical stability of the polyaniline surface. This surface modification forms a functional protective layer centered on molybdenum on the polyaniline fibers. This protective layer not only improves the antioxidant ability of the material but also reduces its degradation rate in a corrosive environment, thereby enhancing the durability and environmental adaptability of polyaniline. The introduction of molybdate ions changes the charge distribution on the surface of polyaniline fibers, increasing the electrostatic repulsion force between the fibers, thus effectively preventing the aggregation of nanofibers. In addition, the binding of molybdate to polyaniline molecules provides more active sites on the fiber surface. These sites can interact with water molecules or other polar solvent molecules, thereby improving the dispersion stability of polyaniline in an aqueous phase system.

[0008] The modification of silica nanopowder is accomplished by γ-glycidoxypropyltrimethoxysilane (GPTMS). GPTMS is a functionalized silane, and its trimethoxysilyl group can undergo a hydrolysis condensation reaction with the hydroxyl groups on the silica surface to form siloxane bonds, while its epoxy group remains on the surface as an active site. By heating under reflux in absolute ethanol, the reaction between GPTMS and the silica surface proceeds sufficiently, thus achieving the surface functionalization of silica. The modified silica can not only bind better with polyaniline but also exhibits higher hydrophilicity and dispersibility, enabling it to be evenly distributed in the composite material and enhancing the mechanical properties of the material. The modified polyaniline nanofibers and the modified silica powder are mixed in deionized water, and this process realizes the composite of polyaniline and silica through electrostatic and intermolecular interactions. The conductive property of the modified polyaniline and the mechanical property of silica form a synergistic effect in the composite material, making the PANI-SiO2 composite material exhibit excellent corrosion resistance. Polyaniline can form a cathodic protection effect on the metal surface through its redox activity, while silica, as an inorganic filler, can provide a physical barrier effect in the coating to prevent the penetration of corrosive media. This multiple protection mechanism delays the occurrence of the corrosion process and improves the long-term protection ability of the coating.

[0009] During the nitrogen and sulfur co-doping process, graphene sheets are dispersed in an aqueous solution and mixed with thiourea and urea for a hydrothermal reaction. Graphene has a highly π-conjugated two-dimensional structure, and its chemical activity is mainly concentrated at the sheet edges and defect regions, which usually carry polar functional groups such as hydroxyl, carboxyl, or epoxy groups. However, the strong van der Waals forces between graphene sheets can cause them to easily aggregate in solution. Therefore, through the physical exfoliation effect induced by ultrasonic treatment, the sheets can be dispersed into single-layer or few-layer structures. Under hydrothermal reaction conditions, thiourea and urea decompose to produce various reactive intermediates. These intermediates can undergo chemical reactions with the active sites on the surface or edges of graphene to form nitrogen and sulfur doping structures. Nitrogen doping enhances the conductivity of graphene by introducing different types of nitrogen groups into the carbon skeleton of graphene, and at the same time enhances its antioxidant ability against oxidants in the corrosive medium. Sulfur doping endows it with higher hydrophilicity and chemical activity by introducing thiol, thioether, or sulfide structures on the surface of graphene. The presence of sulfur can also enhance the polarity and surface energy of graphene, promote its dispersion in the aqueous system, and further improve its chemical binding ability with the metal surface. Nitrogen and sulfur co-doping has a synergistic effect on the anti-corrosion performance. Nitrogen doping increases the electron cloud density of graphene, enabling it to act as an electron donor during the corrosion process and provide cathodic protection for the metal surface. Sulfur doping forms a passivation film on the surface of graphene by reacting with oxygen molecules or ions in the corrosive medium, thus preventing further penetration of the corrosive medium. This synergistic protection mechanism not only delays the corrosion behavior of the metal substrate but also provides a better interfacial chemical basis for subsequent modification.

[0010] In the phosphonate intercalation modification, nitrogen and sulfur co-doped graphene reacts with the intercalating agent in an organic solvent. The intercalating agent is an amphiphilic molecule, and its structural characteristics enable it to selectively bind to the surface of graphene. The phosphonate group can undergo strong interactions with the carboxyl or hydroxyl groups on the surface of graphene through chemical adsorption or bonding, thus achieving intercalation modification. The silyl group further introduces additional chemical bridging between the graphene sheets through hydrolysis and condensation reactions. This intercalation not only increases the spacing between graphene sheets but also reduces the van der Waals forces between the sheets, significantly enhancing the dispersion of graphene in solution. The contributions of intercalation modification to the anti-corrosion performance and interfacial bonding performance are mainly reflected in two aspects: Firstly, intercalation modification significantly reduces the penetration rate of the corrosive medium in the coating by constructing physical and chemical barriers between the graphene sheets. This barrier effect is one of the key mechanisms for graphene materials to play a role in anti-corrosion coatings. Secondly, the phosphonate group can form a strong chemical bond with the metal surface, thereby improving the adhesion of the coating to the metal substrate. This enhanced adhesion not only improves the mechanical properties of the coating but also significantly extends the service life of the coating.

[0011] The intercalated modified graphene and the silane coupling agent KH560 are refluxed in a water-ethanol mixed solution to complete the silane modification. The molecular structure of KH560 contains both trimethoxysilyl groups and epoxy groups. The trimethoxysilyl groups can hydrolyze to form silanols and undergo a condensation reaction with the hydroxyl or carboxyl groups on the graphene surface to form stable silicon-oxygen bonds, firmly fixing the KH560 molecules on the graphene surface while exposing their unreacted epoxy groups. The epoxy groups, as active sites, can undergo a crosslinking reaction with the resin matrix during the subsequent coating preparation process, thereby enhancing the interfacial bonding ability between the graphene and the coating matrix. The silane modification forms a protective functional coating on the graphene surface through chemical bonding, enhancing the chemical corrosion resistance of the graphene and further improving its stability in complex environments; secondly, the silane modification provides additional chemical active sites for the graphene, enabling it to achieve better compatibility and bonding with other coating components; the silane modification also significantly improves the dispersibility of the graphene, enabling it to be uniformly distributed in the coating system, forming a dense barrier structure while reducing the phenomenon of sheet agglomeration.

[0012] Using trifluoroethyl methacrylate as a monomer, under the initiation of azobisisobutyronitrile (AIBN), a fluorinated segment prepolymer is prepared through free radical polymerization. Trifluoroethyl methacrylate is a fluorinated monomer, and its molecular structure contains strongly polar fluorine atom bonds, which endow it with the characteristics of high hydrophobicity and low surface energy. During the polymerization process, AIBN decomposes to generate free radicals, and through the processes of chain initiation, chain growth, and chain termination, trifluoroethyl methacrylate is converted into a linear polymer with a certain molecular weight. Due to its high electronegativity and large volume, fluorine atoms can significantly reduce the free energy of the material surface, making the fluorinated segment prepolymer exhibit excellent hydrophobicity and anti-fouling properties. Hydrophobicity can effectively prevent the penetration of moisture and corrosive ions, forming the first barrier in the coating. Using N-vinylpyrrolidone (NVP), 3-(methacryloyloxy)propyltrimethoxysilane (MPTS), and maleic anhydride as comonomers, a multifunctional copolymer segment is prepared through free radical polymerization initiated by AIBN. NVP is a hydrophilic monomer, and its molecular structure contains a pyrrolidone ring. This polar structure can significantly improve the hydrophilicity and wettability of the copolymer. The introduction of NVP can improve the dispersibility of the material in the aqueous system, making it show stronger compatibility and stability in aqueous coatings. MPTS is a bifunctional silane monomer, and its molecule contains both a methacryloyloxy group that can participate in free radical polymerization and a trimethoxysilyl group. The trimethoxysilyl group can undergo hydrolysis and condensation reactions during the subsequent coating curing process, forming siloxane bonds with the hydroxyl groups or other active groups on the substrate surface. This chemical bonding significantly enhances the adhesion between the coating and the substrate, thereby improving the mechanical properties and durability of the coating. The introduction of maleic anhydride further increases the functional group density of the copolymer. Its anhydride group can undergo chemical reactions with the metal surface or other coating components to form stable chemical bonds, enhancing the interfacial bonding ability of the copolymer. At the same time, its polar anhydride structure also improves the corrosion resistance of the coating.

[0013] The fluorine-containing segment prepolymer, the multifunctional copolymer segment and pentaerythritol tetra(3-mercaptopropionate) (PETMP) are mixed, and a macromolecular structure is prepared through thiol-ene click chemical reaction. Under high-temperature conditions, the thiol groups homolytically generate sulfur radicals, which undergo an addition reaction with the double bonds on the olefin bonds, thereby forming stable C-S bonds. PETMP is a multi-functional thiol compound, and its molecular structure contains four thiol groups, which enables it to undergo a cross-linking reaction with the double bond sites in the fluorine-containing segment and the multifunctional copolymer segment to form a highly cross-linked macromolecular structure. This cross-linking reaction not only increases the molecular weight and mechanical strength of the material, but also endows it with higher chemical stability and weather resistance. The introduction of the fluorine-containing segment prepolymer makes the macromolecular material have hydrophobic and low surface energy characteristics at one end of the molecular chain, while the multifunctional copolymer segment improves the interfacial binding ability and dispersibility of the material through the combination of hydrophilic and reactive functional groups. The two-segment macromolecular structure achieves the balance of hydrophobicity and hydrophilicity, enabling the material to exhibit excellent hydrophobic and anti-corrosion properties in the coating system and being compatible with other coating components. The preparation of the functionalized emulsion is completed by mixing the macromolecular solution with emulsifier Tween 80 and dispersing it into deionized water. The fluorine-containing segment in the functionalized emulsion provides low surface energy and hydrophobicity, which can reduce the adhesion and penetration of corrosive media; the multifunctional copolymer segment enhances the interfacial binding force between the coating and the substrate through the chemical reaction of maleic anhydride and silyl groups; the thiol-ene cross-linked structure improves the mechanical properties and durability of the coating by enhancing the cross-linking density between molecules.

[0014] The main function of the PANI-SiO2 composite material is to provide redox and physical barriers. Modified polyaniline (PANI) forms a cathodic protection effect on the metal surface through its conductivity and redox activity. When corrosive media penetrate into the coating, PANI can generate a protective oxide film on the metal surface through redox cycling, reducing the occurrence of metal oxidation reactions. The introduction of ammonium paramolybdate further enhances this effect. Molybdate ions combine with the metal surface to form a passivation film to reduce the corrosion rate. SiO2 nanoparticles block the diffusion path of corrosive media through an inorganic barrier effect. Their high dispersibility and surface activity enable them to be evenly distributed in the coating matrix, thereby improving the density and impermeability of the coating. The composite structure between PANI and SiO2 also increases the mechanical strength and durability of the coating. The two-dimensional sheet structure of graphene in the silane-modified graphene powder has an extremely high specific surface area and excellent barrier ability, forming a dense physical barrier in the coating. Nitrogen and sulfur co-doping further enhances the conductivity and chemical activity of graphene, enabling it to assist the redox barrier effect of PANI-SiO2 and enhancing the cathodic protection of the metal surface. In addition, the silane modification introduces silicon-containing groups and epoxy groups, enabling graphene to chemically crosslink with the epoxy resin matrix, thereby enhancing the adhesion and interfacial stability of the coating. The modification of the silane coupling agent also improves the dispersibility of graphene in the aqueous system, ensuring its uniform distribution in the coating.

[0015] The functionalized emulsion provides hydrophobicity, anti-corrosion barrier, and enhanced interfacial bonding functions through molecular design. The fluorine-containing segment in the emulsion endows the coating with low surface energy and excellent hydrophobicity, effectively preventing the adsorption and penetration of moisture and corrosive ions. The multifunctional copolymer segment improves the dispersibility of the emulsion in the aqueous system through the hydrophilicity of N-vinylpyrrolidone (NVP), and at the same time chemically crosslinks with the coating matrix through silane groups and maleic anhydride structures, enhancing the interfacial bonding force and improving the mechanical properties of the coating. The wettability regulation ability of the emulsion improves the spreading property of the coating on the substrate surface, ensuring a uniform coating effect and thus reducing coating defects. The performance of the coating is enhanced through multiple synergistic effects among the three materials. The two-dimensional barrier of the silane-modified graphene and the inorganic barrier effect of PANI-SiO2 complement each other, forming a multi-layer anti-corrosion barrier structure. The conductive polyaniline in PANI-SiO2 combines with the conductivity of the silane-modified graphene, further enhancing the cathodic protection effect of the coating. The fluorine-containing hydrophobic segment of the functionalized emulsion synergizes with the barrier effect of the silane-modified graphene to form a dual protection structure of a hydrophobic surface and an internal barrier, effectively reducing the adsorption of corrosive media. The silane groups in the emulsion also chemically crosslink with the SiO2 particles in PANI-SiO2 and the surface active groups of the silane-modified graphene, enhancing the overall structural stability and interfacial bonding force of the coating.

[0016] As a preferred technical solution of the present invention, in S1, the mass ratio of aniline, p-toluenesulfonic acid and ammonium persulfate solution is 20:5:125.

[0017] In some alternative embodiments, the mass fraction of the ammonium persulfate solution is 20 wt.%.

[0018] In some alternative embodiments, the time for maintaining stirring is 10 - 12 h, for example, it can be 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h or 12 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] In some alternative embodiments, the mass fraction of the ammonium paramolybdate solution is 5 wt.%, and the pH of the solution is 8.

[0020] In some alternative embodiments, the mass-to-volume ratio of the SiO2 nanoflour, GPTMS and absolute ethanol is 10 g:5 mL:50 mL.

[0021] In some alternative embodiments, the first temperature is 80 - 90 °C, for example, it can be 80 °C, 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, 89 °C or 90 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] In some alternative embodiments, the time for stirring and refluxing is 2 - 3 h, for example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] In some alternative embodiments, the mass ratio of the modified polyaniline nanofibers to the modified SiO2 is 2:1.

[0024] In some alternative embodiments, the second temperature is 50 - 60 °C, for example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In some alternative embodiments, the time of the stirring reaction is 5 - 6 h. For example, it can be 5 h, 5.1 h, 5.2 h, 5.3 h, 5.4 h, 5.5 h, 5.6 h, 5.7 h, 5.8 h, 5.9 h or 6 h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0026] As a preferred technical solution of the present invention, in S2, the mass ratio of the graphene, thiourea and urea is 10:10:8.

[0027] In some alternative embodiments, the third temperature is 180 - 190 °C. For example, it can be 180 °C, 181 °C, 182 °C, 183 °C, 184 °C, 185 °C, 186 °C, 187 °C, 188 °C, 189 °C or 190 °C. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0028] In some alternative embodiments, the reaction time at the third temperature is 12 - 13 h. For example, it can be 12 h, 12.1 h, 12.2 h, 12.3 h, 12.4 h, 12.5 h, 12.6 h, 12.7 h, 12.8 h, 12.9 h or 13 h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0029] In some alternative embodiments, the mass - volume ratio of the N,S - co - doped graphene powder, the intercalating agent and N - methylpyrrolidone is 8 g:5 g:100 mL.

[0030] In some alternative embodiments, the intercalating agent is Dynasylan® 1189.

[0031] In some alternative embodiments, the fourth temperature is 70 - 80 °C. For example, it can be 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, 76 °C, 77 °C, 78 °C, 79 °C or 80 °C. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0032] In some alternative embodiments, the stirring time at the fourth temperature is 8 - 9 h. For example, it can be 8 h, 8.1 h, 8.2 h, 8.3 h, 8.4 h, 8.5 h, 8.6 h, 8.7 h, 8.8 h, 8.9 h or 9 h. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0033] In some alternative embodiments, the mass - volume ratio of the partially intercalated graphene material and KH560 is 8 g:3 mL.

[0034] In some alternative embodiments, the reflux reaction time is 2 - 3 h. For example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, or 3 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] As a preferred technical solution of the present invention, in S3, the mass ratio of trifluoroethyl methacrylate to azobisisobutyronitrile is 15:0.5.

[0036] In some alternative embodiments, the reaction time at the second temperature is 4 - 5 h. For example, it can be 4 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h, or 5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In some alternative embodiments, the mass ratio of N - vinylpyrrolidone, 3 - (methacryloyloxy)propyltrimethoxysilane, maleic anhydride, and azobisisobutyronitrile is 10 g:10 g:10 g:1 g.

[0038] In some alternative embodiments, the stirring reaction time at the second temperature is 4 - 5 h. For example, it can be 4 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h, or 5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0039] In some alternative embodiments, the mass ratio of the fluorine - containing segment prepolymer, the multifunctional copolymer segment, and pentaerythritol tetrakis(3 - mercaptopropionate) is 2:2:1.

[0040] In some alternative embodiments, the stirring reaction time at the fourth temperature is 10 - 12 h. For example, it can be 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h, or 12 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] In some alternative embodiments, the mass - to - volume ratio of the macromolecular solution to Tween 80 is 70 mL:1 g.

[0042] In some alternative embodiments, the heat preservation time is 1 - 2 h, for example, it can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] As a preferred technical solution of the present invention, in S4, the mass ratio of the leveling agent, defoaming agent, thickening agent, waterborne epoxy resin, silane-modified graphene powder, functionalized emulsion to PANI-SiO₂ is 0.5:0.5:2:200:3:15:5.

[0044] In a second aspect, the present invention provides a graphene-modified waterborne anti-corrosion coating for marine steel structures prepared by the preparation method described in the first aspect.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The conductive property of the modified polyaniline and the mechanical property of the silica form a synergistic effect in the composite material, making the PANI-SiO₂ composite material exhibit excellent anti-corrosion performance. Polyaniline can form a cathodic protection effect on the metal surface through its redox activity. At the same time, silica, as an inorganic filler, can provide a physical barrier effect in the coating to prevent the penetration of corrosive media; (2) The two-dimensional sheet structure of graphene has an extremely high specific surface area and excellent barrier performance. The graphene sheets can extend the diffusion path of the corrosive media, reducing the possibility of moisture, oxygen, and corrosive ions penetrating to the metal interface. The doping of nitrogen increases the electron cloud density of graphene, providing cathodic protection for the metal surface, and the doping of sulfur forms a passivation film on the graphene surface by reacting with oxygen molecules or ions in the corrosive media. The silane modification introduces siloxane bonds and epoxy groups on the graphene surface, enabling it to undergo a chemical cross-linking reaction with the coating matrix. The chemical bonding of the siloxane bonds enhances the interfacial stability of the coating, and the epoxy groups can further react with the epoxy resin matrix to improve the adhesion of the coating; (3) The introduction of the fluorine-containing prepolymer in the functionalized emulsion reduces the surface free energy of the coating, making the coating exhibit excellent hydrophobicity and anti-fouling properties. The multifunctional copolymer segment undergoes a chemical cross-linking reaction with the substrate through silane groups and maleic anhydride structures, enhancing the adhesion of the coating, and the thiol-ene cross-linking structure improves the mechanical properties and durability of the coating by enhancing the intermolecular cross-linking density. Description of the Drawings

[0046] Figure 1 It is a flowchart of the preparation method of the graphene-modified waterborne anti-corrosion coating for marine steel structures provided by Embodiments 1 - 4 of the present invention. Detailed Embodiments

[0047] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0048] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products without any further purification treatment.

[0049] Example 1

[0050] As Figure 1 shown, this example provides a preparation method of a waterborne anti-corrosion coating for marine steel structures modified by graphene. The preparation method specifically includes the following steps: S1, In an ice-water bath, disperse 20 g of aniline, 5 g of p-toluenesulfonic acid, and 125 g of a 20 wt.% ammonium persulfate solution in 200 mL of deionized water, keep stirring for 10.6 h, wash and filter to obtain polyaniline nanofibers, and then immerse the polyaniline nanofibers in a 5 wt.% ammonium orthomolybdate solution, stir well, centrifuge, wash and dry to obtain modified polyaniline nanofibers. Disperse 10 g of SiO2 nanopowder and 5 mL of GPTMS in 50 mL of absolute ethanol, adjust the temperature to 88 °C, stir and reflux for 2.0 h, filter, wash, and vacuum dry to obtain modified SiO2. Disperse 20 g of modified polyaniline nanofibers and 10 g of modified SiO2 in 100 mL of deionized water, adjust the temperature to 54 °C and adjust the pH to 7, stir and react for 5.3 h, then centrifuge, wash, and freeze-dry to obtain PANI-SiO2; S2, Disperse 10 g of graphene, 10 g of thiourea, and 8 g of urea in 100 mL of deionized water, ultrasonically disperse, transfer to a reaction kettle, and adjust the temperature to 188 °C for reaction for 12.4 h. After the reaction, wash the product with a 1 wt.% KOH solution and dry to obtain N,S co-doped graphene powder. Disperse 8 g of N,S co-doped graphene powder and 5 g of an intercalating agent in 100 mL of N-methylpyrrolidone, adjust the temperature to 74 °C, stir for 8.2 h, filter, wash, and dry to obtain a partially intercalated graphene material. Disperse 8 g of the partially intercalated graphene material and 3 mL of KH560 in 50 mL of an ethanol-water solution, adjust the pH to 5 and adjust the temperature to 55 °C, reflux and react for 2.2 h, centrifuge, wash, and dry to obtain silane-modified graphene powder; S3, 15g of trifluoroethyl methacrylate and 0.5g of azobisisobutyronitrile were dispersed in 50mL of dimethyl sulfoxide, the temperature was adjusted to 50°C in a nitrogen atmosphere to react for 4.0h, and ethanol was added after the reaction to separate and obtain a fluorinated segment prepolymer, 5g of N-vinyl pyrrolidone, 5g of 3-methacryloxypropyltrimethoxysilane, 5g of maleic anhydride and 0.5g of azobisisobutyronitrile were dispersed in 50mL of dimethyl sulfoxide, the temperature was adjusted to 55°C in a nitrogen atmosphere to react for 4.2h with stirring, and ethanol was added after the reaction to separate and obtain a multifunctional copolymer segment, 10g of the fluorinated segment prepolymer, 10g of the multifunctional copolymer segment and 5g of pentaerythritol tetrakis(3-mercaptopropionic acid) were dispersed in 30mL of dimethyl sulfoxide, the temperature was adjusted to 77°C to react with stirring for 11.8h to obtain a macromolecular solution, and 70mL of the macromolecular solution was mixed with 1g of Tween 80 was dispersed into 200 mL of deionized water and stirred, the pH was adjusted to 8 and the temperature was adjusted to 70 °C for 1.6 h to obtain a functionalized emulsion; S4, add 0.5g of leveling agent, 0.5g of defoaming agent and 2g of thickener to 200g of water-based epoxy resin in sequence and mix evenly, then add 3g of silane-modified graphene powder, 15g of functionalized emulsion and 5g of PANI-SiO2 to the water-based epoxy resin in sequence, mix evenly and add curing agent when using to obtain a water-based anti-corrosion coating for marine steel structures based on graphene modification.

[0051] Example 2

[0052] This embodiment provides a method for preparing a water-based anti-corrosion coating for marine steel structures based on graphene modification, and the preparation method specifically comprises the following steps: S1, ice water bath, disperse 20g aniline, 5g p-toluenesulfonic acid and 125g, 20wt.% ammonium persulfate solution in 200mL deionized water and keep stirring for 10.0h, wash and filter to obtain polyaniline nanofibers, then immerse the polyaniline nanofibers in 5wt.% ammonium orthomolybdate solution, stir thoroughly, centrifuge, wash and dry to obtain modified polyaniline nanofibers. Disperse 10g SiO2 nanopowder and 5mL GPTMS in 50mL anhydrous ethanol, adjust to 80℃, stir and reflux for 2.6h, filter, wash and vacuum dry to obtain modified SiO2, disperse 20g modified polyaniline nanofibers and 10g modified SiO2 in 100mL deionized water, adjust the temperature to 50℃ and adjust the pH to 7, stir and react for 5.0h, centrifuge and wash, freeze-dry to obtain PANI-SiO2; S2. Disperse 10 g of graphene, 10 g of thiourea, and 8 g of urea in 100 mL of deionized water. After ultrasonic dispersion, transfer it to a reaction kettle, adjust the temperature to 180 °C, and react for 12.0 h. After the reaction, wash the product with 1 wt.% KOH solution and dry it to obtain N,S co-doped graphene powder. Disperse 8 g of N,S co-doped graphene powder and 5 g of intercalating agent in 100 mL of N-methylpyrrolidone, adjust the temperature to 70 °C, and stir for 8.4 h. Filter, wash, and dry to obtain partially intercalated graphene material. Disperse 8 g of partially intercalated graphene material and 3 mL of KH560 in 50 mL of ethanol aqueous solution, adjust the pH to 5, and adjust the temperature to 51 °C, and reflux for 2.8 h. After centrifugation, washing, and drying, obtain silane-modified graphene powder; S3. Disperse 15 g of trifluoroethyl methacrylate and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, adjust the temperature to 57 °C and react for 4.8 h. After the reaction, add ethanol for separation to obtain a fluorine-containing segment prepolymer. Disperse 5 g of N-vinylpyrrolidone, 5 g of 3-methacryloxypropyltrimethoxysilane, 5 g of maleic anhydride, and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, adjust the temperature to 50 °C and stir and react for 4.0 h. After the reaction, add ethanol for separation to obtain a multifunctional copolymer segment. Disperse 10 g of fluorine-containing segment prepolymer, 10 g of multifunctional copolymer segment, and 5 g of pentaerythritol tetra(3-mercaptopropionate) in 30 mL of dimethyl sulfoxide, adjust the temperature to 70 °C, and stir and react for 10.0 h to obtain a macromolecular solution. Then disperse 70 mL of the macromolecular solution and 1 g of Tween 80 in 200 mL of deionized water and stir, adjust the pH to 8, and adjust the temperature to 70 °C for heat preservation for 1.0 h to obtain a functionalized emulsion; S4. Add 0.5 g of leveling agent, 0.5 g of defoaming agent, and 2 g of thickener to 200 g of waterborne epoxy resin in sequence and mix evenly. Then add 3 g of silane-modified graphene powder, 15 g of functionalized emulsion, and 5 g of PANI-SiO2 to the waterborne epoxy resin in sequence. After mixing evenly, add a curing agent during use to obtain a graphene-modified waterborne anticorrosive coating for marine steel structures.

[0053] Example 3

[0054] This example provides a preparation method of a graphene-modified waterborne anticorrosive coating for marine steel structures. The preparation method specifically includes the following steps: S1, Ice bath: Disperse 20 g of aniline, 5 g of p-toluenesulfonic acid, and 125 g of 20 wt.% ammonium persulfate solution in 200 mL of deionized water, stir for 11.4 h, wash and filter to obtain polyaniline nanofibers. Then immerse the polyaniline nanofibers in 5 wt.% ammonium orthomolybdate solution, stir thoroughly, centrifuge, wash, and dry to obtain modified polyaniline nanofibers. Disperse 10 g of SiO2 nanopowder and 5 mL of GPTMS in 50 mL of absolute ethanol, adjust the temperature to 84 °C, stir and reflux for 3.0 h, filter, wash, and vacuum dry to obtain modified SiO2. Disperse 20 g of modified polyaniline nanofibers and 10 g of modified SiO2 in 100 mL of deionized water, adjust the temperature to 60 °C and the pH to 7, stir and react for 5.7 h, then centrifuge, wash, and freeze-dry to obtain PANI-SiO2; S2: Disperse 10 g of graphene, 10 g of thiourea, and 8 g of urea in 100 mL of deionized water, ultrasonically disperse, transfer to a reaction kettle, adjust the temperature to 190 °C, and react for 12.7 h. After the reaction, wash the product with 1 wt.% KOH solution and dry to obtain N,S co-doped graphene powder. Disperse 8 g of N,S co-doped graphene powder and 5 g of an intercalating agent in 100 mL of N-methylpyrrolidone, adjust the temperature to 71 °C, stir for 9.0 h, filter, wash, and dry to obtain a partially intercalated graphene material. Disperse 8 g of the partially intercalated graphene material and 3 mL of KH560 in 50 mL of an ethanol aqueous solution, adjust the pH to 5 and the temperature to 50 °C, reflux and react for 2.0 h, centrifuge, wash, and dry to obtain silane-modified graphene powder; S3: Disperse 15 g of trifluoroethyl methacrylate and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide, adjust the temperature to 53 °C under a nitrogen atmosphere and react for 5.0 h. After the reaction, add ethanol for separation to obtain a fluorinated segment prepolymer. Disperse 5 g of N-vinylpyrrolidone, 5 g of 3-methacryloxypropyltrimethoxysilane, 5 g of maleic anhydride, and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide, adjust the temperature to 60 °C under a nitrogen atmosphere and stir and react for 4.7 h. After the reaction, add ethanol for separation to obtain a multifunctional copolymer segment. Disperse 10 g of the fluorinated segment prepolymer, 10 g of the multifunctional copolymer segment, and 5 g of pentaerythritol tetrakis(3-mercaptopropionate) in 30 mL of dimethyl sulfoxide, adjust the temperature to 74 °C, stir and react for 12.0 h to obtain a macromolecular solution. Then disperse 70 mL of the macromolecular solution and 1 g of Tween 80 in 200 mL of deionized water, stir, adjust the pH to 8 and the temperature to 70 °C, and keep warm for 1.4 h to obtain a functionalized emulsion; S4. Add 0.5 g of leveling agent, 0.5 g of defoamer, and 2 g of thickener to 200 g of waterborne epoxy resin in sequence and mix evenly. Then add 3 g of silane-modified graphene powder, 15 g of functionalized emulsion, and 5 g of PANI-SiO2 to the waterborne epoxy resin in sequence. After mixing evenly, add a curing agent during use to obtain a waterborne anticorrosive coating for marine steel structures based on graphene modification.

[0055] Example 4

[0056] This example provides a preparation method for a waterborne anticorrosive coating for marine steel structures based on graphene modification. The preparation method specifically includes the following steps: S1. In an ice-water bath, disperse 20 g of aniline, 5 g of p-toluenesulfonic acid, and 125 g of 20 wt.% ammonium persulfate solution in 200 mL of deionized water and keep stirring for 12.0 h. Wash and filter to obtain polyaniline nanofibers. Then immerse the polyaniline nanofibers in a 5 wt.% ammonium paramolybdate solution, stir well, and then centrifuge, wash, and dry to obtain modified polyaniline nanofibers. Disperse 10 g of SiO2 nanoflour and 5 mL of GPTMS in 50 mL of absolute ethanol, adjust the temperature to 90 °C, stir and reflux for 2.4 h, filter, wash, and vacuum dry to obtain modified SiO2. Disperse 20 g of modified polyaniline nanofibers and 10 g of modified SiO2 in 100 mL of deionized water, adjust the temperature to 57 °C and adjust the pH to 7, stir and react for 6.0 h, then centrifuge, wash, and freeze-dry to obtain PANI-SiO2; S2. Disperse 10 g of graphene, 10 g of thiourea, and 8 g of urea in 100 mL of deionized water. After ultrasonic dispersion, transfer it to a reaction kettle and adjust the temperature to 186 °C and react for 13.0 h. After the reaction, wash the product with 1 wt.% KOH solution and dry to obtain N,S co-doped graphene powder. Disperse 8 g of N,S co-doped graphene powder and 5 g of intercalating agent in 100 mL of N-methylpyrrolidone, adjust the temperature to 80 °C and stir for 8.0 h, filter, wash, and dry to obtain a partially intercalated graphene material. Disperse 8 g of the partially intercalated graphene material and 3 mL of KH560 in 50 mL of ethanol aqueous solution, adjust the pH to 5 and adjust the temperature to 60 °C, reflux and react for 3.0 h, centrifuge, wash, and dry to obtain silane-modified graphene powder; S3. Disperse 15 g of trifluoroethyl methacrylate and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, adjust the temperature to 60 °C and react for 4.6 h. After the reaction, add ethanol for separation to obtain a fluorinated segment prepolymer. Disperse 5 g of N-vinylpyrrolidone, 5 g of 3-methacryloxypropyltrimethoxysilane, 5 g of maleic anhydride and 0.5 g of azobisisobutyronitrile in 50 mL of dimethyl sulfoxide. Under a nitrogen atmosphere, adjust the temperature to 58 °C and stir and react for 5.0 h. After the reaction, add ethanol for separation to obtain a multifunctional copolymer segment. Disperse 10 g of the fluorinated segment prepolymer, 10 g of the multifunctional copolymer segment and 5 g of pentaerythritol tetrakis(3-mercaptopropionate) in 30 mL of dimethyl sulfoxide, adjust the temperature to 80 °C and stir and react for 10.6 h to obtain a macromolecular solution. Then disperse 70 mL of the macromolecular solution and 1 g of Tween 80 into 200 mL of deionized water and stir, adjust the pH to 8 and adjust the temperature to 70 °C and keep warm for 2.0 h to obtain a functionalized emulsion; S4. Add 0.5 g of a leveling agent, 0.5 g of an antifoaming agent, and 2 g of a thickener to 200 g of waterborne epoxy resin in sequence and mix evenly. Then add 3 g of silane-modified graphene powder, 15 g of the functionalized emulsion and 5 g of PANI-SiO2 to the waterborne epoxy resin in sequence. After mixing evenly, add a curing agent during use to obtain a waterborne anti-corrosion coating for marine steel structures based on graphene modification.

[0057] Comparative Example 1 This comparative example provides a preparation method of a waterborne anti-corrosion coating for marine steel structures based on graphene modification. The difference from Example 1 is that the mass of thiourea in S2 is 20 g, which is 10 g more than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0058] Comparative Example 2 This comparative example provides a preparation method of a waterborne anti-corrosion coating for marine steel structures based on graphene modification. The difference from Example 1 is that the mass of thiourea in S2 is 1 g, which is 9 g less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0059] Comparative Example 3 This comparative example provides a preparation method of a waterborne anti-corrosion coating for marine steel structures based on graphene modification. The difference from Example 1 is that the mass of pentaerythritol tetrakis(3-mercaptopropionate) in S3 is 10 g, which is 5 g more than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0060] Comparative Example 4 This comparative example provides a preparation method of a waterborne anti-corrosion coating for marine steel structures modified with graphene. The difference from Example 1 is that the mass of pentaerythritol tetra(3-mercaptopropionate) in S3 is 1 g, which is 4 g less than that in Example 1. Other process parameters and operating conditions are exactly the same as those in Example 1.

[0061] The adhesion test standard is GB / T 9286-2021; the salt spray resistance test standard is GB / T 31588.1-2015; the impact resistance test standard is GB / T 1732-2020. The test results are shown in Table 1.

[0062] Table 1 Test results of waterborne anti-corrosion coatings for marine steel structures modified with graphene in Examples 1-4 and Comparative Examples 1-4

[0063] As can be seen from Table 1, compared with Example 1, the adhesion, salt spray resistance and impact resistance of Comparative Example 1 are all reduced; the adhesion, salt spray resistance and impact resistance of Comparative Example 2 are all reduced. This is because too much thiourea in Comparative Example 1 may lead to excessive doping of sulfur and nitrogen in the graphene sheets, resulting in too many structural defects, a decrease in the integrity and mechanical strength of the graphene sheets, a weakening of the physical barrier effect of the coating, and a decrease in the interfacial bonding ability between graphene and the matrix material (such as waterborne epoxy resin and PANI-SiO2). Too many defects will increase the penetration path of corrosive media through the coating, resulting in a decrease in salt spray resistance. In Comparative Example 2, the amount of thiourea is too small, so the doping amount of sulfur and nitrogen in graphene is insufficient, which cannot significantly improve the chemical activity and wettability of the graphene surface, resulting in difficulty in forming a strong interfacial bond between graphene and the coating matrix. Insufficient doping may reduce the electrochemical activity of graphene and weaken its synergistic cathodic protection effect with PANI-SiO2, affecting the salt spray resistance.

[0064] As can be seen from Table 1, compared with Example 1, the adhesion, salt spray resistance and impact resistance of Comparative Example 3 are all reduced; the adhesion, salt spray resistance and impact resistance of Comparative Example 4 are all reduced. This is because in Comparative Example 3, too much pentaerythritol tetra(3-mercaptopropionate) will lead to too high a crosslinking density of the functionalized emulsion, a decrease in the flexibility of the coating, and thus a decrease in its impact resistance. Excessive crosslinking may lead to an increase in the internal stress of the coating, and peeling or cracking may occur at the interface between the coating and the substrate, resulting in a decrease in adhesion. A high crosslinking density may lead to the formation of microcracks on the coating surface, reducing the salt spray resistance. In Comparative Example 4, the amount of pentaerythritol tetra(3-mercaptopropionate) is insufficient, and the crosslinking network in the functionalized emulsion cannot be fully formed, resulting in a decrease in the chemical bonding force and impact resistance between the coating and the substrate. The hydrophobicity and compactness of the coating mainly depend on the integrity of the crosslinking network. Insufficient crosslinking will lead to a decrease in the barrier performance of the coating, making it easier for corrosive media to penetrate to the surface of the metal substrate.

[0065] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. Preparation method of waterborne anticorrosive coating for marine steel structure based on graphene modification, characterized in that The preparation method includes: S1. Stir aniline, p-toluenesulfonic acid and ammonium persulfate solution to obtain polyaniline nanofibers, then immerse the polyaniline nanofibers in ammonium orthomolybdate solution to obtain modified polyaniline nanofibers. React SiO2 nanopowder with GPTMS to obtain modified SiO2, and react the modified polyaniline nanofibers with the modified SiO2 to obtain PANI-SiO2; S2. React graphene, thiourea and urea to obtain N,S co-doped graphene powder. React the N,S co-doped graphene powder with an intercalating agent to obtain a partially intercalated graphene material, and react the partially intercalated graphene material with KH560 to obtain a silane-modified graphene powder; S3. React trifluoroethyl methacrylate with azobisisobutyronitrile to obtain a fluorine-containing segment prepolymer. React N-vinylpyrrolidone, 3-(methacryloyloxy)propyltrimethoxysilane, maleic anhydride and azobisisobutyronitrile to obtain a multifunctional copolymer segment. React the fluorine-containing segment prepolymer, the multifunctional copolymer segment with pentaerythritol tetra(3-mercaptopropionate) to obtain a macromolecular solution, and then mix and stir the macromolecular solution with Tween 80 to obtain a functionalized emulsion; S4. Add a leveling agent, an antifoaming agent and a thickening agent to waterborne epoxy resin, and then add the silane-modified graphene powder, the functionalized emulsion and PANI-SiO2 to the waterborne epoxy resin to obtain a waterborne anticorrosive coating for marine steel structures modified with graphene.

2. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, characterized in that In S1: The mass ratio of the aniline, p-toluenesulfonic acid and ammonium persulfate solution is 20:5:125; The mass-volume ratio of the SiO2 nanopowder to GPTMS is 10g:5mL.

3. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S1: The mass ratio of the modified polyaniline nanofibers to the modified SiO2 is 2:

1.

4. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S2: The mass ratio of the graphene, thiourea and urea is 10:10:8; The mass ratio of the N,S co-doped graphene powder to the intercalating agent is 8:

5.

5. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, characterized in that, In S2: The mass-volume ratio of the partially intercalated graphene material to KH560 is 8g:3mL.

6. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S3: The mass ratio of the trifluoroethyl methacrylate to azobisisobutyronitrile is 15:0.

5.

7. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S3: The mass ratio of the N-vinylpyrrolidone, 3-(methacryloyloxy)propyltrimethoxysilane, maleic anhydride, azobisisobutyronitrile is 10g:10g:10g:1g.

8. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S3: The mass ratio of the fluorine-containing segment prepolymer, the multifunctional copolymer segment and pentaerythritol tetra(3-mercaptopropionate) is 2:2:1; The mass-volume ratio of the macromolecular solution to Tween 80 is 70mL:1g.

9. The preparation method of the waterborne anti-corrosion coating for marine steel structures based on graphene modification according to claim 1, wherein, In S4: The mass ratio of the leveling agent, the antifoaming agent, the thickening agent, the waterborne epoxy resin, the silane-modified graphene powder, the functionalized emulsion and PANI-SiO2 is 0.5:0.5:2:200:3:15:

5.

10. Waterborne anti-corrosion coating for marine steel structures modified by graphene, characterized in that, Prepared by the preparation method according to any one of claims 1-9.

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