Anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating with double-layer structure as well as preparation method and application of anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating

Abstract

The invention discloses a multifunctional epoxy coating with a double-layer structure, corrosion resistance and ultraviolet aging resistance as well as a preparation method and application thereof, the multifunctional epoxy coating comprises a silane-based sol-gel layer and a nano-composite coating, and the nano-composite coating is positioned above the silane-based sol-gel layer. The preparation process of the silane-based sol-gel layer comprises the step of mixing two or more silane groups according to the mass ratio of (1-30): 1; the preparation process of the nano-composite coating comprises the step of mixing two or more carbon nano-materials according to the hybridization ratio of an easily-dispersed material to a difficultly-dispersed material of (20-1): 1; the preparation method comprises the following steps: mixing the raw materials, synthesizing a nano filler through a hydrothermal method or a solvothermal method, carrying out silane coupling agent modification, adding the nano filler into a coating matrix, and adding 0.05-10wt% of the nano filler into the coating matrix. The silane-based sol-gel layer and the nano-composite coating are sequentially coated on the surface of the pretreated metal substrate, so that the corrosion resistance and the ultraviolet resistance of the epoxy coating are enhanced.

Description

Technical Field

[0001] The invention belongs to the field of epoxy coatings, and relates to a double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, and a preparation method and application thereof. Background Art

[0002] Epoxy resin is a high molecular polymer containing two or more epoxy groups, which forms a thermosetting three-dimensional network structure after reacting with a curing agent. Due to its excellent mechanical properties, chemical stability, corrosion resistance and good thermal properties, epoxy coatings are widely used in industries such as automotive, aerospace, marine and railways. However, internal defects and pores formed in epoxy coatings during the curing process may affect its ability to provide long-term protection in corrosive environments. In addition, interfacial corrosion between the coating and the metal substrate may cause a significant decrease in the adhesion strength of the coating, resulting in peeling of the coating and complete loss of its protective ability.

[0003] Researchers have introduced different nanomaterials into epoxy coatings to enhance their corrosion resistance and adhesion strength, and have exploited the inherent properties of nanomaterials to develop multifunctional properties of coatings. However, another way to improve the adhesion of organic coatings to metal surfaces and improve corrosion resistance is to use environmentally friendly silane-based coating technology by chemically pretreating the substrate surface. Silanes are a class of hybrid molecules with hydrolyzable alcohol groups (such as ethoxy or methoxy) that form hydrophilic silanol groups (Si-OH) under hydrolysis. These silanol groups bind to metal hydroxyl groups (Me-OH) on the substrate through hydrogen bonds. During the curing process, the cohesion of the metal / coating interface forms strong metal-silicon oxygen bonds (Me-O-Si), which enhances adhesion. The additional Si-OH groups in the structure form silicon oxygen chains (Si-O-Si), which effectively protect the metal from the effects of aggressive substances.

[0004] However, in practical applications such as aviation, solar photovoltaic cells, offshore oil and gas production and outdoor storage tanks, it is critical to consider the UV aging of epoxy resins during use. This aging manifests itself as yellowing of the surface, loss of gloss, increased cracking, increased corrosion and a decrease in overall mechanical properties, which affects its service life. Under the action of light, the polymer transforms into an excited state and then decomposes into free radicals, which react with oxygen to form hydrogen peroxide, which ultimately triggers a series of molecular chain cleavage or cross-linking reactions. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating and its preparation method and application, thereby enhancing the durability and long-term performance of the epoxy coating in outdoor applications.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating comprises a silane-based sol-gel layer and a nano-composite coating, wherein the nano-composite coating is located above the silane-based sol-gel layer.

[0007] Preferably, the silane-based sol-gel layer is a mixture of two or more of tetraethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane and 3-glycidyloxypropyltrimethoxysilane, and the mixing ratio is (1-30):1.

[0008] Preferably, the nanocomposite coating is a mixture of two or more of graphene, graphene oxide, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black and carbon nanofibers, and the hybridization ratio of the easily dispersible material to the non-dispersible material is (20~1):1.

[0009] A method for preparing the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, the preparation process of the silane-based sol-gel layer is: two or more silane-based materials are mixed in a mass ratio of (1-30):1: The preparation process of the nanocomposite coating is as follows: two or more carbon nanomaterials are mixed in a hybrid ratio of (20~1):1 between the easily dispersible material and the non-dispersible material, and after mixing, nanofillers are synthesized by a hydrothermal method or a solvothermal method, and the nanofillers are added to the coating matrix, and the amount of the nanofillers added accounts for 0.05~10 wt.% of the coating matrix.

[0010] Preferably, before the nanofiller is added to the coating matrix, the nanofiller is modified by a silane coupling agent to obtain a modified nanofiller.

[0011] Preferably, when the nanofiller is synthesized by a hydrothermal method, the heat treatment is carried out in deionized water at 80-200° C. for 4-24 h; when the nanofiller is synthesized by a solvothermal method, the heat treatment is carried out in a mixture of deionized water and an organic solvent at 60-120° C. for 10-24 h, and the organic solvent is ethanol or acetone.

[0012] Preferably, the coating matrix is ​​epoxy resin.

[0013] Preferably, the nanofiller is diluted with a solvent to form a thin solution or paste in the form of a thin stream of water, which is then evenly dispersed and added to the coating matrix, and finally the curing agent is added.

[0014] An application of the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating is to coat the silane-based sol-gel layer and the nano-composite coating in sequence on the surface of a pretreated metal substrate.

[0015] Preferably, the coating thickness of the nanocomposite coating is 1 to 1000 μm.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention aims to design a double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, which combines multifunctional characteristics, has both anti-corrosion and anti-ultraviolet performance, and has excellent mechanical properties, so as to solve the limitations of epoxy coatings in long-term outdoor use. The silane-based sol-gel layer is used to enhance the adhesion of the coating, and the nano-composite epoxy coating containing silane-modified carbon-based nano-hybrid materials is used as a surface protective layer. The sol-gel layer uses different silane-based solutions for composite hydrolysis, which can form a denser and more continuous sol-gel layer than the traditional single silane agent; and the modified nano-hybrid material in the epoxy layer combines multiple carbon-based materials in a strong covalent form, combining the advantages of all nano-materials in the same coating system while abandoning their disadvantages. This design provides an innovative solution for protective coatings in the industrial and construction fields, introduces new ideas from the perspectives of structure and materials, and enhances the durability of epoxy coatings in outdoor applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Transmission electron microscopy images of graphene oxide and carbon nanotube hybrid materials (ab) GO@CNTs and (c) F-GO@CNTs after hybrid modification.

[0018] Figure 2 This is a visual observation comparison chart of the coating surface of pure epoxy coating and double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating during the salt spray test for 1-60 days; Figure 3 It is a comparison chart of the changing trends of the electrochemical impedance values ​​of the pure epoxy coating and the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating before and after UV irradiation; Figure 4 It is a comparison chart of the degree of surface coating damage of epoxy coating and double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating before and after UV irradiation; Figure 5 This is a comparison chart of the surface scanning electron microscope observation of epoxy coating and double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating before and after ultraviolet radiation. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0020] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0021] The present invention designs a double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating (Ep / F-GO@CNTs), which solves the problem that epoxy coating cannot provide long-term protection outdoors.

[0022] The first layer is a continuous and dense silane-based sol-gel layer after chemical pretreatment of the metal substrate surface to improve the adhesion strength and anti-corrosion performance of the coating. The silane-based sol-gel layer can be a mixture of two or more of tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), methyltriethoxysilane (MTES) and 3-glycidyloxypropyltrimethoxysilane (GPTMS), etc., with a mixing mass ratio of (1-30):1, preferably in the range of (3-20):1, and optimally in the range of (5-10):1.

[0023] The other layer is a nanocomposite coating, which is located above the silane-based sol-gel layer. The silane-based sol-gel layer serves as an intermediate reinforcement layer between the nanocomposite coating and the metal substrate. The nanocomposite coating uses a variety of carbon nanomaterials, which can be two or more of graphene, graphene oxide, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black and carbon nanofibers. The hybridization ratio of the easily dispersible material to the non-dispersible material is (20~1):1, the better range is (10~1):1, and the best range is (5~2):1.

[0024] The present invention also provides a method for preparing a nano composite coating, wherein different carbon nano materials are mixed by ultrasonic and magnetic stirring, and after mixing, nano fillers are synthesized by a hydrothermal method or a solvent thermal method.

[0025] Furthermore, the nanofillers can be modified by silane coupling agents to obtain corrosion-resistant and UV-resistant nanofillers. The modified nanofillers can be evenly dispersed in the polymer matrix and interact with groups such as hydroxyl and epoxy groups in the matrix to form a continuous polysiloxane network in the coating matrix, which enhances the interface stability, mechanical strength and environmental durability, ensuring improved long-term performance.

[0026] Wherein, when the nanofiller is synthesized by the hydrothermal method, specifically: heat treatment is performed in deionized water at 80-200°C for 4-24 h; preferably heat treatment is performed at 100-180°C for 6-18 h; more preferably heat treatment is performed at 120-160°C for 8-16 h.

[0027] When the nanofiller is synthesized by the solvothermal method, specifically: heat treatment is performed at 60 to 120° C. for 10 to 24 h in a mixture of deionized water and an organic solvent, and the organic solvent is ethanol or acetone.

[0028] The nanofiller is added to the coating matrix, the coating matrix uses epoxy resin, the water-based polymer uses water as a solvent and diluent, and the preparation process of the solvent-based polymer uses an organic solvent (one of n-hexane, toluene, xylene, methyl ethyl ketone, ethanol, isopropanol, tert-butyl alcohol, n-butyl acetate and other solvents or a mixture thereof). When adding the nanofiller, the nanofiller is diluted with a solvent to form a thin stream of water-like dilute solution or paste, and then one or more of a high shear mixer, a mechanical mixer, and a probe ultrasound are used to uniformly disperse and add it to the polymer resin to prevent the nano hybrid from agglomerating and precipitating in the polymer matrix, and finally a curing agent is added.

[0029] The amount of the nanofiller added is 0.05 to 10 wt.% of the coating matrix; preferably 0.05 to 8 wt.%; and more preferably 0.1 to 5 wt.%.

[0030] The present invention also provides an application of a nanocomposite coating, wherein a coating with added nanofillers is directly coated on a substrate coated with a silane-based sol-gel layer, and is formed on the surface of a metal structure by brushing, spraying, dipping or spin coating, with a coating thickness of 1 to 1000 µm; preferably 10 to 500 µm; and more preferably 100 to 300 µm.

[0031] Example 1 Q235 steel plate was used as the substrate for coating and cleaned with acetone and anhydrous ethanol. The cleaned steel substrate was activated in an alkaline solution of 25 g / L sodium hydroxide at 55 °C for 7 min to form -OH groups on the steel substrate.

[0032] To prepare a silane-based sol-gel layer, MTES and TEOS were mixed in a volume ratio of 1:1. In order to accelerate the hydrolysis reaction of silane, the pH value of the solution was adjusted to 3 using acetic acid. Subsequently, the solution was sealed and mixed at room temperature for 24 h. After the steel sample was immersed in the silane-based sol-gel layer for 60 s, it was taken out at a speed of 0.3 m / min, and the coated sample was allowed to stand at room temperature for 40 min. Subsequently, it was heated at 85°C for 2 h. That is, the silane-based sol-gel layer of the double-layer coating system was prepared and cooled to room temperature for use.

[0033] 40 mL of 10 mg / mL graphene oxide (GO) solution and 30 mL of ethanol were mixed and stirred for 60 min. Then, 0.1 g of hydroxylated carbon nanotubes (CNTs-OH) were added to the mixture and subjected to ultrasonic bath treatment for 30 min. After that, the mixture was reacted with magnetic stirring at room temperature for 5 h. The obtained mixture was poured into a 100 mL Teflon-lined autoclave and heat treated at 120 °C for 10 h. Finally, when the temperature of the autoclave dropped to room temperature, the autoclave was opened, the solution was centrifuged and washed with water and ethanol several times, and the obtained precipitate (i.e., the synthesized GO@CNTs) was dried in an oven at 60 °C ( Figure 1 ab).

[0034] 5 mL of APTES was mixed with 95 mL of deionized water and stirred for 30 min using a magnetic stirrer. During the stirring process, 0.5 g of nanomaterials was added. Then, stirring was continued for 20 min using a magnetic stirrer and then treated with an ultrasonic bath homogenizer for 10 min. The suspension was kept in a reflux state at 70 °C and stirred for 8 h. In order to remove the remaining silane compounds attached to the nanomaterials, the final suspension was centrifuged and washed twice with water. Finally, the product (i.e., synthesized F-GO@CNTs) was dispersed in deionized water to obtain the modified nanofiller ( Figure 1 c).

[0035] A solution of 0.1 wt.% of the modified nanofiller in 10 mL of deionized water was prepared, stirred for 20 min, and then sonicated for 10 min. The resulting solution was then added to 100 g of waterborne epoxy resin and stirred until a uniform mixture was obtained, followed by further sonication for 10 min. Subsequently, 50 g of hardener was added to the mixture, which was then debubbled and coated on a metal substrate. Finally, the coating was allowed to dry at room temperature for 7 days and then dried in an oven at 80 °C for 4 h. That is, a nanocomposite epoxy layer of a double-layer coating system was obtained.

[0036] For the above-mentioned double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, the corrosion resistance of pure epoxy coating and double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating before and after ultraviolet exposure was evaluated by electrochemical impedance spectroscopy and salt spray tests. Figure 2 and 3 Specifically: According to ASTM B117 standard, the anti-corrosion performance of the coating was visually monitored by salt spray test. The sample surface was scratched with a utility knife to damage the metal substrate, and a 12-hour spray of 5% sodium chloride salt spray and 12-hour drying were performed for 60 days, and the corrosion products on the sample surface were observed. Figure 2,It can be seen that the pure epoxy coating experienced bubbling and a large amount of corrosion products seeping out after 30 days, while the nanocomposite coating only had a small amount of corrosion products at the scratches.

[0037] The corrosion resistance of pure epoxy coating and double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating was evaluated by electrochemical workstation PARSTAT 4000+. A three-electrode system was used, including an auxiliary electrode (4 cm 2 Platinum sheet), working electrode (coated steel plate) and reference electrode (saturated calomel electrode, SCE) were tested in 3.5 wt.% sodium chloride solution. Before the experiment, the sample was tested for open circuit potential in the corrosive medium, and the open circuit potential change was recorded. After the open circuit potential stabilized, the electrochemical impedance spectroscopy test was performed, and the test frequency range was set to 10 5 Hz~0.01 Hz, and the amplitude of the AC sinusoidal disturbance signal is 20 mV.

[0038] Figure 3 The electrochemical impedance spectroscopy results are shown in Figure 2 after immersion in 3.5 wt.% NaCl solution for 40 days. The electrochemical impedance values ​​show that before UV irradiation, the impedance modulus of the double-layer anti-corrosion and UV-resistant multifunctional epoxy coating is significantly higher than that of the pure epoxy sample. At a low frequency of 0.01 Hz, the impedance value of the double-layer anti-corrosion and UV-resistant multifunctional epoxy coating and the pure epoxy coating is 7.6×10 9 Ω.cm 2 and 4.7×10 8 Ω.cm 2 , which is an order of magnitude higher than that of the pure epoxy coating. The impedance values ​​of the double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating and the pure epoxy coating were 5.3×10 8 Ω.cm 2 and 1.1×10 5 Ω.cm 2 It can be seen that the pure epoxy coating has lost its anti-corrosion performance, while the double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating has a relatively excellent resistance to UV aging.

[0039] In order to evaluate the anti-ultraviolet aging ability of the composite coating and understand the corresponding internal mechanism, a UV accelerated aging tester was used to simulate the irradiation aging process of the coating samples, such as Figure 4 Specifically: According to ISO 16474–2021, UVB lamps (20 × 3 W) with a wavelength range of 313 nm were used. During the UV radiation test, the alternating process of irradiation (8 h) and darkness (4 h) was considered as a cycle, and the cumulative irradiation time was 240 h. After the simulation experiment, the corrosion resistance was investigated using the same measurement conditions as above. The effect of UV radiation on the coating structure was observed by an optical camera.

[0040] Figure 4 The surface state changes of pure epoxy coating and double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating after UV exposure. The PE sample showed a significant color change from white to yellow, which was attributed to the ring-opening reaction of the benzene-containing material triggered by UV damage, while the color of the Ep / F-GO@CNTs sample remained relatively stable. Subsequently, SEM analysis of the surfaces of PE and Ep / F-GO@CNTs samples showed that defects and pores appeared on the PE surface before UV irradiation, probably due to the volatilization of solvents during the curing process. In contrast, the surface of Ep / F-GO@CNTs was relatively smooth, with significantly fewer defects and pores. Under UV irradiation, extensive deep cracks appeared on the PE surface, forming a mesh pattern on the surface of the PE coating, with most of the cracks coming from existing pores and pits ( Figure 5 ), which provides a path for the penetration of corrosive ions. Although cracks also appeared on the surface of Ep / F-GO@CNTs, they were shorter and shallower, indicating that the modified hybrid material has an enhanced ability to resist UV-induced degradation.

[0041] Example 2 Q235 steel plate was used as the substrate for coating and cleaned with acetone and anhydrous ethanol. The cleaned steel substrate was activated in an alkaline solution of 25 g / L sodium hydroxide at 55 °C for 7 min to form OH groups on the steel substrate.

[0042] For the silane-based sol-gel layer, a mixture of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTS) was used to enhance the corrosion resistance of the steel substrate. The mass ratio of TEOS / APTS was 70:30, so that a more continuous and dense coating could be formed, which had better anti-corrosion performance than a single silane. The silane-based sol-gel layer was prepared by dip coating and placed in an oven at 80 °C for 2 h for use.

[0043] 500 mg of carbon black and HNO3 / H2SO4 (1:3, v / v) mixture were stirred, both with a concentration of 5 molar, and refluxed at 100 ° C for 3 h to obtain modified carbon black. 30 mL of GO solution (concentration of 10 mg / mL) and 30 mL of ethanol were mixed and stirred for 60 min. Then, 0.3 g of modified carbon black was added to the mixture and ultrasonic bath treated for 30 min. After that, the reaction was magnetically stirred at room temperature for 5 h. The obtained mixture was poured into a 100 mL Teflon-lined autoclave and heat treated at 120 ° C for 12 h. Finally, when the temperature of the autoclave dropped to room temperature, the autoclave was opened, the solution was centrifuged and washed with water and ethanol several times, and the obtained precipitate (i.e., the synthesized GO@CB) was dried in an oven at 60 ° C.

[0044] 5 mL of APTES was mixed with 95 mL of deionized water and stirred for 120 min using a magnetic stirrer. During the stirring process, 0.5 g of GO@CB nanohybrid material was added. Then the stirring was continued for 60 min using a magnetic stirrer and then treated with an ultrasonic bath homogenizer for 10 min. The suspension was kept in a reflux state at 100 °C and stirred for 12 h. In order to remove the remaining silane compounds attached to the nanomaterial, the suspension was centrifuged and washed with water twice. Finally, the product (i.e., the synthesized F-GO@CB) was dried in an oven at 80 °C to obtain the modified nanofiller.

[0045] A solution of 75 mg of modified nanofiller was dissolved in 10 mL of deionized water, stirred for 60 min, then sonicated for 60 min, and then the resulting solution was added to 100 g of epoxy resin and stirred until a uniform mixture was obtained, followed by further sonication for 10 min. Subsequently, 50 g of hardener was added to the mixture, which was then de-bubbled and applied to the metal substrate to prepare a successful composite epoxy layer. Finally, the coating was allowed to dry at room temperature for 7 days, and then dried in an oven at 80 °C for 4 h to obtain a complete double-layer structure coating.

[0046] For the above-mentioned double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, the corrosion resistance of pure epoxy coating and double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating was evaluated by electrochemical impedance and salt spray tests. After the coating was exposed to strong UV outdoors for 3 months, the UV resistance of the surface coating was observed again and electrochemical evaluation was performed. The results show that the prepared double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating has better anti-ultraviolet aging and anti-corrosion properties than pure epoxy coating, and the addition of nanofillers and the design of the double-layer structure significantly increase the adhesion strength of the coating.

[0047] Example 3 The substrate is AA2024-T3 aluminum alloy, and the sample is etched in 50 g / L sodium hydroxide solution for 30 s and in 400 g / L nitric acid solution for 30 s at room temperature. Finally, the substrate surface is rinsed with deionized water and blown dry in air.

[0048] For the silane-based sol-gel layer, a mixture of methyltriethoxysilane (MTES) and 3-glycidyloxypropyltrimethoxysilane (GPTMS) was used, and the mass ratio of MTES / GPTMS was 30: 1. The silane-based sol-gel layer was prepared by dip coating and was placed in an oven at 80°C for 2 h before use.

[0049] 500 mg of carbon nanohorn (CH) and HNO3 / H2SO4 (1:3, v / v) mixture were stirred, both with a concentration of 5 molar, and refluxed at 100 ° C for 3 h to obtain modified carbon nanohorns. 30 mL of GO solution (concentration of 10 mg / mL) and 30 mL of ethanol were mixed and stirred for 60 min. Then, 0.015 g of modified carbon nanohorn was added to the mixture and ultrasonic bath treated for 60 min. After that, the reaction was magnetically stirred at room temperature for 5 h. The obtained mixture was poured into a 100 mL Teflon-lined autoclave and heat treated at 60 ° C for 24 h. Finally, when the temperature of the autoclave dropped to room temperature, the autoclave was opened, the solution was centrifuged and washed with water and ethanol several times. The precipitate (i.e., the synthesized GO@CH) was dried in an oven at 60 ° C to obtain a nanofiller.

[0050] A solution of 15 g of nanofiller was dissolved in 30 mL of deionized water, stirred for 120 min, and then ultrasonicated for 60 min. The resulting solution was then added to 100 g of epoxy resin and stirred until a uniform mixture was obtained, followed by further probe ultrasonication for 10 min. Subsequently, 50 g of hardener was added to the mixture and stirred evenly, and then coated on the reserved silane-based sol-gel layer to successfully prepare a double-layer structure corrosion-resistant and UV-resistant aging coating. Finally, the coating was allowed to dry at room temperature for 7 days, and then dried in an oven at 80 ° C for 4 h to obtain a complete coating.

[0051] The corrosion resistance of the pure epoxy coating and the double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating was evaluated by electrochemical testing, salt spray assessment, corrosion product analysis, etc. After the coating was exposed to strong UV light outdoors for 3 months, the UV resistance of the surface coating was observed again and an electrochemical evaluation was performed. The results show that the prepared double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating has better anti-ultraviolet aging and anti-corrosion properties than pure epoxy coating, and the addition of nanofillers and the design of the double-layer structure significantly increase the surface hydrophobicity and mechanical properties of the coating.

[0052] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0053] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0054] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0055] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0056] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

[0057] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of such subject matter, nor should it be considered that the applicant has not considered such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating, characterized in that: The invention comprises a silane-based sol-gel layer and a nano-composite coating, wherein the nano-composite coating is located on the silane-based sol-gel layer.

2. The double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 1 is characterized in that: The silane-based sol-gel layer is a mixture of two or more of tetraethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane and 3-glycidyloxypropyltrimethoxysilane, and the mixing ratio is (1~30):

1.

3. The double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 1 is characterized in that: The nanocomposite coating is a mixture of two or more of graphene, graphene oxide, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black and carbon nanofibers, and the hybridization ratio of the easily dispersible material to the non-dispersible material is (20~1):

1.

4. A method for preparing a double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to any one of claims 1 to 3, characterized in that: The preparation process of the silane-based sol-gel layer is as follows: two or more silane-based groups are mixed in a mass ratio of (1-30):1: The preparation process of the nanocomposite coating is as follows: two or more carbon nanomaterials are mixed in a hybrid ratio of (20~1):1 between the easily dispersible material and the non-dispersible material, and then the nanofiller is synthesized by a hydrothermal method or a solvothermal method, and then the nanofiller is added to the coating matrix, and the amount of the nanofiller added accounts for 0.05~10 wt.% of the coating matrix.

5. The method for preparing the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 4, characterized in that: Before the nanofiller is added into the coating matrix, the nanofiller is modified by a silane coupling agent to obtain the modified nanofiller.

6. The method for preparing the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 4, characterized in that: When the nanofiller is synthesized by the hydrothermal method, it is heat treated at 80-200°C in deionized water for 4-24 h. When the nanofiller is synthesized by the solvothermal method, it is heat treated at 60-120°C in a mixture of deionized water and an organic solvent for 10-24 h, and the organic solvent is ethanol or acetone.

7. The method for preparing the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 4, characterized in that: The coating matrix is ​​epoxy resin.

8. The method for preparing the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 4, characterized in that: The nanofiller is diluted with a solvent to form a thin solution or paste in the form of a thin stream of water, which is then evenly dispersed and added to the coating matrix, and finally a curing agent is added.

9. An application of the double-layer anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to any one of claims 1 to 3, characterized in that: The silane-based sol-gel layer and the nano-composite coating are sequentially coated on the pretreated surface of the metal substrate.

10. The use of the double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating according to claim 9, characterized in that: The coating thickness of the nanocomposite coating is 1 to 1000 µm.

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