Preparation method of polyaniline-doped graphene composite environmentally friendly water-based coating

Abstract

The present invention discloses a composite material in which polyaniline is uniformly polymerized on the surface of graphene for use in water-based anti-corrosion coatings. The method uses hydrogen peroxide as an initiator to gently and uniformly polymerize aniline on the surface of graphene at room temperature. The composite material maintains the original lamellar structure of graphene and effectively fills the defective holes in the coating curing process. Polyaniline is adsorbed on the graphene surface to form uniform protrusions, which increases the surface roughness and prolongs the penetration path of the corrosive medium. At the same time, polyaniline weakens the mutual stacking between graphene flakes, and graphene also effectively reduces the agglomeration of polyaniline during polymerization, synergistically improving the dispersibility and anti-permeation barrier properties of the composite in water-based epoxy resin coatings. There is a strong interaction between the composite material and the epoxy resin, which makes it have good compatibility and stability. Finally, the redox property of polyaniline can form a passivation film on the steel surface, further improving the anti-corrosion performance of the coating.

Description

Technical Field

[0001] The invention belongs to the field of preparation and application of metal anti-corrosion coatings, and relates to a preparation method and application of a polyaniline-doped graphene composite environmentally friendly water-based coating. Background Art

[0002] As metal corrosion poses increasing safety concerns, preventing it is crucial. Metal surface coatings are the most effective and widely used corrosion prevention method. Water-based coatings use water as a solvent, are free of volatile organic compounds, and are environmentally friendly. However, the presence of numerous hydrophilic groups and residual surfactants in water-based epoxy systems accelerates the penetration of corrosive ions and water molecules, weakening their barrier properties. Furthermore, the formation of pores and microporous defects during the curing process further reduces their impermeability, hindering their continued application.

[0003] Graphene's excellent chemical stability, rapid electrical conductivity, outstanding mechanical properties, and strong adhesion and film-forming properties with polymer resins can synergistically improve the overall performance of coatings. However, graphene coatings still face significant challenges in practical applications. The inherent incompatibility between graphene and polymers leads to poor dispersion and even agglomeration of graphene sheets, which hinders the "maze effect" of graphene to prevent the diffusion of corrosive media in the coating and even accelerates the entry of corrosive particles. In the field of corrosion protection, polyaniline has attracted widespread attention due to its advantages such as low cost, simple synthesis, good electrical conductivity, and good environmental stability. However, due to its rigid structure, polyaniline aggregates irregularly during chemical polymerization, resulting in agglomeration, which cannot effectively exert its barrier properties in the coating. Summary of the Invention

[0004] In order to overcome the disadvantages of graphene and polyaniline in anti-corrosion coatings, the present invention prepares a polyaniline-doped graphene composite material, so that polyaniline is uniformly polymerized along the graphene surface, exerting the synergistic effect of the two. The composite material is added as a filler to a water-based epoxy coating to improve its dispersibility, compatibility and barrier properties in the water-based anti-corrosion coating, thereby enhancing the durability and anti-corrosion performance of the coating.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0006] A method for preparing a polyaniline-doped graphene composite environmentally friendly water-based coating, the method comprising the following steps:

[0007] (S1) adding aniline to a hydrochloric acid solution and mixing and dissolving the mixture thoroughly, then uniformly mixing the aniline solution with the graphene dispersion, then adding hydrogen peroxide to the mixed solution for polymerization, and after the polymerization, filtering and washing the obtained polyaniline graphene composite material sample, and freeze-drying and collecting it.

[0008] (S2) After the polyaniline graphene composite material is uniformly dispersed in water, the composite dispersion is mixed with a water-based epoxy resin emulsion and stirred under vacuum conditions and then fully mixed. A water-based epoxy curing agent is added and the original sealing conditions are maintained and stirred evenly, and then the mixture is coated on the carbon steel surface and cured to obtain a polyaniline graphene composite coating.

[0009] Furthermore, the concentration of the graphene dispersion in step (S1) is 0.5 to 2 mg mL -1 , the volume is 20-200 mL. The amount of aniline added is 200-800 mg. The concentration of hydrochloric acid is 1 mol L -1 The volume is 20 mL. The amount of hydrogen peroxide added is 0.13-0.53 mL. The composite ratio of polyaniline to graphene dispersion is maintained at 5:1-20:1.

[0010] Furthermore, in step (S1), the dissolution time of aniline in hydrochloric acid is 30 to 60 minutes, the mixing time of aniline and graphene dispersion is 30 to 90 minutes, and the solution polymerization temperature is room temperature and the polymerization time is 12 to 24 hours.

[0011] Furthermore, the graphene dispersion in step (S1) is graphene or graphene oxide. The structure of the polyaniline graphene composite material is a rough lamellar structure in which uniform polyaniline particles grow on the wrinkled surface of the graphene.

[0012] Furthermore, in step (S2), the polyaniline graphene composite material is uniformly dispersed in water using ultrasonic dispersion for 2 to 4 hours, with a water mass of 1 to 3 grams. The aqueous epoxy resin emulsion and the composite mixture are mixed under vacuum stirring for 2 to 5 hours while maintaining a sealed state under the action of a vacuum pump. The aqueous epoxy curing agent and the aqueous epoxy resin mixture are mixed under vacuum stirring for 20 to 60 minutes.

[0013] Furthermore, in step (S2), the composite coating is applied automatically or manually, with a thickness of 30 to 40 μm. The composite coating is cured for 4 to 8 days at room temperature and 6 to 24 hours at high temperature, with a high-temperature curing temperature of 65 to 85°C.

[0014] Furthermore, in step (S2), the mass ratio of the water-based epoxy emulsion to the water-based epoxy curing agent is 2:1. The solids content of the water-based epoxy emulsion is maintained at 50-53%, and the solids content of the water-based epoxy curing agent is maintained at 42-46%. The mass of the added composite material is calculated based on the solids content. The mass fraction of the added polyaniline-graphene composite material is 0.1-1%.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] 1. The composite maintains the original lamellar structure of graphene, and polyaniline is adsorbed on the graphene surface to form uniform protrusions, which effectively fills the defective holes in the coating curing process, extends the penetration path of the corrosive medium, and improves the coating's impermeability.

[0017] 2. Polyaniline weakens the stacking of graphene sheets, and graphene also effectively reduces the agglomeration phenomenon during polyaniline polymerization, synergistically improving the dispersibility of the composite in water-based epoxy resin coatings.

[0018] 3. The strong interaction between the polyaniline-graphene composite and epoxy resin results in excellent compatibility and stability. The redox properties of polyaniline form a passivating film on the steel surface, further enhancing the coating's corrosion resistance. The polyaniline-graphene composite waterborne epoxy coating exhibits excellent density and impermeability, demonstrating satisfactory long-term corrosion protection.

[0019] 4. During the preparation process, the coating uses water as the solvent, no organic solvents are used, and there are no volatile organic compounds, which is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The surface SEM morphology of the polyaniline graphene oxide composite material of Example 1 is shown.

[0021] Figure 2 The surface SEM morphology of the polyaniline graphene oxide composite material of Example 2 is shown.

[0022] Figure 3 The surface SEM morphology of the polyaniline-graphene oxide composite material of Example 3 is shown.

[0023] Figure 4 The surface SEM morphology of the polyaniline-graphene oxide composite material of Example 4 is shown.

[0024] Figure 5 The surface SEM morphology of the coating prepared in Comparative Example 1 is shown.

[0025] Figure 6 The surface SEM morphology of the coating prepared in Example 3 is shown.

[0026] Figure 7 The electrochemical impedance spectroscopy (EIM) values ​​of the coatings prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 3 are shown.

[0027] Figure 8 The Tafel polarization curves of the coatings prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 3 are shown.

[0028] Figure 9The electrochemical impedance spectroscopy (EIM) values ​​of the coatings prepared in Example 1, Example 2, Example 3, and Example 4 are shown.

[0029] Figure 10 The Tafel polarization curves of the coatings prepared in Example 1, Example 2, Example 3, and Example 4 are shown.

[0030] Figure 11 The electrochemical impedance spectroscopy (EIM) values ​​of the coatings prepared in Example 3, Example 5, Example 6, and Example 7 are shown.

[0031] Figure 12 The Tafel polarization curves of the coatings prepared in Example 3, Example 5, Example 6, and Example 7 are shown.

[0032] Figure 13 The graph shows the change in electrochemical impedance modulus of the coatings prepared in Example 3, Example 5, Example 6, and Example 7 after long-term immersion in a 3.5% by mass sodium chloride solution. DETAILED DESCRIPTION

[0033] The preparation method and application of the composite coating will be further described in detail below with reference to the examples and drawings, but the embodiments of the present invention are not limited thereto.

[0034] Example 1

[0035] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 1 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, and 200 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.13 mL of 30% hydrogen peroxide was then added and polymerized at room temperature for 24 hours. The mixture was filtered, washed three times, and freeze-dried for later use. 10.8 mg of polyaniline-graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of a water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove air bubbles from the emulsion and the flask. The mixture was sealed and stirred for 3 hours. 2.5 g of a water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired viscous epoxy resin slurry. The prepared polyaniline-graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, the slurry was completely cured in a 70°C forced air oven for 12 hours, resulting in a coating thickness of 35 ± 2 μm. The polyaniline-graphene weight ratio at this point was 5:1.

[0036] Example 2

[0037] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 2 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, 400 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.27 mL of 30% hydrogen peroxide was then added and polymerized at room temperature for 24 hours. The mixture was filtered, washed three times, and freeze-dried for later use. 10.8 mg of polyaniline-graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of a water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove air bubbles from the emulsion and the flask. The mixture was sealed and stirred for 3 hours. 2.5 g of a water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired viscous epoxy resin slurry. The prepared polyaniline-graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, the slurry was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 35 ± 2 μm. The polyaniline-graphene ratio at this point was 10:1.

[0038] Example 3

[0039] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 3 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, and 600 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.4 mL of 30% hydrogen peroxide was then added and polymerized at room temperature for 24 hours. The mixture was filtered, washed three times, and freeze-dried for later use. 10.8 mg of polyaniline-graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of a water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove air bubbles from the emulsion and the flask. The mixture was sealed and stirred for 3 hours. 2.5 g of a water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired viscous epoxy resin slurry. The prepared polyaniline-graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, the slurry was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 35 ± 2 μm. The polyaniline-graphene weight ratio at this point was 15:1.

[0040] Example 4

[0041] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 4 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, 800 mg of aniline was added to 20 mL, 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.53 mL of 30% hydrogen peroxide was then added and polymerized at room temperature for 24 hours. The mixture was filtered, washed three times, and freeze-dried for later use. 10.8 mg of polyaniline-graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of a water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove air bubbles from the emulsion and the flask. The mixture was sealed and stirred for 3 hours. 2.5 g of a water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired viscous epoxy resin slurry. The prepared polyaniline-graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, the slurry was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 30 ± 2 μm. The polyaniline-graphene weight ratio at this point was 20:1.

[0042] Example 5

[0043] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 5 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, and 600 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.4 mL of hydrogen peroxide (30%) was then added and polymerized at room temperature for 24 hours. The mixture was filtered and washed three times, then freeze-dried and collected for later use. 3.6 mg of polyaniline-graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove bubbles in the emulsion and the bottle. The mixture was sealed and stirred for 3 hours. 2.5 g of water-based epoxy curing agent was then added and stirred under vacuum conditions for 30 minutes to obtain the desired epoxy resin viscous slurry for later use. The prepared polyaniline-graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, it was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 35 ± 2 μm. The added mass of the polyaniline-graphene composite material at this time was 0.1%.

[0044] Example 6

[0045] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in Example 6 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, and 600 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.4 mL of hydrogen peroxide (30%) was then added and polymerized at room temperature for 24 hours. The mixture was filtered and washed three times, then freeze-dried and collected for later use. 18 mg of polyaniline graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove bubbles in the emulsion and the flask. The mixture was sealed and stirred for 3 hours. 2.5 g of water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to form the desired epoxy resin viscous slurry. The prepared polyaniline graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, it was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 30 ± 2 μm. The added mass of the polyaniline graphene composite material at this point was 0.5%.

[0046] Example 7

[0047] The preparation method of a polyaniline-doped graphene composite environmentally friendly water-based coating in this embodiment 7 comprises the following steps: taking 2 mg mL -1 20 mL of graphene oxide solution was ultrasonically dispersed for 2 h, and 600 mg of aniline was added to 20 mL of 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 30 minutes, then mixed with a graphene oxide solution and stirred for 30 minutes. 0.4 mL of hydrogen peroxide (30%) was then added and polymerized at room temperature for 24 hours. The mixture was filtered and washed three times, then freeze-dried and collected for later use. 36 mg of polyaniline graphene oxide composite powder was added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours. The solution was then mixed with 5 g of water-based epoxy resin emulsion in a single-necked flat-bottom flask and vacuum-treated for 10 minutes to remove bubbles in the emulsion and the bottle. The mixture was sealed and stirred for 3 hours. 2.5 g of water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired epoxy resin viscous slurry for later use. The prepared polyaniline graphene oxide water-based epoxy resin slurry was coated on a Q235 carbon steel surface using a wire rod coater. After drying at room temperature for 5 days, it was completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 35 ± 2 μm. The added mass of the polyaniline graphene composite material at this time was 1%.

[0048] Comparative Example 1

[0049] The blank water-based epoxy resin coating in Comparative Example 1 was prepared by mixing 2.5 g of water and 5 g of a water-based epoxy resin emulsion in a single-necked flat-bottom flask, vacuuming the mixture for 10 minutes to remove bubbles from the emulsion and the flask, and then sealing and stirring the mixture for 3 hours. 2.5 g of a water-based epoxy curing agent was then added and stirred under vacuum for 30 minutes to obtain the desired viscous epoxy resin slurry. The prepared water-based epoxy resin slurry was applied to a Q235 carbon steel surface using a wire rod coater, dried at room temperature for 5 days, and then completely cured in a 70°C forced air oven for 12 hours. The coating thickness was 35 ± 2 μm.

[0050] Comparative Example 2

[0051] The preparation method of the polyaniline waterborne epoxy resin coating in Comparative Example 2 comprises the following steps: adding 600 mg of aniline to 20 mL of 1 mol L -1 Stir in hydrochloric acid solution for 30 minutes, then add 0.4mL hydrogen peroxide (30%) and polymerize at room temperature for 24 hours, filter and wash 3 times, freeze-dry and collect for later use. Add 10.8mg polyaniline powder to a beaker containing 2.5g water and ultrasonically disperse for 2 hours. Then mix the solution with 5g water-based epoxy resin emulsion in a single-necked flat-bottom flask, vacuum treat for 10 minutes to remove bubbles in the emulsion and the bottle and seal and stir for 3 hours. Then add 2.5g water-based epoxy curing agent and stir under vacuum conditions for 30 minutes to obtain the required epoxy resin viscous slurry for later use. Use a wire rod coater to coat the prepared polyaniline graphene oxide water-based epoxy resin slurry on the surface of Q235 carbon steel. After drying at room temperature for 5 days, place it in a 70℃ forced air oven for 12 hours until it is completely cured. The coating thickness is 35±2μm.

[0052] Comparative Example 3

[0053] The preparation method of the graphene oxide water-based epoxy resin coating in this comparative example 3 is as follows: 10.8 mg of graphene oxide powder is added to a beaker containing 2.5 g of water and ultrasonically dispersed for 2 hours, then the solution is mixed with 5 g of water-based epoxy resin emulsion in a single-mouth flat-bottom flask, vacuum treated for 10 minutes to remove bubbles in the emulsion and the bottle, and sealed and stirred for 3 hours, and then 2.5 g of water-based epoxy curing agent is added and stirred under vacuum conditions for 30 minutes to obtain the required epoxy resin viscous slurry for use. The prepared polyaniline graphene oxide water-based epoxy resin slurry is coated on the surface of Q235 carbon steel using a wire rod coater, dried at room temperature for 5 days, and then completely cured in a 70°C blast oven for 12 hours. The coating thickness is 35±2 μm.

[0054] Test results:

[0055] Figure 1 This is the surface SEM morphology of the polyaniline graphene oxide composite material in Example 1. Figure 2This is the surface SEM morphology of the polyaniline graphene oxide composite material in Example 2. Figure 3 This is the surface SEM morphology of the polyaniline graphene oxide composite material in Example 3. Figure 4 This is the surface SEM morphology of the polyaniline graphene oxide composite material of Example 4. Figure 1 、 Figure 2 、 Figure 3 and Figure 4 From the comparison of the SEM morphologies of the polyaniline graphene composite materials in various examples, it can be seen that as the amount of polyaniline polymerization on the graphene surface continues to increase, uniformly polymerized particle protrusions are gradually formed to the optimal content in Example 3, a rough surface is constructed, and the hydrophobicity of the surface is improved, which is beneficial to blocking the infiltration of corrosive media, extending the diffusion path of corrosive media, and providing an effective basis for long-term corrosion protection of the coating.

[0056] Figure 5 This is the surface SEM morphology of the coating prepared in Comparative Example 1. Figure 6 The surface SEM morphology of the coating prepared in Example 3. Figure 5 and Figure 6 It can be seen that the surface of the blank coating in comparative example 1 has obvious defect holes, which is not conducive to blocking corrosion particles. The surface of Example 3 is smooth and dense, has obvious barrier properties to corrosive media, can effectively prevent their invasion, and improve the coating's impermeability and anti-corrosion properties.

[0057] The test results of the coating electrochemical parameters obtained in the above examples and comparative examples are as follows:

[0058] Table 1 Electrochemical parameters of different coating types

[0059]

[0060] Figure 7 Electrochemical impedance spectroscopy (EIM) diagrams of the coatings prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 3.

[0061] Figure 8 These are Tafel polarization curves of the coatings prepared in Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 3. Figure 9 Electrochemical impedance spectroscopy (EIS) diagrams of the coatings prepared in Example 1, Example 2, Example 3, and Example 4. Figure 10 These are the Tafel polarization curves of the coatings prepared in Example 1, Example 2, Example 3, and Example 4. Figure 11 Electrochemical impedance spectroscopy (EIS) diagrams of the coatings prepared in Example 3, Example 5, Example 6, and Example 7. Figure 12 The Tafel polarization curves of the coatings prepared in Example 3, Example 5, Example 6 and Example 7 are shown in Table 1. Figure 7, 8, 9, 10, 11 and 12. In the comparison of the electrochemical parameters of each embodiment and the comparative example, the coating of embodiment 3 has the highest corrosion voltage and the smallest corrosion current is as low as 10 -10 Acm -2 , showing the best anti-corrosion effect. From the electrochemical impedance modulus values ​​in the above figures, it can be further concluded that the impedance modulus value of Example 3 is the largest, which is an order of magnitude higher than that of the blank coating, demonstrating excellent corrosion resistance.

[0062] Figure 13 The electrochemical impedance modulus value changes of the coatings prepared in Example 3, Example 5, Example 6 and Example 7 after long-term immersion in 3.5% sodium chloride solution. Figure 13 In the long-term salt water immersion test, the impedance modulus of Example 3 has a stable value without a drastic decrease in magnitude, which further confirms the excellent long-term corrosion resistance and corrosion inhibition ability of Example 3 in harsh corrosive environments, and has obvious protection against corrosion damage to metals.

[0063] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a polyaniline-doped graphene composite environmentally friendly water-based coating, characterized in that: The following steps are involved: (S1) adding aniline to a hydrochloric acid solution and mixing and dissolving the mixture thoroughly, then uniformly mixing the aniline solution with the graphene dispersion, then adding hydrogen peroxide to the mixed solution for polymerization, and after the polymerization is completed, filtering and washing the obtained polyaniline graphene composite material sample, and freeze-drying and collecting; (S2) after the polyaniline graphene composite material is uniformly dispersed in water, the composite dispersion is mixed with a water-based epoxy resin emulsion and stirred under vacuum conditions and then fully mixed, a water-based epoxy curing agent is added and the original sealing conditions are maintained and stirred evenly, and then the mixture is coated on a carbon steel surface and cured to obtain a polyaniline graphene composite coating; The concentration of the graphene dispersion described in step (S1) is 0.5-2 mg mL -1 The volume is 20-200 mL, the amount of aniline added is 200-800 mg, and the concentration of hydrochloric acid is 1 mol L -1 , the volume is 20 mL, the amount of hydrogen peroxide added is 0.13-0.53 mL, and the composite ratio of polyaniline and graphene dispersion is maintained at 5:1-20:1; The dissolution time of aniline in hydrochloric acid in step (S1) is 30 to 60 minutes, the mixing time of aniline and graphene dispersion is 30 to 90 minutes, the temperature of solution polymerization is room temperature, and the polymerization time is 12 to 24 hours; The graphene dispersion described in step (S1) is graphene or graphene oxide, and the structure of the polyaniline graphene composite material is a rough lamellar structure in which uniform polyaniline particles grow on the wrinkled surface of the graphene.

2. The method for preparing the polyaniline-doped graphene composite environmentally friendly water-based coating according to claim 1, characterized in that: In step (S2), the polyaniline graphene composite material is uniformly dispersed by ultrasonic dispersion in water, the ultrasonic time is 2 to 4 hours, the mass of water is 1 to 3 g, the water-based epoxy resin emulsion and the composite material mixture are mixed under vacuum stirring conditions of maintaining sealed stirring for 2 to 5 hours under the action of a vacuum pump, and the water-based epoxy curing agent and the water-based epoxy resin mixture are mixed under the action of a vacuum pump with stirring time of 20 to 60 minutes.

3. The method for preparing the polyaniline-doped graphene composite environmentally friendly water-based coating according to claim 1, characterized in that: The composite coating in step (S2) is applied automatically or manually with a thickness of 30 to 40 μm. The composite coating is cured at room temperature for 4 to 8 days and at high temperature for 6 to 24 hours at a temperature of 65 to 85°C.

4. The method for preparing the polyaniline-doped graphene composite environmentally friendly water-based coating according to claim 1, wherein: In step (S2), the mass ratio of the water-based epoxy emulsion to the water-based epoxy curing agent is 2:1, the solid content of the water-based epoxy emulsion oxygen is maintained at 50-53%, the solid content of the water-based epoxy curing agent is maintained at 42-46%, the added mass of the composite material is calculated based on the solid content, and the added mass fraction of the polyaniline graphene composite material is 0.1-1%.

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