Graphene functional coating as well as preparation method and spraying method thereof

Abstract

The invention relates to the technical field of anticorrosive coatings, and provides a graphene functional coating as well as a preparation method and a spraying method thereof. The graphene functional coating provided by the invention comprises a component A and a component B, the component A comprises modified graphene, zinc-aluminum mixed turbid liquid and waterborne epoxy resin, and the component B is a curing agent. The graphene functional coating provided by the invention is good in dispersity and stability, high in coating density, good in corrosion resistance, high in bonding strength with a base material and long in salt spray resistance life, and the waterborne epoxy resin is selected as a raw material, so that the harm to the environment and human bodies is reduced. The plasma spray gun with the circular seam nozzle is adopted for spraying, required energy is low, construction is convenient, and the plasma spray gun is suitable for various workpiece shapes and coating equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coatings, and in particular to a graphene functional coating and a preparation method and a spraying method thereof. Background Art

[0002] Materials such as metals and concrete are prone to corrosion, which can cause economic losses, huge consumption of resources, and aggravate environmental pollution. Therefore, anti-corrosion research, especially heavy anti-corrosion research, is gaining more and more attention from countries around the world. Among various anti-corrosion measures, coating anti-corrosion is the most economical, practical and convenient, and has received much attention from industry insiders.

[0003] Traditional anti-corrosion coatings include epoxy resin anti-corrosion coatings, polyurethane anti-corrosion coatings and zinc-rich anti-corrosion coatings. Most of them are solvent-based coatings, which use organic solvents as dispersion media. A large amount of organic volatiles are present during use, which can cause harm to human health and the environment during construction and application. Environmental protection has always been an important factor that has plagued the development of the coatings industry. Water-based coatings with low VOC content, powder coatings, high solids, and solvent-free coatings are currently advocated coatings. However, solvent-based coatings have better anti-corrosion properties. The water-based anti-corrosion coatings currently on the market are difficult to compete with solvent-based coatings in terms of anti-corrosion performance, and the salt spray resistance time is less than half of that of solvent-based coatings, resulting in a relatively low proportion of water-based anti-corrosion coatings.

[0004] Graphene is a two-dimensional sheet-like nanomaterial in which carbon atoms are connected in the form of sp2 hybridization. The thickness of a single layer is only 0.35nm, making it the thinnest material currently available. Graphene has many excellent properties, such as high tensile strength (~130GPa), high Young's modulus (~1.0TPa), high electrical conductivity (~108S·m -1 ), high thermal conductivity (~5000W·m -1 ·K -1 ), high specific surface area (~2600m 2 / g) and high barrier properties. However, when graphene is applied to water-based coatings, it is difficult to disperse evenly, and the anti-corrosion performance of current water-based graphene coatings is still poor and difficult to meet the requirements of use. Summary of the invention

[0005] In view of this, the present invention provides a graphene functional coating and a preparation method and a spraying method thereof. The graphene functional coating provided by the present invention is a water-based coating with good environmental protection, good dispersibility and stability, good corrosion resistance and long salt spray resistance time.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A graphene functional coating comprises a component A and a component B; the component A comprises the following components in mass fractions: 45-50% of modified graphene, 30-35% of zinc-aluminum mixed suspension, and 15-20% of waterborne epoxy resin;

[0008] The modified graphene includes one or both of copper-plated graphene and fluorinated graphene oxide;

[0009] The zinc-aluminum mixed suspension comprises the following components by mass fraction: 15-25% of silane coupling agent, 18-32% of zinc powder, 6-15% of aluminum powder, 8-12% of corrosion inhibitor, 10-12% of dispersant, and 4-43% of water; the pH value of the zinc-aluminum mixed suspension is 9-10;

[0010] The B component is a curing agent.

[0011] Preferably, the preparation method of the copper-plated graphene comprises the following steps: mixing a graphene oxide dispersion, copper sulfate and ascorbic acid for reduction reaction to obtain the copper-plated graphene; the reduction reaction temperature is 80 to 90° C., the time is 2 to 3 hours, and the pH value is 9 to 10.

[0012] Preferably, the preparation method of the fluorinated graphene oxide comprises the following steps: mixing graphene oxide, water, nitric acid and hydrofluoric acid for hydrothermal reaction to obtain the fluorinated graphene oxide; the temperature of the hydrothermal reaction is 120 to 160° C. and the time is 10 to 12 hours.

[0013] Preferably, the silane coupling agent includes one or more of n-octyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane; the zinc powder is flaky zinc powder; the aluminum powder is flaky aluminum powder; the particle size of the flaky zinc powder is 80 to 100 microns; the particle size of the flaky aluminum powder is 80 to 100 microns; the corrosion inhibitor is molybdate; and the dispersant is Tween.

[0014] Preferably, the preparation method of the zinc-aluminum mixed suspension comprises the following steps: mixing a silane coupling agent and water, adjusting the pH value of the resulting coupling agent solution to 9-10, then adding zinc powder and aluminum powder for ultrasonic dispersion, and then adding a corrosion inhibitor and a dispersant to obtain the zinc-aluminum mixed suspension.

[0015] Preferably, the water-based epoxy resin is a bisphenol A type water-based epoxy resin; and the curing agent is a polyamine water-based epoxy curing agent.

[0016] The present invention also provides a method for preparing the graphene functional coating according to the above scheme, comprising the following steps:

[0017] The modified graphene, the zinc-aluminum mixed suspension and the water-based epoxy resin are mixed to obtain a component A;

[0018] The component A and the component B are mixed and allowed to stand for defoaming to obtain the graphene functional coating.

[0019] The present invention also provides a method for spraying the graphene functional coating according to the above scheme, comprising the following steps:

[0020] The graphene functional coating is sprayed on the surface of the substrate by using a spraying device; the spraying device is a plasma spray gun, and the nozzle of the plasma spray gun is an annular gap nozzle.

[0021] Preferably, the spraying conditions include: the feed gas pressure is 5-5.5 kgf / cm 2 , the feeding speed is 2.5-3.0L / min, the distance between the muzzle and the substrate surface is 30-50mm, the moving speed of the muzzle is 300-350mm / s, the heating temperature is 80-120℃, and the spraying thickness is 0.05-0.15mm.

[0022] Preferably, the annular gap nozzle includes a nozzle body, a secondary air ring is arranged at the center of the nozzle body, the nozzle body and the secondary air ring are combined to form an annular air cavity, and an annular gap is formed at the front end of the nozzle body; a guide sleeve is arranged at the center of the secondary air ring, and a gap is formed between the guide sleeve and the inner wall of the secondary air ring; an air inlet is arranged on the side wall of the nozzle body, and the air inlet is connected to the air inlet pipe; and an auxiliary air hole is arranged on the side wall of the secondary air ring.

[0023] The invention provides a graphene functional coating, comprising a component A and a component B; the component A comprises the following components in mass fractions: 45-50% of modified graphene, 30-35% of a zinc-aluminum mixed suspension, and 15-20% of a water-based epoxy resin; the modified graphene comprises one or two of copper-plated graphene and fluorinated graphene oxide; the zinc-aluminum mixed suspension comprises the following components in mass fractions: 15-25% of a silane coupling agent, 18-32% of zinc powder, 6-15% of aluminum powder, 8-12% of a corrosion inhibitor, 10-12% of a dispersant, and 4-43% of water; the pH value of the zinc-aluminum mixed suspension is 9-10; and the component B is a curing agent. The present invention adopts modified graphene (copper-plated graphene and / or fluorinated graphene oxide) as raw material, can realize uniform dispersion of graphene in coating, utilizes small size effect and two-dimensional sheet structure of graphene, can effectively fill defects in coating, improve density of coating, and form overlapping "labyrinth" physical shielding layer, effectively prevent water molecules from contacting substrate through coating; when corrosive medium contacts substrate, metal will preferentially form passivation layer at coating-substrate interface, avoid further corrosion of substrate; and the graphene functional coating of the present invention also includes zinc-aluminum mixed suspension, wherein zinc powder and aluminum powder can play the role of sacrificial anode, thereby protecting cathode material (i.e. substrate), and zinc powder and aluminum powder can also form dense protective film on substrate surface, prevent corrosive medium from entering substrate; at the same time, the present invention selects water-based epoxy resin as raw material, reduces the generation of VOC from source, and reduces harm to environment and human body. In summary, the graphene functional coating provided by the present invention has good dispersibility and stability, high coating density, good corrosion resistance, high bonding strength with the substrate, long salt spray resistance life, low VOC content, and little harm to the environment and human body.

[0024] The present invention also provides a method for spraying the graphene functional coating described in the above scheme. The present invention uses a plasma spray gun for spraying. Compared with the traditional cold spraying of coatings, the coating can not only be applied more evenly on the surface of the parts, but also has good coating quality and strong bonding with the substrate; the spraying method provided by the present invention is convenient to construct and is suitable for various workpiece shapes and coating equipment; and the traditional plasma spray gun uses a Laval nozzle, while the plasma spray gun used in the present invention is an annular gap nozzle. The use of an annular gap nozzle can improve the spraying efficiency, moderate energy (the coating and the substrate are physically combined, rather than the welding of traditional plasma spraying), and good uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the preparation principle of fluorinated graphene oxide;

[0026] Figure 2Schematic diagram of the structure of the annular gap nozzle, wherein 1 is the air inlet pipe, 2 is the nozzle body, 3 is the annular cavity, 4 is the guide sleeve, 5 is the auxiliary air hole, and 6 is the secondary air ring;

[0027] Figure 3 Schematic diagram of a plasma spray gun, wherein 7 is a gas inlet, 8 is a coating material feeding port, 9 is an auxiliary heating device, 10 is a spray layer, 11 is a substrate, 12 is a particle flow formed by the coating, and 13 is a power source;

[0028] Figure 4 is a schematic diagram of the spraying process;

[0029] Figure 5 The following are scanning electron microscope (SEM) images of the coatings obtained on different substrate surfaces, where (a) and (a1) are coatings on steel substrate surfaces, (b) and (b1) are coatings on concrete substrate surfaces, and (c) and (c1) are coatings on aluminum substrate surfaces. DETAILED DESCRIPTION

[0030] The present invention provides a graphene functional coating, comprising component A and component B; the component A comprises the following components by mass fraction: 45-50% of modified graphene, 30-35% of zinc-aluminum mixed suspension, and 15-20% of waterborne epoxy resin;

[0031] The modified graphene includes one or both of copper-plated graphene and fluorinated graphene oxide;

[0032] The zinc-aluminum mixed suspension comprises the following components by mass fraction: 15-25% of silane coupling agent, 18-32% of zinc powder, 6-15% of aluminum powder, 8-12% of corrosion inhibitor, 10-12% of dispersant, and 4-43% of water; the pH value of the zinc-aluminum mixed suspension is 9-10;

[0033] The B component is a curing agent.

[0034] Unless otherwise specified, all raw materials / components used in the present invention are commercially available.

[0035] In terms of mass fraction, component A in the graphene functional coating of the present invention includes 45-50% of modified graphene, preferably 45%, 46%, 48% or 50%; the modified graphene is one or both of copper-plated graphene and fluorinated graphene oxide.

[0036] In the present invention, the preparation method of the copper-plated graphene preferably comprises the following steps: mixing a graphene oxide dispersion, copper sulfate and ascorbic acid for reduction reaction to obtain the copper-plated graphene; the preparation method of the graphene oxide dispersion is preferably: ultrasonically dispersing graphene powder in N-methylpyrrolidone to obtain a graphene oxide dispersion; the temperature of the ultrasonic dispersion is preferably room temperature, and the time is preferably 3 to 4 hours; the purity of the N-methylpyrrolidone is preferably 99.9wt%; the amount ratio of the graphene oxide, copper sulfate and ascorbic acid is preferably 1 to 2g: 0.1 to 0.5mol: 2 to 4g.

[0037] In the present invention, the temperature of the reduction reaction is preferably 80-90°C, the time is preferably 2-3h, and the pH value is preferably 9-10; the present invention preferably first adjusts the pH value of the graphene oxide dispersion to 9-10, and then adds copper sulfate and ascorbic acid to carry out the reduction reaction; the reagent used to adjust the pH value is preferably NaOH solution, and the concentration of the NaOH solution is preferably 40-50g / L.

[0038] After the reduction reaction is completed, the present invention preferably filters the obtained reaction solution and then washes it to obtain the copper-plated graphene. The present invention coats the surface of graphene with copper to promote uniform dispersion of graphene in the coating and avoid agglomeration.

[0039] In the present invention, the preparation method of the fluorinated graphene oxide preferably includes the following steps: mixing graphene oxide, water, nitric acid and hydrofluoric acid for hydrothermal reaction to obtain the fluorinated graphene oxide; the temperature of the hydrothermal reaction is preferably 160°C, and the time is preferably 12 hours; the mass ratio of the graphene oxide, nitric acid and hydrofluoric acid is preferably 0.3-0.5:1:1; the nitric acid is commercially available concentrated nitric acid (65-69wt%), and the hydrofluoric acid is commercially available hydrofluoric acid (35-40wt%); the water is preferably deionized water; after the hydrothermal reaction is completed, the obtained reaction solution is preferably filtered, and the obtained solid product is washed and filtered to obtain the fluorinated graphene oxide. The schematic diagram of the preparation principle of the fluorinated graphene oxide is as follows Figure 1 The present invention fluorinates the graphene oxide, can etch the graphene surface, and introduces fluorine (F) functional groups into the graphene to improve the adhesion of the graphene.

[0040] In terms of mass fraction, component A in the graphene functional coating of the present invention includes 30-35% of a zinc-aluminum mixed suspension, preferably 30%, 32%, 34% or 35%; the zinc-aluminum mixed suspension preferably includes the following components in mass fractions: 15-25% of a silane coupling agent, preferably 18-22%, 18-32% of zinc powder, preferably 20-28%, 6-15% of aluminum powder, preferably 8-12%, 8-12% of a corrosion inhibitor, preferably 9-11%, 10-12% of a dispersant, preferably 11-12%, and 4-43% of water, preferably 5-40%; the pH value of the zinc-aluminum mixed suspension is preferably 9-10.

[0041] In the present invention, the silane coupling agent preferably includes one or more of n-octyltriethoxysilane, n-octyltriethoxysilane, γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and γ-methacryloxypropyltrimethoxysilane (KH570); the zinc powder is preferably flaky zinc powder; the aluminum powder is preferably flaky aluminum powder; the particle size of the flaky zinc powder is preferably 80 to 100 microns; the particle size of the flaky aluminum powder is preferably 80 to 100 microns; the corrosion inhibitor is preferably molybdate, more preferably sodium molybdate; the dispersant is preferably Tween, more preferably one or both of Tween-20 and Tween-80.

[0042] In the present invention, the preparation method of the zinc-aluminum mixed suspension preferably includes the following steps: mixing a silane coupling agent and water, adjusting the pH value of the obtained coupling agent solution to 9-10, then adding zinc powder and aluminum powder for ultrasonic dispersion, and then adding a corrosion inhibitor and a dispersant to obtain the zinc-aluminum mixed suspension; the reagent used to adjust the pH value of the coupling agent solution is preferably ammonia water; the power of the ultrasonic dispersion is preferably 80W, and the ultrasonic time is preferably 30-60min.

[0043] In terms of mass fraction, component A in the graphene functional coating of the present invention includes 15-20% of a water-based epoxy resin, preferably 15%, 16%, 18% and 20%; the water-based epoxy resin is preferably a bisphenol A type water-based epoxy resin, specifically one or both of epoxy resin E44 and epoxy resin E51.

[0044] The graphene functional coating provided by the present invention comprises a component B; the component B is a curing agent, and the curing agent is preferably a polyamine waterborne epoxy curing agent; the present invention has no special requirements on the specific type of the polyamine waterborne epoxy curing agent, and commercially available products can be used, such as a modified polyamine epoxy curing agent, and the modified polyamine epoxy curing agent can be specifically SFA (amino hydrogen equivalent 48 g / mol), PSPA (amino hydrogen equivalent 65 g / mol) or APS (amino hydrogen equivalent 62 g / mol).

[0045] In the present invention, the mass ratio of the component A to the component B is preferably 75-85:15-20; in a specific embodiment of the present invention, the component A and the component B are packaged separately during storage and transportation, and are mixed before spraying.

[0046] The present invention also provides a method for preparing the graphene functional coating according to the above scheme, comprising the following steps:

[0047] The modified graphene, the zinc-aluminum mixed suspension and the water-based epoxy resin are mixed to obtain a component A;

[0048] The component A and the component B are mixed and allowed to stand for defoaming to obtain the graphene functional coating.

[0049] In the present invention, the modified graphene, zinc-aluminum mixed suspension and water-based epoxy resin are preferably mixed by stirring (referred to as the first stirring and mixing) and ultrasonic mixing in sequence; the component A and the component B are preferably mixed by stirring (referred to as the second stirring and mixing); the rates of the first stirring and mixing and the second stirring and mixing are independently preferably 800 to 1500 r / min, and the stirring time is preferably 15 to 30 min; the static defoaming is preferably based on the static defoaming until the coating viscosity is 15 to 20 s.

[0050] The present invention also provides a method for spraying the graphene functional coating according to the above scheme, comprising the following steps:

[0051] The graphene functional coating is sprayed on the surface of the substrate by using a spraying device; the spraying device is a plasma spray gun, and the nozzle of the plasma spray gun is an annular gap nozzle.

[0052] In the present invention, the substrate is a metal substrate or a concrete substrate; the metal substrate may specifically be a steel substrate or an aluminum substrate.

[0053] In the present invention, the spraying conditions preferably include: the feed gas pressure is preferably 5 to 5.5 kgf / cm 2 The feeding speed is preferably 2.5-3.0 L / min, the distance between the muzzle and the substrate surface is preferably 30-50 mm, the moving speed of the muzzle is preferably 300-350 mm / s, the heating temperature is preferably 80-120°C, the spraying thickness is preferably 0.05-0.15 mm, more preferably 0.10-0.15 mm; the feeding gas is preferably air.

[0054] The graphene functional coating of the present invention contains more zinc powder and aluminum powder. The present invention adopts a plasma spray gun and sprays at a certain heating temperature and speed, which can ensure that the zinc-aluminum mixed powder and the substrate have a high bonding force, and no subsequent post-treatment is required, and it can be directly cured at room temperature; while the traditional coating containing metal powder needs to be heated and kept warm at a certain temperature and time after spraying. The spraying method provided by the present invention does not require subsequent treatment, is simpler to operate, and has higher spraying efficiency.

[0055] In the present invention, the nozzle of the plasma spray gun is an annular gap nozzle, and the structural schematic diagram is as shown in Figure 2 shown.

[0056] In the present invention, the annular gap nozzle includes a nozzle body 2, a secondary air ring 6 is arranged at the center of the nozzle body 2, the nozzle body 2 and the secondary air ring 6 are combined to form an annular air cavity 3, and an annular gap is formed at the front end of the nozzle body 2; a guide sleeve 4 is arranged at the center of the secondary air ring 6, and a gap is formed between the guide sleeve 4 and the inner wall of the secondary air ring 6; an air inlet is arranged on the side wall of the nozzle body 2, and the air inlet is connected to the air inlet pipe 1; an auxiliary air hole 5 is arranged on the side wall of the secondary air ring 6.

[0057] In a specific embodiment of the present invention, the annular air cavity is a special-shaped structure, specifically shrinking from the side wall of the nozzle body to the front end of the nozzle body.

[0058] In a specific embodiment of the present invention, the nozzle body 2 and the secondary air ring 6 are coaxially arranged, and the outer wall of the secondary air ring 6 is arc-shaped; the number of the auxiliary air holes 5 is preferably 4 to 6; in the cross-section of the annular gap nozzle, the extension lines of the center lines of the two gap profiles form an angle α, and the value of α is 45°.

[0059] In the present invention, the structural schematic diagram of the plasma spray gun is as follows Figure 3 The schematic diagram of the spraying process is shown in Figure 4 As shown below; combined Figure 3-4 Provide explanation.

[0060] In the present invention, the plasma spray gun includes a front gun body and a rear gun body, a nozzle is fixed in the front gun body, a cathode is fixed in the rear gun body, the nozzle is connected to the positive pole of the power supply, and the cathode is connected to the negative pole of the power supply; an auxiliary heating device is also provided at the nozzle outlet of the plasma spray gun; the auxiliary heating device is preferably a resistance heating device; the auxiliary heating device is provided in the present invention, which can ensure the spraying temperature of the coating and is conducive to the combination of the coating and the substrate.

[0061] In a specific embodiment of the present invention, after the working gas and the coating are introduced into the plasma spray gun, the arc generated between the cathode and the nozzle heats the working gas and ionizes it into a high-temperature plasma. The plasma heats the coating, and a particle flow formed by the coating liquid is ejected from the nozzle. The ejected particle flow is sprayed under the heating conditions of the auxiliary heating device to form a coating on the surface of the substrate.

[0062] In the present invention, a wet coating is obtained after spraying, and the wet coating is preferably cured at room temperature for 20 to 24 hours to obtain a coating.

[0063] The comparison results of the graphene functional coating of the present invention and the common coating in the art are shown in Table 1.

[0064] Table 1 Comparison results of graphene functional coatings of the present invention and common coatings in the art

[0065]

[0066]

[0067] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] Example 1

[0069] Preparation of copper-plated graphene: 1 g of graphene powder was dispersed in 99.9 wt% N-methylpyrrolidone and ultrasonically dispersed at room temperature for 3 h to obtain a graphene oxide dispersion. The pH value of the graphene oxide dispersion was adjusted to 9 using 40 g / L NaOH solution. Then 0.2 mol of copper sulfate and 3 g of ascorbic acid were added to the graphene oxide dispersion in turn, the mixture was reacted at 80 ° C for 2 h, filtered, and washed to obtain copper-plated graphene.

[0070] Preparation of zinc-aluminum mixed suspension: n-octyltriethoxysilane is added to water and stirred, and the pH value of the solution is adjusted to 10 with ammonia water; dry flaky zinc powder and flaky aluminum powder are weighed and added to the coupling agent solution, ultrasonically dispersed at a power of 80 W for 30 minutes, and then sodium molybdate and Tween 20 are added to obtain a zinc-aluminum mixed suspension; in the zinc-aluminum mixed suspension, the mass fraction of the silane coupling agent is 15%, the mass fraction of the zinc powder is 25%, the mass fraction of the aluminum powder is 10%, the mass fraction of the sodium molybdate is 10%, and the mass fraction of the dispersant is 10%.

[0071] Preparation of graphene functional coating: Copper-plated graphene, zinc-aluminum mixed suspension and water-based epoxy resin (E51) are stirred and ultrasonically mixed to obtain component A, in which the mass fraction of copper-plated graphene is 50%, the mass fraction of zinc-aluminum mixed suspension is 30%, and the mass fraction of water-based epoxy resin is 20%.

[0072] A commercially available polyamine epoxy curing agent (SFA, amino hydrogen equivalent 48 g / mol) was used as component B, and component A and component B were mixed in a mass ratio of 80:20, stirred evenly again, and allowed to stand and defoam until the viscosity was 15 to 20 s to obtain a functional graphene coating.

[0073] Spraying: Apply the above coatings Figure 3 The plasma spray gun shown (the nozzle is an annular gap nozzle, the structure is as shown in Figure 2 As shown in the figure, spray it on the substrate, adjust the voltage and current of the spraying equipment, and control the feeding gas (air) pressure to 5kgf / cm 2 , the feeding speed is 3.0L / min, the distance between the gun and the substrate surface is 3mm, the moving speed of the gun is 300mm / s, the heating temperature is 80℃; the spraying thickness is controlled at 120μm; finally, the coating is cured at room temperature for 24h to obtain the coating. The substrates used for spraying are 45 steel substrate, concrete substrate and 6061 aluminum substrate. Figure 5 The following are scanning electron microscope (SEM) images of the coatings obtained on different substrate surfaces, where (a) and (a1) are coatings on steel substrate surfaces, (b) and (b1) are coatings on concrete substrate surfaces, and (c) and (c1) are coatings on aluminum substrate surfaces. Figure 5 It can be seen that the coating of the present invention has a relatively high density on the surfaces of different substrates.

[0074] Example 2

[0075] Preparation of fluorinated graphene oxide (FGO): Graphene oxide is dispersed in deionized water, followed by adding HNO3 and HF and stirring evenly; the mixed solution is transferred to a hydrothermal autoclave and reacted at 160°C for 12 hours; finally, the obtained product is washed, filtered and dried to obtain FGO, wherein the mass ratio of graphene oxide, HNO3 and HF is 0.5:1:1.

[0076] The preparation method of the zinc-aluminum mixed suspension is the same as that of Example 1, except that the silane coupling agent is replaced by KH550, and the mass fraction of the silane coupling agent, the mass fraction of the zinc powder, the mass fraction of the aluminum powder, the mass fraction of the sodium molybdate, and the mass fraction of the dispersant in the zinc-aluminum mixed suspension are controlled to be 25%, 32%, 6%, 8%, and 12%.

[0077] The preparation method of the graphene functional coating is the same as that of Example 1, except that the mass fraction of fluorinated graphene oxide in component A is controlled to be 45%, the mass fraction of the zinc-aluminum mixed suspension is controlled to be 35%, and the mass fraction of the waterborne epoxy resin is controlled to be 20%.

[0078] The spraying method was the same as that in Example 1. After spraying, the coating was cured at room temperature for 24 hours to obtain a coating.

[0079] Comparative Example 1

[0080] The other conditions were the same as those in Example 1, except that the zinc-aluminum mixed solution was not added, and the other components were the same.

[0081] Comparative Example 2

[0082] The zinc-aluminum mixed liquid in Example 1 is used as a coating, without modified graphene, water-based epoxy resin and curing agent, and the preparation method of the zinc-aluminum mixed suspension is the same as that in Example 1.

[0083] Performance Testing

[0084] The viscosity, dispersibility and stability of the coatings prepared in Examples 1 to 2 were tested, and the bonding strength, hardness, salt spray resistance life, coating notch electrochemical impedance and coating self-corrosion current density of the coating obtained on 45 steel were tested at the same time. The coating viscosity was tested with reference to GB / T 1723-1993 "Determination of coating viscosity", the bonding strength of the coating and the substrate was tested with reference to GB / T 9286-1998 "Scratch test of paint and varnish film", the salt spray resistance life was tested with reference to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test", the coating electrochemical impedance was tested with reference to GB / T 39482.3-2020 "Electrochemical impedance spectroscopy (EIS) of painted and unpainted metal specimens Part 3: Processing and analysis of data obtained from simulated electrolytic cells", the coating self-corrosion current density was tested with reference to GB / T 40299-2021 "Applicable practice for electrochemical measurement methods for corrosion tests of metals and alloys", and the coating stability test reference standard was GB / T 6753.3-1986 (Test method for storage stability of coatings). The results are shown in Table 2.

[0085] Table 2 Performance test results

[0086]

[0087] According to the data in Table 2, it can be seen that the graphene functional coating prepared by the present invention has good dispersibility and stability, high bonding strength with the substrate, long salt spray resistance life, and good corrosion resistance. At the same time, the coating of the present invention does not contain organic solvents, has good environmental protection, and has broad application prospects; the coating in Comparative Example 1 does not contain zinc-aluminum mixed suspension, and only zinc-aluminum mixed suspension is used as the coating in Comparative Example 2. The bonding strength, hardness, salt spray resistance life, etc. of the obtained coating are significantly reduced, and the corrosion resistance is poor.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A graphene functional coating, characterized in that: It comprises component A and component B; the component A comprises the following components in mass fractions: 45-50% of modified graphene, 30-35% of zinc-aluminum mixed suspension, and 15-20% of waterborne epoxy resin; The modified graphene includes one or both of copper-plated graphene and fluorinated graphene oxide; The zinc-aluminum mixed suspension comprises the following components by mass fraction: 15-25% of silane coupling agent, 18-32% of zinc powder, 6-15% of aluminum powder, 8-12% of corrosion inhibitor, 10-12% of dispersant, and 4-43% of water; the pH value of the zinc-aluminum mixed suspension is 9-10; The B component is a curing agent.

2. The graphene functional coating according to claim 1, characterized in that: The preparation method of the copper-plated graphene comprises the following steps: mixing a graphene oxide dispersion, copper sulfate and ascorbic acid for reduction reaction to obtain the copper-plated graphene; the temperature of the reduction reaction is 80-90° C., the time is 2-3 hours, and the pH value is 9-10.

3. The graphene functional coating according to claim 1, characterized in that: The preparation method of the fluorinated graphene oxide comprises the following steps: mixing graphene oxide, water, nitric acid and hydrofluoric acid for hydrothermal reaction to obtain the fluorinated graphene oxide; the temperature of the hydrothermal reaction is 120-160° C. and the time is 10-12 hours.

4. The graphene functional coating according to claim 1, characterized in that: The silane coupling agent includes one or more of n-octyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane; the zinc powder is flaky zinc powder; the aluminum powder is flaky aluminum powder; the particle size of the flaky zinc powder is 80 to 100 microns; the particle size of the flaky aluminum powder is 80 to 100 microns; the corrosion inhibitor is molybdate; and the dispersant is Tween.

5. The graphene functional coating according to claim 1 or 4, characterized in that: The preparation method of the zinc-aluminum mixed suspension comprises the following steps: mixing a silane coupling agent and water, adjusting the pH value of the obtained coupling agent solution to 9-10, then adding zinc powder and aluminum powder for ultrasonic dispersion, and then adding a corrosion inhibitor and a dispersant to obtain the zinc-aluminum mixed suspension.

6. The graphene functional coating according to claim 1, characterized in that: The water-based epoxy resin is a bisphenol A type water-based epoxy resin; the curing agent is a polyamine water-based epoxy curing agent.

7. The method for preparing the graphene functional coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: The modified graphene, the zinc-aluminum mixed suspension and the water-based epoxy resin are mixed to obtain a component A; The component A and the component B are mixed and allowed to stand for defoaming to obtain the graphene functional coating.

8. The method for spraying the graphene functional coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: The graphene functional coating is sprayed on the surface of the substrate by using a spraying device; the spraying device is a plasma spray gun, and the nozzle of the plasma spray gun is an annular gap nozzle.

9. The spraying method according to claim 8, characterized in that: The spraying conditions include: the feed gas pressure is 5-5.5 kgf / cm 2 , the feeding speed is 2.5-3.0L / min, the distance between the muzzle and the substrate surface is 30-50mm, the moving speed of the muzzle is 300-350mm / s, the heating temperature is 80-120℃, and the spraying thickness is 0.05-0.15mm.

10. The spraying method according to claim 8, characterized in that: The annular gap nozzle comprises a nozzle body (2), a secondary air ring (6) is arranged at the center of the nozzle body (2), the nozzle body (2) and the secondary air ring (6) are combined to form an annular air cavity (3), and an annular gap is formed at the front end of the nozzle body (2); a guide sleeve (4) is arranged at the center of the secondary air ring (6), and a gap is formed between the guide sleeve (4) and the inner wall of the secondary air ring (6); an air inlet is arranged on the side wall of the nozzle body (2), and the air inlet is connected to the air inlet pipe (1); and an auxiliary air hole (5) is arranged on the side wall of the secondary air ring (6).

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