Graphene anticorrosive coating and method for preparing the same

Abstract

This invention provides a graphene anti-corrosion coating, comprising the following raw materials in parts by weight: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts water-based acrylic emulsion, 30-40 parts water-based epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide / disinfectant, and 0.3-0.8 parts adhesion promoter. The graphene anti-corrosion coating provided by this invention solves the problem of graphene's high surface energy causing easy agglomeration and difficulty in dispersion in coatings by chemically modifying graphene powder with silane coupling agent KH560 under anhydrous conditions. It uses water-based acrylic emulsion and water-based epoxy resin emulsion as the main film-forming substances and deionized water as the dispersion medium, replacing the organic solvents in traditional graphene anti-corrosion coatings. The coating formulation has extremely low VOC content, making it environmentally friendly and harmless to the health of construction workers.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection technology, and in particular to a graphene anti-corrosion coating and its preparation method. Background Technology

[0002] When metallic materials come into contact with the surrounding medium during use, they are damaged and deteriorate due to chemical and electrochemical reactions, a process known as metal corrosion. Commonly used metal corrosion protection technologies include cathodic protection, anodic protection, corrosion inhibitors, and organic / polymer coating protection. Among these, coating protection is the simplest and most suitable method. As a basic component of organic coatings, epoxy resin coatings possess excellent barrier properties, chemical inertness, electrical insulation properties, and strong adhesion to metal surfaces, making them particularly suitable as film-forming substances for anti-corrosion coatings. Traditional water-based epoxy resin coatings are widely used due to their low cost and environmental friendliness.

[0003] Waterborne epoxy resins, after curing, have a high cross-linking density, which easily leads to coating cracking and the formation of microcracks. Once the coating is damaged, it easily peels off, leaving the metal unprotected and susceptible to corrosion. Graphene, currently the thinnest two-dimensional material, possesses excellent electrical and thermal conductivity, a large specific surface area, high mechanical strength, and stable chemical properties. It is widely used as a filler to increase the propagation path of corrosive media, thereby improving the corrosion resistance of the coating.

[0004] However, in practical applications, the research on graphene coatings is quite complex and incomplete. Due to its conjugated structure, graphene is prone to agglomeration and poor dispersibility in solvents, which affects its performance. Furthermore, its high conductivity can actually accelerate corrosion. Summary of the Invention

[0005] This invention provides a graphene anti-corrosion coating and its preparation method to solve the problems mentioned in the background art.

[0006] This invention provides a graphene anti-corrosion coating, comprising the following raw materials in parts by weight: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts waterborne acrylic emulsion, 30-40 parts waterborne epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter.

[0007] Optionally, the preparation process of modified graphene is as follows: 6 parts by weight of graphene powder, 0.6-1.2 parts by weight of silane coupling agent and 0.02-0.05 parts by weight of catalyst are dispersed in anhydrous organic solvent, heated to 100-110℃ under nitrogen protection, and 0.05-0.15 parts by weight of water are slowly added while stirring. The reaction is carried out at a constant temperature for 2-4 hours. After the reaction, the graphene is washed and dried to obtain modified graphene.

[0008] Optionally, the graphene powder raw material used in the modified graphene has an average sheet diameter of 1-3 μm and a thickness of 1-5 nm.

[0009] Optionally, the silane coupling agent is KH560, the catalyst is dibutyltin dilaurate, and the anhydrous organic solvent is toluene.

[0010] Optionally, the washing process involves washing the product three times with anhydrous ethanol, and the drying process involves vacuum drying at 60°C for 8 hours.

[0011] Optionally, the waterborne acrylic emulsion has a solid content of 45%, and the waterborne epoxy resin emulsion has an epoxy equivalent of 450-550 g / eq and a solid content of 50%.

[0012] Optionally, the anti-rust pigment is a mixture of zinc phosphate and aluminum tripolyphosphate, wherein the mass ratio of zinc phosphate to aluminum tripolyphosphate is 1:(0.5-1).

[0013] Optionally, the film-forming aid is dodecyl alcohol ester, the leveling agent is polydimethylsiloxane, the bactericide is isothiazolinone, and the adhesion promoter is epoxy phosphate ester.

[0014] The present invention also provides a method for preparing the above-mentioned graphene anti-corrosion coating, comprising the following steps: (1) Weigh the following raw materials according to the following weight proportions: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts water-based acrylic emulsion, 30-40 parts water-based epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter; (2) Add the modified graphene powder weighed in step (1) to 20-30 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 200-400 r / min for 10-20 min, and then disperse ultrasonically at 500-800 W and 20-40 kHz for 1-2 h to obtain modified graphene aqueous dispersion; (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with a pH adjuster, then stir at 200-400 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 20-40 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 500-700 r / min for 20-40 minutes, then increase the speed to 700-1000 r / min, slowly add the A material obtained in step (3), and continue to disperse for 30-60 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 12-48 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0015] Optionally, the pH adjuster in step (3) is 2-amino-2-methyl-1-propanol.

[0016] The beneficial effects of the graphene anti-corrosion coating and its preparation method provided by this invention are as follows: 1. By chemically modifying graphene powder with silane coupling agent KH560 under anhydrous conditions, compared with the traditional modification method of simply physically encapsulating silane coupling agent in aqueous phase, the chemically bonded coupling agent molecules will not desorb during subsequent resin mixing and shearing processes, thus solving the problem of graphene being prone to agglomeration and difficult to disperse in coatings due to its extremely high surface energy.

[0017] 2. By combining waterborne acrylic emulsion with waterborne epoxy resin emulsion, the acrylic component compensates for the poor flexibility and easy cracking of the epoxy component, while the epoxy component compensates for the low crosslinking density and insufficient chemical resistance of the acrylic component, thus achieving a coating with high hardness, strong adhesion, excellent flexibility and impact resistance.

[0018] 3. By using water-based acrylic emulsion and water-based epoxy resin emulsion as the main film-forming substances and deionized water as the dispersion medium, the organic solvents in traditional graphene anti-corrosion coatings are replaced. The coating formulation has extremely low VOC content, making it environmentally friendly and harmless to the health of construction workers. Attached Figure Description

[0019] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a photograph of the anti-corrosion coating obtained in Example 1 of the present invention, taken during a salt spray resistance test. Figure 2 This is a photograph of the anti-corrosion coating obtained in Comparative Example 1, taken during a salt spray resistance test. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of the present invention.

[0022] This invention provides a graphene anti-corrosion coating, comprising the following raw materials in parts by weight: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts waterborne acrylic emulsion, 30-40 parts waterborne epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter.

[0023] This invention provides a water-based graphene anti-corrosion coating containing only trace amounts of volatile organic compounds, offering the advantages of being environmentally friendly and pollution-free. In the raw material system, water serves as the dispersion medium, providing a uniform mixing environment for all components. Graphene, with its two-dimensional sheet structure, can extend the penetration paths of corrosive media such as water molecules, oxygen, and chloride ions, thereby improving the coating's anti-corrosion and anti-permeability capabilities. Water-based acrylic emulsion and water-based epoxy resin are the film-forming resin components in the graphene anti-corrosion coating system. The water-based acrylic emulsion provides the coating with excellent weather resistance, flexibility, and adhesion. The epoxy groups in the epoxy resin molecule have high reactivity; after ring-opening crosslinking, they can form a highly dense three-dimensional network structure, resulting in high coating hardness, strong anti-permeability, and excellent resistance to corrosive media such as acids, alkalis, and salt spray. The epoxy resin and acrylic emulsion are used in combination; the epoxy component compensates for the insufficient crosslinking density and hardness of the acrylic component, while the acrylic component compensates for the poor flexibility and weather resistance of the epoxy component. When the amount of acrylic emulsion is less than 12 parts, the coating lacks flexibility and weather resistance; when it is more than 20 parts, the proportion of epoxy component is relatively reduced, resulting in a decrease in the overall crosslinking density of the coating, and a weakening of hardness and chemical resistance. When the amount of waterborne epoxy resin emulsion is less than 30 parts, the coating crosslinking density is insufficient and the compactness decreases; when it is more than 40 parts, the stability of the coating system decreases, and the coating film has poor flexibility, making it prone to microcracks when subjected to alternating hot and cold temperatures or substrate deformation, which in turn provides channels for corrosive media.

[0024] Rust-preventive pigments are mainly zinc-containing pigments. When the dosage is less than 12 parts, the concentration of rust-preventive active substances in the coating is insufficient, resulting in limited active corrosion protection. When the dosage is more than 20 parts, the pigment volume concentration is too high, leading to decreased coating density and insufficient resin to completely coat the pigment particles. This weakens the coating's cohesion, making it prone to chalking and peeling. Film-forming aids lower the minimum film-forming temperature of the resin emulsion, helping latex particles to fully deform and fuse during water evaporation, forming a continuous and dense coating film and avoiding defects such as pinholes and cracks caused by poor film formation. By adjusting the dosage of film-forming aids, good film quality can be obtained under different construction ambient temperatures. Leveling agents reduce the surface tension of the coating, improving its leveling and wetting / spreading ability on the substrate during construction, eliminating surface defects such as brush marks and orange peel, obtaining a smooth and flat coating surface, and improving the coating's appearance quality and protective uniformity. Water-based coatings are rich in water and organic resins, making them prone to bacterial and mold growth during storage, leading to mold, deterioration, foul odor, and viscosity changes. Adding bactericides and disinfectants can inhibit microbial growth and extend the shelf life of coatings. Adhesion promoters are used to enhance the interfacial bonding between the coating and the metal substrate, improve the adhesion of the coating on various metal substrates, prevent the coating from peeling off due to insufficient adhesion, and thus ensure the durability of the anti-corrosion effect.

[0025] Furthermore, the preparation process of modified graphene is as follows: 6 parts by weight of graphene powder, 0.6-1.2 parts by weight of silane coupling agent and 0.02-0.05 parts by weight of catalyst are dispersed in anhydrous organic solvent, heated to 100-110℃ under nitrogen protection, and 0.05-0.15 parts by weight of water are slowly added while stirring. The reaction is carried out at a constant temperature for 2-4 hours. After the reaction, the graphene is washed and dried to obtain modified graphene.

[0026] Graphene's high surface energy makes it highly prone to agglomeration in resin matrices. Poor dispersion not only fails to enhance the shielding effect but also creates defects in the coating, leading to localized corrosion. Therefore, graphene needs to be modified by introducing organic functional groups onto its surface to reduce surface energy and increase its chemical affinity with the resin matrix, thereby improving the uniformity of graphene dispersion.

[0027] Graphene powder is prepared by physical exfoliation. Its edges and defects contain a small number of oxygen-containing functional groups such as hydroxyl and carboxyl groups. These sites can chemically bond with the hydrolysis products of silane coupling agents. If the amount of coupling agent is too low, it is insufficient to fully cover the active sites on the graphene surface, resulting in insufficient grafting density, insignificant modification effect, and the graphene is still prone to partial agglomeration during subsequent storage and use. If the amount of coupling agent is too high, unreacted coupling agent molecules may undergo self-condensation on the graphene surface, forming an excessively thick polysiloxane layer. This not only wastes raw materials but may also weaken the intrinsic excellent shielding properties of graphene due to over-coating.

[0028] The rate at which water is added needs to be controlled during the reaction. The reaction of alkoxy groups of the coupling agent to generate silanol groups is carried out step by step. If a large amount of water is added at once, it will cause a large number of coupling agent molecules to hydrolyze and condense with each other at the same time, which will seriously reduce the grafting efficiency of graphene.

[0029] The reaction temperature is close to the boiling point of the solvent toluene, and reflux is used during the reaction.

[0030] Furthermore, the graphene powder raw materials used in the modified graphene have an average sheet diameter of 1-3 μm and a thickness of 1-5 nm.

[0031] The ideal graphene sheet diameter is between 1-3 μm. While smaller sheets are easier to disperse, the shielding area of ​​a single sheet is limited. Achieving a comparable shielding effect requires a larger addition amount, but excessive addition increases costs and coating viscosity. Furthermore, smaller-diameter graphene sheets create a barrier layer with more edge points, providing more pathways for water molecules to diffuse through these gaps, potentially limiting overall shielding efficiency. Conversely, larger sheets significantly increase the difficulty of dispersing in the coating. Even with surface modification, excessively large graphene sheets are difficult to fully dissociate and distribute uniformly under shear forces, easily forming folds, curls, or accumulations in the coating, creating stress concentration points and penetration channels, which ultimately reduces the overall anti-corrosion performance of the coating.

[0032] Furthermore, the silane coupling agent is KH560, the catalyst is dibutyltin dilaurate, and the anhydrous organic solvent is toluene. Furthermore, the washing process involves three washes with anhydrous ethanol, and the drying process involves vacuum drying at 60°C for 8 hours.

[0033] Furthermore, the waterborne acrylic emulsion has a solid content of 45%, and the waterborne epoxy resin emulsion has an epoxy equivalent of 450-550 g / eq and a solid content of 50%.

[0034] When the solid content of waterborne acrylic emulsions is significantly lower than 45%, the effective solids of the acrylic resin introduced into the system decrease, resulting in an insufficient proportion of acrylic component in the final dry film of the coating. This weakens the coating's flexibility and adhesion. Simultaneously, the increased moisture introduced into the coating system leads to excessively low viscosity, causing sagging during application and requiring the addition of thickeners, thus increasing the complexity and cost of the formulation. If the solid content is significantly higher than 45%, although the acrylic solids are sufficient, the particle size distribution and viscosity characteristics of high-solid-content acrylic emulsions are often unfavorable for the adsorption and coating of graphene on the particle surface in subsequent steps. When the epoxy equivalent of the epoxy resin is too low, its curing shrinkage rate is large, resulting in a brittle and inflexible coating. The significant difference in modulus between the epoxy resin and the acrylic component easily generates internal stress at the phase interface or coating-substrate interface, which can lead to cracking or peeling of the coating in severe cases. When the epoxy equivalent is too high, the flexibility of the resin molecular chains increases, which is beneficial for improving the coating's impact resistance and ability to follow substrate deformation. However, insufficient crosslinking density reduces the coating's density and is detrimental to resistance to the penetration of small-molecule corrosive media.

[0035] Furthermore, the anti-rust pigment is a mixture of zinc phosphate and aluminum tripolyphosphate, wherein the mass ratio of zinc phosphate to aluminum tripolyphosphate is 1:(0.5-1).

[0036] Furthermore, the film-forming aid is dodecyl alcohol ester, the leveling agent is polydimethylsiloxane, the bactericide and disinfectant is isothiazolinone, and the adhesion promoter is epoxy phosphate ester.

[0037] The present invention also provides a method for preparing the above-mentioned graphene anti-corrosion coating, comprising the following steps: (1) Weigh the following raw materials according to the following weight proportions: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts water-based acrylic emulsion, 30-40 parts water-based epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter; (2) Add the modified graphene powder weighed in step (1) to 20-30 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 200-400 r / min for 10-20 min, and then disperse ultrasonically at 500-800 W and 20-40 kHz for 1-2 h to obtain modified graphene aqueous dispersion; (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with a pH adjuster, then stir at 200-400 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 20-40 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 500-700 r / min for 20-40 minutes, then increase the speed to 700-1000 r / min, slowly add the A material obtained in step (3), and continue to disperse for 30-60 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 12-48 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0038] Furthermore, the pH adjuster in step (3) is 2-amino-2-methyl-1-propanol.

[0039] The present invention will be further described in detail below with reference to specific embodiments.

[0040] Example 1

[0041] A graphene anti-corrosion coating comprises the following raw materials in parts by weight: 40 parts deionized water, 2 parts modified graphene, 16 parts waterborne acrylic emulsion, 35 parts waterborne epoxy resin emulsion, 16 parts anti-rust pigment, 2 parts film-forming aid dodecyl alcohol ester, 0.1 parts leveling agent polydimethylsiloxane, 0.2 parts bactericide and disinfectant isothiazolinone, and 0.5 parts adhesion promoter epoxy phosphate ester.

[0042] The rust-preventive pigment is a mixture of zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:0.7.

[0043] The preparation process of modified graphene is as follows: Six parts by weight of graphene powder with an average sheet diameter of 1-3 μm and a thickness of 1-5 nm, 0.8 parts by weight of silane coupling agent KH560, and 0.03 parts by weight of catalyst dibutyltin dilaurate were dispersed in anhydrous toluene. The mixture was heated to 105 °C under nitrogen protection, and 0.1 parts by weight of water was slowly added with stirring. The reaction was carried out at a constant temperature for 3 hours. After the reaction, the mixture was washed three times with anhydrous ethanol and then dried under vacuum at 60 °C for 8 hours to obtain modified graphene.

[0044] A method for preparing a graphene anti-corrosion coating includes the following steps: (1) Weigh the above raw materials according to the weight proportions; (2) Add the modified graphene powder weighed in step (1) to 25 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 300 r / min for 15 min, and then ultrasonically disperse at 700 W and 30 kHz for 1.5 h to obtain modified graphene aqueous dispersion. (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with the pH adjuster 2-amino-2-methyl-1-propanol, then stir at 300 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 30 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 600 r / min for 30 minutes, then increase the speed to 900 r / min, slowly add the A material obtained in step (3), and continue to disperse for 45 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 24 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0045] Example 2

[0046] A graphene anti-corrosion coating comprises the following raw materials in parts by weight: 35 parts deionized water, 1.5 parts modified graphene, 12 parts waterborne acrylic emulsion, 30 parts waterborne epoxy resin emulsion, 12 parts anti-rust pigment, 1.5 parts film-forming aid dodecyl alcohol ester, 0.05 parts leveling agent polydimethylsiloxane, 0.1 parts bactericide and disinfectant isothiazolinone, and 0.3 parts adhesion promoter epoxy phosphate ester.

[0047] The rust-preventive pigment is a mixture of zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:0.5.

[0048] The preparation process of modified graphene is as follows: Six parts by weight of graphene powder with an average sheet diameter of 1-3 μm and a thickness of 1-5 nm, 0.6 parts by weight of silane coupling agent KH560, and 0.02 parts by weight of catalyst dibutyltin dilaurate were dispersed in anhydrous toluene. The mixture was heated to 100 °C under nitrogen protection, and 0.05 parts by weight of water were slowly added with stirring. The reaction was carried out at a constant temperature for 2 hours. After the reaction, the mixture was washed three times with anhydrous ethanol and then dried under vacuum at 60 °C for 8 hours to obtain modified graphene.

[0049] A method for preparing a graphene anti-corrosion coating includes the following steps: (1) Weigh the above raw materials according to the weight proportions; (2) Add the modified graphene powder weighed in step (1) to 20 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 200r / min for 20min, and then ultrasonically disperse at 500W power and 20kHz frequency for 2h to obtain modified graphene aqueous dispersion. (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with the pH adjuster 2-amino-2-methyl-1-propanol, then stir at 200 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 40 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 500 r / min for 40 minutes, then increase the speed to 700 r / min, slowly add the A material obtained in step (3), and continue to disperse for 60 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 12 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0050] Example 3

[0051] A graphene anti-corrosion coating comprises the following raw materials in parts by weight: 45 parts deionized water, 2.5 parts modified graphene, 20 parts waterborne acrylic emulsion, 40 parts waterborne epoxy resin emulsion, 20 parts anti-rust pigment, 3 parts film-forming aid dodecyl alcohol ester, 0.2 parts leveling agent polydimethylsiloxane, 0.3 parts bactericide and disinfectant isothiazolinone, and 0.8 parts adhesion promoter epoxy phosphate ester.

[0052] The rust-preventive pigment is a mixture of zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:1.

[0053] The preparation process of modified graphene is as follows: Six parts by weight of graphene powder with an average sheet diameter of 1-3 μm and a thickness of 1-5 nm, 1.2 parts by weight of silane coupling agent KH560, and 0.05 parts by weight of catalyst dibutyltin dilaurate were dispersed in anhydrous toluene. The mixture was heated to 110 °C under nitrogen protection, and 0.15 parts by weight of water were slowly added with stirring. The reaction was carried out at a constant temperature for 4 hours. After the reaction, the mixture was washed three times with anhydrous ethanol and then dried under vacuum at 60 °C for 8 hours to obtain modified graphene.

[0054] A method for preparing a graphene anti-corrosion coating includes the following steps: (1) Weigh the above raw materials according to the weight proportions; (2) Add the modified graphene powder weighed in step (1) to 30 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 400 r / min for 10 min, and then ultrasonically disperse at 800 W and 40 kHz for 1 h to obtain modified graphene aqueous dispersion. (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with the pH adjuster 2-amino-2-methyl-1-propanol, then stir at 400 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 20 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 700 r / min for 20 minutes, then increase the speed to 1000 r / min, slowly add the A material obtained in step (3), and continue to disperse for 30 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 48 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0055] Example 4

[0056] A graphene anti-corrosion coating comprises the following raw materials in parts by weight: 42 parts deionized water, 2.1 parts modified graphene, 18 parts waterborne acrylic emulsion, 38 parts waterborne epoxy resin emulsion, 15 parts anti-rust pigment, 2.5 parts film-forming aid dodecyl alcohol ester, 0.15 parts leveling agent polydimethylsiloxane, 0.15 parts bactericide and disinfectant isothiazolinone, and 0.6 parts adhesion promoter epoxy phosphate ester.

[0057] The rust-preventive pigment is a mixture of zinc phosphate and aluminum tripolyphosphate in a mass ratio of 1:0.6.

[0058] The preparation process of modified graphene is as follows: Six parts by weight of graphene powder with an average sheet diameter of 1-3 μm and a thickness of 1-5 nm, one part by weight of silane coupling agent KH560, and 0.04 parts by weight of catalyst dibutyltin dilaurate were dispersed in anhydrous toluene. The mixture was heated to 105 °C under nitrogen protection, and 0.12 parts by weight of water were slowly added with stirring. The reaction was carried out at a constant temperature for 2.5 hours. After the reaction, the mixture was washed three times with anhydrous ethanol and then dried under vacuum at 60 °C for 8 hours to obtain modified graphene.

[0059] A method for preparing a graphene anti-corrosion coating includes the following steps: (1) Weigh the above raw materials according to the weight proportions; (2) Add the modified graphene powder weighed in step (1) to 30 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 350 r / min for 20 min, and then ultrasonically disperse at 550 W and 35 kHz for 2 h to obtain modified graphene aqueous dispersion. (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with the pH adjuster 2-amino-2-methyl-1-propanol, then stir at 350 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 40 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 650 r / min for 40 minutes, then increase the speed to 900 r / min, slowly add the A material obtained in step (3), and continue to disperse for 60 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 30 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

[0060] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the raw material components of the coating do not contain modified graphene. During coating preparation, all components are directly mixed and dispersed evenly, followed by aging and filtration.

[0061] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the graphene in the raw material components of the coating is unmodified ordinary graphene. The preparation steps of the coating are the same as those in Example 1.

[0062] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that when modifying graphene, graphene is directly mixed with silane coupling agent and then dispersed. The specific process is as follows: add silane coupling agent to deionized water and disperse it evenly. After dispersion, maintain the rotation speed and add graphene powder to continue to disperse evenly.

[0063] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the average diameter of the graphene powder used is 0.2-0.5 μm and the thickness is 8-15 nm.

[0064] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that only zinc phosphate is used in the anti-rust pigment.

[0065] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that only aluminum tripolyphosphate is used in the rust-preventive pigment.

[0066] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that in the preparation of the coating, all raw materials were directly mixed and stirred and dispersed at 700 r / min for 40 minutes, then ultrasonically dispersed at 800 W and 40 kHz for 2 hours, and then aged at room temperature for 48 hours. The coating was then passed through a 200-mesh filter to obtain the final product.

[0067] Compare with Example 1 Comparative Example 1 uses commercially available water-based anti-corrosion coatings.

[0068] The performance of the anti-corrosion coatings in Examples 1-4, Comparative Examples 1-7, and Control Example 1 was tested, including: The salt spray resistance of anti-corrosion coatings was tested according to GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes".

[0069] The adhesion of anti-corrosion coatings was tested according to GB / T 9286-2021 "Cross-cut test for paints and varnishes".

[0070] The water resistance of anti-corrosion coatings was tested according to Method A of GB / T 1733-1993 "Determination of Water Resistance of Coating Films".

[0071] The performance test results of the coatings obtained in Examples 1-4 are shown in Table 1: Table 1

[0072] The performance test results of the coatings obtained in Comparative Examples 1-7 and Control Example 1 are shown in Table 2: Table 2

[0073] As can be seen from the data in Tables 1 and 2, the graphene anti-corrosion coating provided by the present invention has excellent salt spray resistance, water resistance and adhesion.

[0074] The coating in Comparative Example 1 does not contain modified graphene, and its salt spray resistance is only 450 hours, with an adhesion rating of level 2. The paint film relies entirely on resin and anti-rust pigments for protection. Without the assistance of modified graphene, water molecules and oxygen can penetrate relatively freely in the coating, reaching the substrate in a short period of time and causing corrosion. After the paint film blisters, its adhesion is drastically lost.

[0075] The salt spray resistance of Comparative Example 2 was increased to 574 hours, indicating that the introduction of graphene can indeed extend the penetration path of corrosive media. However, the surface of unmodified graphene lacks active functional groups and has extremely poor compatibility with the resin matrix. It cannot be stably dispersed in water and coating systems, resulting in severe agglomeration. These agglomerates not only fail to form an effective shielding network but also become defect points in the coating, causing the corrosive media to penetrate rapidly along the interface, and the paint film to quickly blister and peel off under immersion.

[0076] Comparative Example 3, which uses a common silane coupling agent to modify graphene by blending in water, achieved a salt spray resistance of 891 hours, which is better than Comparative Examples 1 and 2, but far inferior to the Example. This is because simple blending of the silane coupling agent and graphene only allows the coupling agent to adhere to the graphene surface through weak physical adsorption. This bond is easily desorbed during subsequent ultrasonic dispersion and resin mixing, causing the graphene to re-aggregate and lose its dispersibility and reactivity.

[0077] Comparative Example 4 uses graphene with small sheet diameter and multiple layers. Its salt spray resistance is significantly lower than that of Example 1. The sheet diameter is too small, resulting in insufficient shielding area of ​​a single sheet, which cannot effectively block the corrosion of external media. The thickness is too large, resulting in a very low aspect ratio. The interfacial compatibility between graphene microsheets with too many layers and resin is poor, which makes it easy to generate microcracks and permeation channels under water immersion conditions.

[0078] Comparative Examples 5 and 6 used single zinc phosphate and aluminum tripolyphosphate as anti-corrosion pigments, respectively, and the salt spray resistance of both was significantly reduced compared to Example 1.

[0079] Comparative Example 7, after mixing all raw materials in one batch, dispersed at high speed and ultrasonically treated, exhibited a salt spray resistance of only 795 hours, lower adhesion than the example, and failed the 15-day water resistance test. The one-pot mixing prevented graphene from being directionally adsorbed onto the surface of the acrylic emulsion particles. After curing, the graphene was randomly distributed and agglomerated, failing to form an effective shielding layer.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphene anti-corrosion coating, characterized in that, The raw materials include the following parts by weight: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts water-based acrylic emulsion, 30-40 parts water-based epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter.

2. The graphene anti-corrosion coating according to claim 1, characterized in that, The preparation process of the modified graphene is as follows: Six parts by weight of graphene powder, 0.6-1.2 parts by weight of silane coupling agent and 0.02-0.05 parts by weight of catalyst were dispersed in an anhydrous organic solvent. The mixture was heated to 100-110℃ under nitrogen protection, and 0.05-0.15 parts by weight of water were slowly added while stirring. The mixture was kept at a constant temperature for 2-4 hours. After the reaction, the mixture was washed and dried to obtain modified graphene.

3. The graphene anti-corrosion coating according to claim 2, characterized in that, The graphene powder raw material used in the modified graphene has an average sheet diameter of 1-3 μm and a thickness of 1-5 nm.

4. The graphene anti-corrosion coating according to claim 2, characterized in that, The silane coupling agent is KH560, the catalyst is dibutyltin dilaurate, and the anhydrous organic solvent is toluene.

5. The graphene anti-corrosion coating according to claim 2, characterized in that, The washing process involves three washes with anhydrous ethanol, followed by vacuum drying at 60°C for 8 hours.

6. The graphene anti-corrosion coating according to claim 1, characterized in that, The aqueous acrylic emulsion has a solid content of 45%, and the aqueous epoxy resin emulsion has an epoxy equivalent of 450-550 g / eq and a solid content of 50%.

7. The graphene anti-corrosion coating according to claim 1, characterized in that, The anti-rust pigment is a mixture of zinc phosphate and aluminum tripolyphosphate, wherein the mass ratio of zinc phosphate to aluminum tripolyphosphate is 1:(0.5-1).

8. The graphene anti-corrosion coating according to claim 1, characterized in that, The film-forming aid is dodecyl alcohol ester, the leveling agent is polydimethylsiloxane, the bactericide and disinfectant is isothiazolinone, and the adhesion promoter is epoxy phosphate ester.

9. A method for preparing a graphene anti-corrosion coating as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Weigh the following raw materials according to the following weight proportions: 35-45 parts deionized water, 1.5-2.5 parts modified graphene, 12-20 parts water-based acrylic emulsion, 30-40 parts water-based epoxy resin emulsion, 12-20 parts anti-rust pigment, 1.5-3 parts film-forming aid, 0.05-0.2 parts leveling agent, 0.1-0.3 parts bactericide and disinfectant, and 0.3-0.8 parts adhesion promoter; (2) Add the modified graphene powder weighed in step (1) to 20-30 parts by weight of deionized water, adjust the pH to 4.0-5.0 with acetic acid, stir at 200-400 r / min for 10-20 min, and then disperse ultrasonically at 500-800 W and 20-40 kHz for 1-2 h to obtain modified graphene aqueous dispersion; (3) Adjust the pH of the aqueous acrylic emulsion to 8.0-9.0 with a pH adjuster, then stir at 200-400 r / min and slowly add the modified graphene aqueous dispersion obtained in step (2). After the addition is complete, continue stirring for 20-40 minutes to allow the graphene to be adsorbed on the surface of the acrylic latex particles to obtain material A. (4) Mix the waterborne epoxy resin emulsion, anti-rust pigment, film-forming aid, leveling agent, bactericide, adhesion promoter and the remaining deionized water, stir and disperse at 500-700 r / min for 20-40 minutes, then increase the speed to 700-1000 r / min, slowly add the A material obtained in step (3), and continue to disperse for 30-60 minutes after adding. (5) The coating obtained in step (4) is aged at room temperature for 12-48 hours and then passed through a 200-mesh filter to obtain the graphene anti-corrosion coating.

10. The method for preparing the graphene anti-corrosion coating according to claim 9, characterized in that, The pH adjuster in step (3) is 2-amino-2-methyl-1-propanol.

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