Graphene modified Dacromet coating and preparation method thereof

Abstract

The invention relates to the field of metal anticorrosive paint, in particular to graphene modified Dacromet paint and a preparation method thereof. The graphene modified Dacromet coating comprises the following raw materials in parts by mass: 20-30 parts of zinc powder, 5-10 parts of aluminum powder, 15-30 parts of composite slurry, 8-15 parts of a film-forming agent, 1-10 parts of an auxiliary agent and the balance of deionized water, wherein the total parts by mass of the raw materials are 100; the composite slurry comprises functionalized graphene, silica powder, a silane coupling agent and deionized water, wherein the functionalized graphene is obtained by modifying graphene oxide with polyoxyalkylene amine. According to the chromium-free Dacromet coating, the problems that a traditional chromium-free Dacromet coating is low in coating abrasion resistance and hardness are effectively solved, on the basis, the formula is more environmentally friendly, the obtained Dacromet coating has excellent coating abrasion resistance, hardness and compactness, the coating has excellent corrosion resistance, and the protective performance of the coating is comprehensively improved.

Description

Technical Field

[0001] This application relates to the field of metal anti-corrosion coatings, specifically to a graphene-modified Dacromet coating and its preparation method. Background Technology

[0002] Dacromet coating, also known as Dacromet, Dacromet Rust, or Dacromet in some regions, and domestically as zinc-chromium coating, is an anti-corrosion coating primarily composed of zinc powder, aluminum powder, chromic acid, and deionized water. Compared to traditional electroplating zinc anti-corrosion processes, Dacromet coating offers superior corrosion resistance, high-temperature resistance, and no hydrogen embrittlement, making it widely used in the automotive, aerospace, and power industries.

[0003] Because traditional Dacromet coatings contain highly toxic and carcinogenic hexavalent chromium, they pose a threat to human health and the environment during use. Consequently, various countries have enacted regulations to strictly limit the chromium content in Dacromet coatings. Given these shortcomings of traditional Dacromet coatings, the development of chromium-free Dacromet coatings is currently in demand in the market. The core of chromium-free Dacromet is the elimination of carcinogenic hexavalent chromium from traditional Dacromet coatings. It utilizes environmentally friendly film-forming substances such as silane coupling agents, resins, and molybdates. The resulting silver-gray composite coating combines physical shielding and electrochemical protection, reducing toxicity and environmental pollution while retaining the excellent properties of traditional Dacromet coatings.

[0004] However, chromium-free Dacromet coatings still suffer from low wear resistance and hardness, which can easily affect their anti-corrosion performance. Currently, the common approach is to apply an additional high-hardness, abrasion-resistant coating over the Dacromet surface, a complex process. Furthermore, this additional high-hardness, abrasion-resistant coating is often thick, limiting its application range and potentially leading to uneven coating and insufficient adhesion. Therefore, there is an urgent need to develop a chromium-free Dacromet coating with excellent wear resistance and high hardness. Summary of the Invention

[0005] To overcome the problems of low wear resistance and hardness of chromium-free Dacromet coatings and improve the anti-corrosion performance of coatings, this application provides a graphene-modified Dacromet coating and its preparation method.

[0006] In a first aspect, this application provides a graphene-modified Dacromet coating, employing the following technical solution: A graphene-modified Dacromet coating comprises the following raw materials in parts by weight: The mixture comprises 20-30 parts zinc powder, 5-10 parts aluminum powder, 15-30 parts composite slurry, 8-15 parts film-forming agent, 1-10 parts additives, and deionized water to bring the total to 100 parts. The composite slurry includes functionalized graphene, silicon micropowder, silane coupling agent, and deionized water. The functionalized graphene is obtained by modifying graphene oxide with polyoxyethylene amine.

[0007] By adopting the above technical solution, this application firstly eliminates the carcinogenic hexavalent chromium in traditional Dacromet coatings, and the coating formulation does not introduce any significantly toxic raw materials. Furthermore, the formulation system uses deionized water as a solvent, effectively reducing the toxicity and environmental pollution caused by the volatilization of organic solvents. Therefore, the resulting water-based chromium-free Dacromet coating is more environmentally friendly. In addition, the Dacromet coating obtained in this application has excellent coating wear resistance and hardness, effectively overcoming the problem of low wear resistance and hardness in traditional chromium-free Dacromet coatings, thereby effectively improving the anti-corrosion performance of the coating.

[0008] More specifically, graphene consists of a single layer of carbon atoms arranged in sp... 2 Hybridization forms a hexagonal honeycomb planar structure, classifying it as a two-dimensional material. Its unique structure endows it with a large specific surface area and chemical inertness, while also possessing high electrical and thermal conductivity, high strength, and high toughness. Silica powder exhibits excellent temperature resistance, acid and alkali corrosion resistance, high impedance, and chemical stability, making it significant for improving the wear resistance and hardness of coatings. Therefore, graphene and silica powder have gradually become popular modifying raw materials in the coating industry. However, both graphene and silica powder are prone to agglomeration, making it difficult to form a uniform dispersion system. This results in poor coating density, susceptibility to defects, and even accelerated penetration of corrosive media.

[0009] To overcome the tendency of graphene and silicon powder to agglomerate, the graphene and silicon powder added in this application are firstly present in the form of a composite slurry. Pre-dispersion of the graphene and silicon powder is achieved under the action of a silane coupling agent, allowing them to be stably dispersed in the composite slurry system. Simultaneously, the functionalized graphene in this application is obtained by modifying graphene oxide with polyoxyenamine. Polyoxyenamine can react with the epoxy functional groups on the surface of graphene oxide, thereby achieving functional modification of the graphene oxide. Due to the excellent water solubility, emulsifying and dispersing properties, thickening, and foam stabilizing properties of polyoxyenamine, the dispersion uniformity of graphene oxide is further optimized after modification. Furthermore, polyoxyenamine can improve coating adhesion and durability in coating systems.

[0010] Building upon the effective overcoming of agglomeration issues, uniformly dispersed functionalized graphene, influenced by its layered structure, promotes the formation of coatings with excellent hardness, wear resistance, and density. It also establishes conductive pathways within the coating, granting it electrochemical inertness and enabling zinc-aluminum cathodic protection, thus helping to suppress electrochemical corrosion. Furthermore, uniformly dispersed silica powder synergistically forms a denser and more continuous physical barrier with functionalized graphene, resulting in coatings with superior hardness, wear resistance, and density. Simultaneously, the high impedance characteristics of silica powder enhance the coating's shielding ability against corrosive media, helping to achieve a balance between impedance and conductivity, thereby effectively suppressing galvanic corrosion and reducing the problem of poor corrosion protection due to sacrificial anodes. In summary, this application effectively overcomes the problems of low wear resistance and hardness in chromium-free Dacromet coatings, while also making the formulation more environmentally friendly. Simultaneously, the uniformly dispersed functionalized graphene and silicon micropowder work synergistically to improve the coating's hardness, wear resistance, and density, resulting in excellent corrosion resistance and comprehensively enhancing the coating's protective performance.

[0011] Preferably, the preparation method of the functionalized graphene includes the following steps: adding graphene oxide to deionized water and dispersing it ultrasonically to obtain an aqueous solution of graphene oxide; adding polyoxyethylene amine to the aqueous solution of graphene oxide and mixing and stirring to obtain a mixed solution; centrifuging the mixed solution, retaining the supernatant, and then vacuum drying to obtain functionalized graphene.

[0012] By adopting the above technical solution, the epoxy functional groups on the surface of graphene oxide undergo a nucleophilic substitution reaction with polyoxyethylene amines, making the functionalization modification process relatively simple and meeting the needs of industrial production. Furthermore, the solvent used in the reaction system is deionized water, which is more environmentally friendly.

[0013] Preferably, the additives include a polytetrafluoroethylene emulsion and a dispersant, wherein the particle size of the polytetrafluoroethylene emulsion is 50-100 nm.

[0014] By adopting the above technical solutions, polytetrafluoroethylene (PTFE) exhibits excellent corrosion resistance, high and low temperature resistance, and aging resistance. Furthermore, it can lower the curing temperature of coatings to a certain extent, helping to reduce structural damage to functionalized graphene caused by excessively high temperatures, which is significant for improving the performance of coatings. PTFE also has a low coefficient of friction, effectively reducing the coefficient of friction of the coating and improving its wear resistance. Simultaneously, under the influence of the nano-effect, PTFE emulsion can fill the pores of the coating to a certain extent, thus contributing to improving the density of the coating.

[0015] Preferably, the preparation method of the composite slurry includes the following steps: mixing functionalized graphene and deionized water to obtain a functionalized graphene aqueous solution; mixing silicon micropowder, silane coupling agent and deionized water, then adding the functionalized graphene aqueous solution, and mixing and stirring to obtain the composite slurry.

[0016] By adopting the above technical solution, since functionalized graphene already possesses good dispersibility, silicon micropowder is preferentially dispersed in a silane coupling agent and deionized water system to promote uniform dispersion of the silicon micropowder. Adding a pre-dispersed functionalized graphene aqueous solution on this basis effectively reduces silicon micropowder agglomeration, allowing the functionalized graphene and silicon micropowder in the composite slurry to form a uniform and stable dispersion system. Furthermore, using a silane coupling agent to assist in the dispersion of silicon micropowder before adding functionalized graphene can also promote the entry of silicon micropowder into the interlayer structure of functionalized graphene to a certain extent, forming a structurally stable cross-linked network under the action of the silane coupling agent. This has a positive effect on improving the density and hardness of the coating, thereby enhancing the anti-corrosion performance of the coating.

[0017] Preferably, the silane coupling agent is composed of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane in a mass ratio of 1:(1.3-2.5).

[0018] By adopting the above technical solution, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidyl etheroxypropyltrimethoxysilane can effectively combine silicon micropowder and functionalized graphene, improve the dispersion effect, and the effect is better when used in combination according to the above ratio.

[0019] Preferably, the composite slurry further includes modified multi-walled carbon nanotubes, which are obtained by modifying multi-walled carbon nanotube raw materials with sodium polystyrene sulfonate.

[0020] By adopting the above technical solution, it is further preferred to add modified multi-walled carbon nanotubes to the composite slurry. The surface of the modified multi-walled carbon nanotubes after being modified with sodium polystyrene sulfonate is functionalized with sulfonic acid and exhibits a negative charge, thus having good dispersibility. In addition, the functionalized graphene also exhibits a negative charge. Under the influence of the charge effect, the composite slurry system can maintain a stable and uniform dispersion system.

[0021] Based on the high strength of modified multi-walled carbon nanotubes (MWCNTs), when used in conjunction with functionalized graphene, the MWCNTs intersperse between the functionalized graphene layers, reducing stacking defects and helping to further improve the coating's hardness and wear resistance. Due to the excellent conductivity of MWCNTs, they can act as "conductors" bridging the functionalized graphene sheets, constructing a "surface + line" dual-network structure to form a more stable conductive pathway, which helps to further suppress electrochemical corrosion. Furthermore, MWCNTs can fill the spaces between metal sheet structures, helping to form a more continuous and compact barrier, effectively reducing the penetration of corrosive media and resulting in better corrosion resistance of the coating.

[0022] In addition, sodium polystyrene sulfonate itself has dispersing and thickening effects, and can be adsorbed on the surface of silicon microparticles through electrostatic stabilization mechanism to form a double electric layer structure, further reducing particle agglomeration. On this basis, silicon microparticles tend to combine with modified multi-walled carbon nanotubes to a certain extent, so that the modified multi-walled carbon nanotubes and silicon microparticles in the coating system tend to fill the spaces between functionalized graphene layers or metal sheet structures, which is conducive to forming a continuous and dense barrier structure, resulting in better coating density and corrosion resistance.

[0023] Meanwhile, the selected β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane both contain epoxy groups, which can bond with the sulfonic acid groups contained in the modified multi-walled carbon nanotubes and the amino groups on the surface of functionalized graphene, forming stable Si-O-Si covalent bonds with silicon micropowder. Therefore, a structurally stable cross-linked network can be formed between functionalized graphene, silicon micropowder and modified multi-walled carbon nanotubes, which helps to improve the structural stability and hardness of the coating, and further improves the density of the coating and the corrosion resistance.

[0024] Preferably, the preparation method of the modified multi-walled carbon nanotubes includes the following steps: adding multi-walled carbon nanotube raw materials and sodium polystyrene sulfonate to deionized water, ultrasonically dispersing and continuing to stir, then heating to 60-80°C for reaction, and after the reaction is completed, proceeding through cooling, ultrasonic dispersion, filtration and vacuum drying steps to obtain modified multi-walled carbon nanotubes.

[0025] Preferably, the zinc powder and aluminum powder are both in flake form, the zinc powder has a particle size of 10-30 μm, the aluminum powder has a particle size of 5-20 μm; the functionalized graphene has a particle size of 20-40 μm; the silicon micropowder has a particle size of 50-200 nm; and the modified multi-walled carbon nanotubes have an outer diameter of 5-30 nm and a length of 1-10 μm.

[0026] By adopting the above technical solution, the particle size range of each raw material is further optimized, so that the particle size of each raw material tends to be gradient distributed, which helps to form a coating with better density.

[0027] Preferably, the preparation method of the composite slurry includes the following steps: mixing functionalized graphene and deionized water to obtain a functionalized graphene aqueous solution; mixing modified multi-walled carbon nanotubes, silicon micropowder, silane coupling agent and deionized water, then adding the functionalized graphene aqueous solution, and mixing and stirring to obtain the composite slurry.

[0028] By adopting the above technical solution, the modified multi-walled carbon nanotubes, silicon powder, silane coupling agent and deionized water are mixed in a preferential manner, so that the silicon powder in the system tends to combine with the modified multi-walled carbon nanotubes and then dispersed into the interlayer of functionalized graphene. While improving the density of the coating structure, it helps to achieve a balance between impedance and conductivity, thereby inhibiting galvanic corrosion and improving the anti-corrosion performance of the coating.

[0029] Secondly, this application provides a method for preparing graphene-modified Dacromet coating, employing the following technical solution: A method for preparing a graphene-modified Dacromet coating includes the following steps: mixing a composite slurry, a film-forming agent, and an additive, dispersing them uniformly, then adding zinc powder, aluminum powder, and deionized water, and dispersing and mixing them to obtain the coating.

[0030] In summary, this application has the following beneficial effects: 1. This application modifies graphene oxide with polyoxyethylene amine and further pre-disperses functionalized graphene and silicon powder with silane coupling agent, overcoming the defect that graphene and silicon powder are prone to agglomeration. This allows graphene and silicon powder to be more stably dispersed in the composite slurry system. Under the combined effect of stable and uniformly dispersed functionalized graphene and silicon powder, a denser and continuous physical barrier is formed, which effectively improves the hardness, wear resistance and density of the coating, giving the coating excellent anti-corrosion performance and comprehensively improving the protective performance of the coating.

[0031] 2. This application constructs conductive pathways in the coating by uniformly dispersing functionalized graphene, making the coating electrochemically inert and achieving zinc-aluminum cathodic protection, which helps to inhibit electrochemical corrosion; the high impedance characteristics of silicon micropowder improve the coating's shielding ability against corrosive media, helping to achieve a balance between impedance and conductivity, thereby effectively inhibiting galvanic corrosion and helping to reduce the problem of poor corrosion protection due to sacrificial anode.

[0032] 3. In this application, it is further preferred that modified multi-walled carbon nanotubes be added to the composite slurry. The modified multi-walled carbon nanotubes with surface sulfonic acid functionalization have good dispersibility and exhibit negative charge. There is a certain charge effect between them and the negatively charged functionalized graphene, which enables the composite slurry system to maintain a stable and uniform dispersion system.

[0033] 4. In this application, modified multi-walled carbon nanotubes are interspersed between functionalized graphene layers, reducing stacking defects and helping to further improve the hardness and wear resistance of the coating. Based on the good conductivity of modified multi-walled carbon nanotubes, they can act as "wires" to bridge functionalized graphene sheets, constructing a "surface + line" dual network structure to form a more stable conductive pathway, which helps to further suppress electrochemical corrosion. Moreover, modified multi-walled carbon nanotubes can fill between metal sheet structures, helping to form a more continuous and compact barrier, effectively reducing the penetration of corrosive media, and resulting in better corrosion resistance of the coating. Detailed Implementation

[0034] In this embodiment, both zinc powder and aluminum powder are in flake form. The particle size of zinc powder is 10–30 μm, the particle size of aluminum powder is 5–20 μm, the particle size of functionalized graphene is 20–40 μm, and the particle size of silicon micropowder is 50–200 nm. The outer diameter of the modified multi-walled carbon nanotubes is 5–30 nm, and the length is 1–10 μm. In this embodiment, the preferred particle size of zinc powder is 25 μm; the preferred particle size of aluminum powder is 10 μm; the preferred particle size of functionalized graphene is 35 μm; the preferred particle size of silicon micropowder is 100 nm, with a purity ≥99%; and the preferred outer diameter of the modified multi-walled carbon nanotubes is 20 nm, with a length of 8 μm. All the particle sizes mentioned above are median particle sizes. The film-forming agent in this embodiment includes at least one of silane coupling agent, silicone resin, molybdate, and manganese acetate. Preferably, the silane coupling agent and molybdate are used as film-forming agents in a mass ratio of 10:1. The silane coupling agent includes at least one of KH-550, KH-560, and KH-570, and the molybdate includes at least one of sodium molybdate, ammonium molybdate, and potassium molybdate. More preferably, KH-570 and potassium molybdate are combined as film-forming agents. In this embodiment, the mass ratio of functionalized graphene, silicon micropowder, silane coupling agent, and deionized water in the composite slurry is 1:(1.2-1.6):(0.1-0.3):(8-10), and a more preferred mass ratio is 1:1.3:0.2:10; in a more preferred embodiment that incorporates modified multi-walled carbon nanotubes, the mass ratio of modified multi-walled carbon nanotubes to functionalized graphene is (0.3-0.6):1, and a more preferred mass ratio is 0.5:1; In this embodiment, the silane coupling agent in the composite slurry is composed of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane in a mass ratio of 1:(1.3-2.5), and more preferably 1:2; wherein the CAS number of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane is 3388-04-3, and the CAS number of γ-glycidoxypropyltrimethoxysilane is 2530-83-8; The polyoxyethyleneamine in this embodiment includes at least one of polyoxyethyleneamine and polyoxypropyleneamine. Polyoxyethylene diamine is preferred in this embodiment for example. The CAS number of polyoxyethylene diamine is 24991-53-5. The additives in this embodiment include polytetrafluoroethylene emulsion and dispersant, with a mass ratio of polytetrafluoroethylene emulsion to dispersant of 1:(4-8), preferably 1:5; wherein the particle size of the polytetrafluoroethylene emulsion is 50-300 nm, more preferably 100 nm; the dispersant includes at least one of sodium polystyrene sulfonate, sodium dodecylbenzene sulfonate, and dodecylphenol polyoxyethylene ether, more preferably sodium polystyrene sulfonate, CAS number 25704-18-1; The present application will be further described in detail below with reference to the embodiments and comparative examples. All raw materials involved in the present application can be obtained commercially.

[0035] Example 1 A graphene-modified Dacromet coating comprises the following raw materials in parts by weight: 270g zinc powder, 80g aluminum powder, 250g composite slurry, 100g film-forming agent, 70g additives, and deionized water to make up to 1000g; the composite slurry includes functionalized graphene, silicon micro powder, silane coupling agent and deionized water, and the functionalized graphene is obtained by modifying graphene oxide with polyoxyethylene diamine. The preparation method of this Dacromet coating includes the following steps: The mass ratio of S1, graphene oxide, and deionized water is 1:10, and the mass ratio of graphene oxide and polyoxyethylene diamine is 1:5. Graphene oxide is added to deionized water and ultrasonically dispersed for 2 hours at a power of 200W to obtain an aqueous solution of graphene oxide. Polyoxyethylene diamine is added to the aqueous solution of graphene oxide and mixed and stirred for 5 hours at a stirring speed of 800 rpm and a stirring temperature of 60℃ to obtain a mixed solution. The mixed solution is centrifuged at 3500 rpm for 10 minutes, the precipitate is discarded, the supernatant is retained, and then vacuum dried at 80℃ for 12 hours to obtain functionalized graphene. S2. Mix and stir the functionalized graphene and deionized water at 600 rpm for 10 min to obtain a functionalized graphene aqueous solution. Mix and stir the silica powder, silane coupling agent, and deionized water at 1000 rpm for 20 min, then add the functionalized graphene aqueous solution and mix and stir for another 30 min to obtain a composite slurry. The mass ratio of functionalized graphene, silica powder, silane coupling agent, and total deionized water is 1:1.3:0.2:10, and the amount of deionized water used in the functionalized graphene aqueous solution accounts for 40 wt% of the total deionized water. S3. Mix the composite slurry, film-forming agent and additives at a stirring speed of 1000 rpm. After dispersing for 10 minutes, add zinc powder, aluminum powder and deionized water. Stir at 600 rpm for 1 hour to obtain the coating.

[0036] The difference between Examples 2-5 and Example 1 lies in the different raw material ratios, as shown in Table 1.

[0037] Table 1 Raw Material Proportioning Table Example 6 The difference between this embodiment and Embodiment 1 is that in step S2, the graphene, silicon micro powder, silane coupling agent and deionized water are mixed and stirred at a speed of 1000 rpm for 1 hour to obtain a composite slurry.

[0038] Example 7 The difference between this embodiment and Embodiment 1 is that the additives do not include polytetrafluoroethylene emulsion.

[0039] Example 8 The difference between this embodiment and Embodiment 1 is that the composite slurry also includes modified multi-walled carbon nanotubes. The modified multi-walled carbon nanotubes are obtained by modifying multi-walled carbon nanotube raw materials with sodium polystyrene sulfonate. The preparation method is as follows: multi-walled carbon nanotube raw materials and sodium polystyrene sulfonate are added to deionized water. The mass ratio of multi-walled carbon nanotube raw materials, sodium polystyrene sulfonate and deionized water is 1:5:12. After ultrasonic dispersion for 30 min, stirring is continued for 10 h at a stirring speed of 500 rpm. Then, the temperature is raised to 80℃ and reacted for 72 h. After the reaction is completed, the modified multi-walled carbon nanotubes are obtained by sequentially cooling, ultrasonic dispersion, filtration and vacuum drying. In step S2, functionalized graphene and deionized water are mixed and stirred at 600 rpm for 10 min to obtain a functionalized graphene aqueous solution. Modified multi-walled carbon nanotubes, silicon powder, silane coupling agent, and deionized water are mixed and stirred at 1000 rpm for 20 min, and then the functionalized graphene aqueous solution is added. After mixing and stirring for another 30 min, a composite slurry is obtained. The mass ratio of modified multi-walled carbon nanotubes, functionalized graphene, silicon powder, silane coupling agent, and total deionized water is 0.5:1:1.3:0.2:10, and the amount of deionized water used in the functionalized graphene aqueous solution accounts for 40 wt% of the total deionized water.

[0040] Example 9 The difference between this embodiment and Embodiment 8 is that the modified multi-walled carbon nanotubes are replaced with an equal amount of multi-walled carbon nanotubes.

[0041] Example 10 The difference between this embodiment and Embodiment 8 is that the modified multi-walled carbon nanotubes are replaced with an equal amount of functionalized graphene.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that an equal amount of graphene oxide is used to replace the functionalized graphene.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that an equal amount of silicon micropowder is used to replace the functionalized graphene.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that an equal amount of functionalized graphene is used to replace the silicon micropowder.

[0045] Comparative Example 4 The difference between this comparative example and Example 1 is that the composite slurry does not include a silane coupling agent and is made up with an equal amount of deionized water.

[0046] Comparative Example 5 The difference between this comparative example and Example 1 is that an equal amount of zinc powder is used to replace the functionalized graphene and silicon powder.

[0047] Performance testing methods Test sample preparation: The metal materials that have undergone surface treatment using existing processes meet the St3 level requirements of ISO8501-1 standard. Dacromet coatings obtained in Examples 1-10 and Comparative Examples 1-5 are used as raw materials. The coatings are applied using an air spraying process at an air pressure of 300 kPa. The surface-treated metal materials are then preheated at 50°C for 15 min, and after surface drying, they are heat-treated at 150-200°C for 30 min to obtain the test samples.

[0048] The test samples were tested according to the following standards: hardness and salt spray corrosion resistance were tested using the test method in GB / T26110-2010; abrasion resistance was tested using the test method in GB / T1768-2006; and adhesion was tested using the test method in GB / T5270-2005. The test results are shown in Table 2.

[0049] Table 2 Performance Test Table Based on the performance test data in Table 2, the Dacromet coating obtained in this application has a hardness of 7H or higher, a wear resistance of more than 160 cycles to the substrate, an adhesion level of 1, and a salt spray corrosion resistance of up to 1500 hours without rust spots, demonstrating excellent overall performance.

[0050] Specifically, considering the test results of Examples 1 and 6, compared to Example 1, the coating of Example 6 showed a significant decrease in salt spray corrosion resistance and abrasion resistance. This may be because the dispersion effect is worsened by directly blending functionalized graphene, silicon powder, silane coupling agent, and deionized water. Meanwhile, the method of premixing silicon powder, silane coupling agent, and deionized water in Example 1 may allow silicon powder to enter the interlayer structure of functionalized graphene and form a structurally stable cross-linked network under the action of silane coupling agent. This has a positive effect on improving the density of the coating, thereby making the coating more abrasion resistant and corrosion resistant.

[0051] Specifically, considering the test results of Examples 1 and 8-10, compared to Example 1, the coating hardness, salt spray corrosion resistance, and wear resistance of Example 8 all showed a significant increase. This may be because the addition of modified multi-walled carbon nanotubes (MWCNTs) has a synergistic effect with functionalized graphene. Specifically, the MWCNTs interspersed between functionalized graphene layers reduce stacking defects, contributing to further improvements in coating hardness and wear resistance. Furthermore, the excellent conductivity of the MWCNTs allows them to bridge functionalized graphene sheets, constructing more stable conductive pathways and further suppressing electrochemical corrosion. Moreover, the MWCNTs can fill the spaces between metal sheet structures, helping to form a more continuous and compact barrier, effectively reducing the penetration of corrosive media and resulting in better corrosion resistance of the coating.

[0052] In Example 9, replacing the modified multi-walled carbon nanotubes with unmodified ones not only failed to achieve the improvement effect of Example 8, but also resulted in a certain degree of decrease in both corrosion resistance and wear resistance compared to Example 1. This may be because the addition of unmodified multi-walled carbon nanotubes to the system caused some agglomeration, which damaged the density of the coating, thus leading to a decrease in the coating's corrosion resistance and wear resistance. In Example 10, compared to Example 1, the properties remained basically unchanged. This indicates that simply adding functionalized graphene with conductivity and high strength cannot significantly optimize the coating performance, and further demonstrates the synergistic effect of functionalized graphene and modified multi-walled carbon nanotubes.

[0053] Specifically, based on the test results of Example 1 and Comparative Examples 1-5, compared with Example 1, the hardness, wear resistance, salt spray corrosion resistance, and adhesion of the coatings in Comparative Examples 1-5 all decreased significantly. This is mainly because the graphene oxide in Comparative Example 1 was not modified and was prone to agglomeration. In Comparative Example 2, no functionalized graphene was added, in Comparative Example 3, no silicon powder was added, and in Comparative Example 5, zinc powder was used to replace functionalized graphene and silicon powder. The performance of the coating was affected by the synergistic effect of functionalized graphene and silicon powder, further confirming the synergistic effect between functionalized graphene and silicon powder.

[0054] In contrast, the composite slurry in Comparative Example 4 did not contain a silane coupling agent, which may have resulted in poor dispersion of the silica powder. Furthermore, the lack of cross-linking effect from the silane coupling agent led to a deterioration in the overall performance of the coating.

[0055] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A graphene-modified Dacromet coating, characterized in that, The raw materials include the following parts by weight: The mixture comprises 20-30 parts zinc powder, 5-10 parts aluminum powder, 15-30 parts composite slurry, 8-15 parts film-forming agent, 1-10 parts additives, and deionized water to bring the total to 100 parts. The composite slurry includes functionalized graphene, silicon micropowder, silane coupling agent, and deionized water. The functionalized graphene is obtained by modifying graphene oxide with polyoxyethylene amine.

2. The graphene-modified Dacromet coating according to claim 1, characterized in that, The preparation method of the functionalized graphene includes the following steps: adding graphene oxide to deionized water and dispersing it ultrasonically to obtain an aqueous solution of graphene oxide; adding polyoxyethylene amine to the aqueous solution of graphene oxide and stirring to obtain a mixed solution; centrifuging the mixed solution, retaining the supernatant, and then vacuum drying to obtain functionalized graphene.

3. The graphene-modified Dacromet coating according to claim 1, characterized in that, The additives include polytetrafluoroethylene emulsion and dispersant, wherein the particle size of the polytetrafluoroethylene emulsion is 50-100 nm.

4. The graphene-modified Dacromet coating according to claim 1, characterized in that, The preparation method of the composite slurry includes the following steps: mixing functionalized graphene and deionized water to obtain a functionalized graphene aqueous solution; mixing silicon micropowder, silane coupling agent and deionized water, then adding the functionalized graphene aqueous solution, and mixing and stirring to obtain the composite slurry.

5. The graphene-modified Dacromet coating according to claim 1, characterized in that, The silane coupling agent is composed of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane in a mass ratio of 1:(1.3-2.5).

6. The graphene-modified Dacromet coating according to claim 5, characterized in that, The composite slurry also includes modified multi-walled carbon nanotubes, which are obtained by modifying multi-walled carbon nanotube raw materials with sodium polystyrene sulfonate.

7. The graphene-modified Dacromet coating according to claim 6, characterized in that, The preparation method of the modified multi-walled carbon nanotubes includes the following steps: adding multi-walled carbon nanotube raw materials and sodium polystyrene sulfonate to deionized water, ultrasonically dispersing and continuing to stir, then heating to 60-80℃ for reaction, and after the reaction is completed, cooling, ultrasonic dispersion, filtration and vacuum drying are performed in sequence to obtain modified multi-walled carbon nanotubes.

8. The graphene-modified Dacromet coating according to claim 6, characterized in that, Both the zinc powder and aluminum powder are in flake form, with the zinc powder having a particle size of 10–30 μm and the aluminum powder having a particle size of 5–20 μm; the functionalized graphene has a particle size of 20–40 μm; the silicon micropowder has a particle size of 50–200 nm; and the modified multi-walled carbon nanotubes have an outer diameter of 5–30 nm and a length of 1–10 μm.

9. The graphene-modified Dacromet coating according to claim 8, characterized in that, The preparation method of the composite slurry includes the following steps: mixing functionalized graphene and deionized water to obtain a functionalized graphene aqueous solution; mixing modified multi-walled carbon nanotubes, silicon micro powder, silane coupling agent and deionized water, then adding the functionalized graphene aqueous solution, and mixing and stirring to obtain the composite slurry.

10. A method for preparing a graphene-modified Dacromet coating as described in any one of claims 1 to 9, characterized in that, Includes the following steps: After mixing the composite slurry, film-forming agent, and additives and dispersing them evenly, zinc powder, aluminum powder, and deionized water are added and dispersed to obtain the coating.

Images