A double-layer structure anticorrosion and ultraviolet aging resistant multifunctional epoxy coating, a preparation method and application thereof

Abstract

The application discloses a kind of double-layer structure anticorrosion and ultraviolet aging prevention multifunctional epoxy coating and its preparation method and application, including silane-based sol-gel layer and nano composite coating, and nano composite coating is located above silane-based sol-gel layer.The preparation process of silane-based sol-gel layer is: two or more silane-based are mixed with mass ratio (1~30):1;The preparation process of nano composite coating is: two or more carbon nanomaterials are mixed with the hybridization ratio of easy dispersion material and not easy dispersion material (20~1):1, after mixing, nano filler is synthesized by hydrothermal method or solvothermal method, and then modified by silane coupling agent, then nano filler is added to coating matrix, and the amount of nano filler is 0.05~10 wt.% of coating matrix.Silane-based sol-gel layer and nano composite coating are coated on the surface of pretreated metal substrate in sequence, and the corrosion resistance and ultraviolet resistance of epoxy coating are enhanced.

Description

Technical Field

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

[0002] Epoxy resin is a high-molecular-weight polymer containing two or more epoxy groups, which react with a curing agent to form a thermosetting three-dimensional network structure. 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 railway. However, internal defects and porosity formed in the epoxy coating during the curing process can affect its ability to provide long-term protection in corrosive environments. Furthermore, interfacial corrosion between the coating and the metal substrate can significantly reduce the coating's adhesion strength, leading to coating peeling and complete loss of protective capability.

[0003] Researchers have introduced various nanomaterials into epoxy coatings to enhance their corrosion resistance and adhesion strength, and have utilized the inherent properties of nanomaterials to develop multifunctional coating properties. However, another approach to improving the adhesion of organic coatings to metal surfaces and enhancing corrosion resistance is through chemical pretreatment of the substrate surface using environmentally friendly silane coating technology. Silanes are hybrid molecules with hydrolyzable alcohol groups (such as ethoxy or methoxy groups), which, upon hydrolysis, form hydrophilic silanol groups (Si-OH). These silanol groups bind to metal hydroxyl groups (Me-OH) on the substrate via hydrogen bonds. During curing, the cohesion at the metal / coating interface forms strong metal-siloxane bonds (Me-O-Si), enhancing adhesion. Additional Si-OH groups in the structure form siloxane chains (Si-O-Si), effectively protecting the metal from corrosive substances.

[0004] However, in practical applications such as aviation, solar photovoltaic cells, offshore oil and gas extraction, and outdoor storage tanks, it is crucial to consider the UV aging of epoxy resins during use. This aging manifests as surface yellowing, loss of gloss, increased cracking, accelerated corrosion, and a decline in overall mechanical properties, thus affecting its service life. Under light exposure, the polymer transforms into an excited state and then decomposes into free radicals. These free radicals react with oxygen to generate hydrogen peroxide, ultimately triggering a series of molecular chain cleavage or cross-linking reactions. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating, its preparation method and application, which enhances the durability and long-term performance of epoxy coatings in outdoor applications.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A dual-layer anti-corrosion and anti-UV aging multifunctional epoxy coating includes a silane sol-gel layer and a nanocomposite coating, with the nanocomposite coating located above the silane sol-gel layer.

[0008] Preferably, the silane sol-gel layer is a mixture of two or more of tetraethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane and 3-glycidyloxypropyltrimethoxysilane, in a mixing ratio of (1~30):1.

[0009] 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, with a hybridization ratio of easily dispersible materials to difficult-to-dispersible materials of (20~1):1.

[0010] A method for preparing the aforementioned dual-layer anti-corrosion and anti-UV aging multifunctional epoxy coating, wherein the preparation process of the silane sol-gel layer is as follows: mixing two or more silane groups in a mass ratio of (1~30):1.

[0011] The preparation process of the nanocomposite coating is as follows: two or more carbon nanomaterials are mixed in a hybrid ratio of easily dispersible material to non-dispersible material of (20~1):1. After mixing, nanofillers are synthesized by hydrothermal or solvothermal methods. The nanofillers are added to the coating matrix, and the amount of nanofillers added accounts for 0.05~10 wt. of the coating matrix.

[0012] Preferably, before adding the nanofiller to the coating matrix, the nanofiller is modified by a silane coupling agent to obtain the modified nanofiller.

[0013] Preferably, when synthesizing nanofillers using the hydrothermal method, the nanofillers are heat-treated in deionized water at 80–200°C for 4–24 h; when synthesizing nanofillers using the solvothermal method, the nanofillers are heat-treated in a mixture of deionized water and an organic solvent at 60–120°C for 10–24 h, wherein the organic solvent is ethanol or acetone.

[0014] Preferably, the coating matrix is ​​made of epoxy resin.

[0015] Preferably, the nanofiller is diluted with a solvent to form a thin, watery solution or paste, then uniformly dispersed and added to the coating matrix, and finally a curing agent is added.

[0016] An application of the aforementioned dual-layer anti-corrosion and anti-UV aging multifunctional epoxy coating involves sequentially coating a silane sol-gel layer and a nanocomposite coating onto the surface of a pretreated metal substrate.

[0017] Preferably, the coating thickness of the nanocomposite coating is 1 to 1000 µm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention aims to design a dual-layer, multifunctional epoxy coating that combines corrosion resistance and UV aging protection. It integrates multiple properties, offering both corrosion resistance and UV protection, along with excellent mechanical properties, to overcome the limitations of epoxy coatings in long-term outdoor use. A silane-based sol-gel layer enhances coating adhesion, while a nanocomposite epoxy coating containing silane-modified carbon-based nano-hybrid materials serves as a surface protective layer. The sol-gel layer utilizes composite hydrolysis of different silane solutions, resulting in a denser and more continuous sol-gel layer compared to traditional single silane agents. The modified nano-hybrid materials in the epoxy layer combine multiple carbon-based materials in a strongly covalent manner, integrating the advantages of all nanomaterials within a single coating system while eliminating their disadvantages. This design provides an innovative solution for protective coatings in industrial and construction fields, introducing new ideas from both structural and material perspectives, and enhancing the durability of epoxy coatings in outdoor applications. Attached Figure Description

[0020] Figure 1 These are transmission electron microscopy (TEM) images of graphene oxide and carbon nanotube hybrid materials (ab) GO@CNTs and hybridized (c) F-GO@CNTs.

[0021] Figure 2 These are visual comparison images of the coating surfaces of pure epoxy coating and double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating during salt spray tests from 1 to 60 days.

[0022] Figure 3 This is a comparison chart showing the changes in electrochemical impedance values ​​of pure epoxy coating and double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating before and after UV irradiation.

[0023] Figure 4 This is a comparison chart showing the degree of surface coating damage before and after ultraviolet irradiation of epoxy coating and double-layer structure anti-corrosion and anti-ultraviolet aging multifunctional epoxy coating.

[0024] Figure 5 These are comparison images of the epoxy coating and the double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating before and after UV radiation observation using scanning electron microscopy. Detailed Implementation

[0025] 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 denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0027] This invention designs a double-layer structure anti-corrosion and anti-UV aging multifunctional epoxy coating (Ep / F-GO@CNTs), which solves the problem that epoxy coatings cannot provide long-term protection outdoors.

[0028] The first layer is a continuous and dense silane sol-gel layer formed by chemical pretreatment of the metal substrate surface to improve the adhesion strength and corrosion resistance of the coating. The silane sol-gel layer can be a mixture of two or more of tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), methyltriethoxysilane (MTES), and 3-glycidyloxypropyltrimethoxysilane (GPTMS), with a mixing mass ratio of (1~30):1, preferably in the range of (3~20):1, and optimal in the range of (5~10):1.

[0029] The other layer is a nanocomposite coating, located above the silane sol-gel layer, which serves as an intermediate reinforcing layer between the nanocomposite coating and the metal substrate. The nanocomposite coating utilizes various carbon nanomaterials, including two or more from graphene, graphene oxide, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black, and carbon nanofibers. The hybridization ratio of easily dispersible to poorly dispersible materials is (20~1):1, with a more favorable range of (10~1):1 and an optimal range of (5~2):1.

[0030] The present invention also provides a method for preparing a nanocomposite coating, wherein different carbon nanomaterials are mixed by ultrasonic and magnetic stirring, and then nanofillers are synthesized by hydrothermal or solvothermal methods.

[0031] Furthermore, nanofillers can be modified with silane coupling agents to obtain corrosion-resistant and UV-resistant nanofillers. The modified nanofillers can be uniformly dispersed in the polymer matrix and interact with hydroxyl and epoxy groups in the matrix to form a continuous polysiloxane network in the coating matrix. This network enhances interfacial stability, mechanical strength, and environmental durability, ensuring improved long-term performance.

[0032] Specifically, when synthesizing nanofillers using a hydrothermal method, the process involves heat treatment in deionized water at 80–200°C for 4–24 h; preferably at 100–180°C for 6–18 h; and even more preferably at 120–160°C for 8–16 h.

[0033] When synthesizing nanofillers using the solvothermal method, the process involves heat treatment at 60–120°C for 10–24 h in a mixture of deionized water and an organic solvent, where the organic solvent is ethanol or acetone.

[0034] Nanofillers are added to the coating matrix, which is an epoxy resin. For waterborne polymers, water is used as both a solvent and diluent, while for solvent-based polymers, organic solvents (such as n-hexane, toluene, xylene, methyl ethyl ketone, ethanol, isopropanol, tert-butanol, n-butyl acetate, and other solvents or mixtures thereof) are used in the preparation process. When adding nanofillers, they are diluted with a solvent to form a thin, watery solution or paste. Then, they are uniformly dispersed into the polymer resin using one or more of the following methods: high-shear mixer, mechanical mixer, and ultrasonic probe. This prevents the nanocomposites from agglomerating and precipitating in the polymer matrix. Finally, a curing agent is added.

[0035] The amount of nanofiller added accounts for 0.05 to 10 wt.% of the coating matrix; preferably 0.05 to 8 wt.%; more preferably 0.1 to 5 wt.%.

[0036] This invention also provides the application of nanocomposite coatings, in which a coating with added nanofillers is directly applied to a substrate already coated with a silane sol-gel layer, and a uniform coating 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.

[0037] Example 1

[0038] Q235 steel plate was used as the substrate for the coating and was 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.

[0039] To prepare the silane sol-gel layer, MTES and TEOS were mixed at a volume ratio of 1:1. To accelerate the hydrolysis of silane, the pH of the solution was adjusted to 3 using acetic acid. The solution was then sealed and mixed at room temperature for 24 h. A steel sample was immersed in the silane sol-gel layer for 60 s and then removed at a speed of 0.3 m / min. The coated sample was then allowed to stand at room temperature for 40 min. Subsequently, it was heated at 85 °C for 2 h. Thus, the silane sol-gel layer of the two-layer coating system was prepared and cooled to room temperature for later use.

[0040] 40 mL of a 10 mg / mL graphene oxide (GO) solution was mixed with 30 mL of ethanol and stirred for 60 min. Then, 0.1 g of hydroxylated carbon nanotubes (CNTs-OH) were added to the mixture and ultrasonically treated for 30 min. Afterward, the reaction was magnetically stirred at room temperature for 5 h. The resulting mixture was poured into a 100 mL Teflon-lined autoclave and heat-treated at 120 °C for 10 h. Finally, when the autoclave temperature cooled to room temperature, the autoclave was opened, the solution was centrifuged, and washed repeatedly with water and ethanol. The resulting precipitate (i.e., the synthesized GO@CNTs) was dried in an oven at 60 °C. Figure 1 ab).

[0041] 5 mL of APTES was mixed with 95 mL of deionized water and stirred with a magnetic stirrer for 30 min. During stirring, 0.5 g of nanomaterials was added. Stirring was continued for another 20 min, followed by ultrasonic homogenization for 10 min. The suspension was refluxed at 70 °C and stirred continuously for 8 h. To remove residual silane compounds adhering to the nanomaterials, the final suspension was centrifuged and washed twice with water. Finally, the product (i.e., the synthesized F-GO@CNTs) was dispersed in deionized water to obtain the modified nanofiller (…). Figure 1 c).

[0042] A solution of 0.1 wt.% modified nanofiller was prepared in 10 mL of deionized water, stirred for 20 min, and then sonicated for 10 min. The resulting solution was then added to 100 g of aqueous epoxy resin and stirred until a homogeneous mixture was obtained, followed by further sonication for 10 min. Subsequently, 50 g of hardener was added to the mixture, and the mixture was degassed and coated onto 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. This yielded a nanocomposite epoxy layer with a two-layer coating system.

[0043] The corrosion resistance of the aforementioned dual-layer anti-corrosion and UV-aging-resistant multifunctional epoxy coating before and after UV exposure was evaluated using electrochemical impedance spectroscopy and salt spray tests. Figure 2 and 3 As shown. Specifically:

[0044] According to ASTM B117 standard, the corrosion resistance of the coating was visually monitored through a salt spray test. The sample surface was scratched down to the metal substrate using a utility knife. The sample was then sprayed with 5% sodium chloride salt spray for 12 hours followed by 12 hours of drying, and this cycle was repeated for 60 days. The corrosion products on the sample surface were then observed. Figure 2As can be seen, the pure epoxy coating blistered and a large amount of corrosion products seeped out after 30 days, while the nanocomposite coating only had a small amount of corrosion products at the scratches.

[0045] The corrosion resistance of a pure epoxy coating and a dual-layer, multifunctional epoxy coating with anti-corrosion and anti-UV aging properties were evaluated using an electrochemical workstation, PARSTAT 4000+. A three-electrode system was employed, including an auxiliary electrode (4 cm). 2 The platinum sheet, working electrode (coated steel plate), and reference electrode (saturated calomel electrode, SCE) were tested in a 3.5 wt.% sodium chloride solution. Before the experiment, the open-circuit potential of the sample was measured in a corrosive medium, and the changes in open-circuit potential were recorded. After the open-circuit potential stabilized, electrochemical impedance spectroscopy was performed, with the test frequency range set to 10 Hz. 5 The amplitude of the AC sinusoidal disturbance signal is 20 mV and the range is from Hz to 0.01 Hz.

[0046] Figure 3 The electrochemical impedance spectroscopy (EIS) results are shown after immersion in 3.5 wt.% NaCl solution for 40 days. The EIS values ​​indicate that, before UV irradiation, the impedance modulus of the dual-layer anti-corrosion and UV-aging multifunctional epoxy coating is significantly higher than that of the pure epoxy sample. At a low frequency of 0.01 Hz, the impedance values ​​of both the dual-layer anti-corrosion and UV-aging multifunctional epoxy coating and the pure epoxy coating are 7.6 × 10⁻⁶. 9 Ω.cm 2 and 4.7×10 8 Ω.cm 2 The impedance values ​​improved by an order of magnitude, demonstrating the effectiveness of nanofillers in enhancing corrosion resistance. After a period of UV irradiation, the impedance values ​​of all samples decreased, indicating that UV radiation damages the protective ability of the coating. At day 20 of immersion, the impedance values ​​of the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating and the pure epoxy coating were 5.3 × 10⁻⁶. 8 Ω.cm 2 and 1.1×10 5 Ω.cm 2 It is evident that pure epoxy coatings have lost their anti-corrosion properties, while dual-layer anti-corrosion and anti-UV aging multifunctional epoxy coatings have superior UV aging resistance.

[0047] To evaluate the UV aging resistance of the composite coating and understand the underlying mechanisms, an accelerated UV aging tester was used to simulate the irradiation aging process of the coating samples. Figure 4 As shown. Specifically:

[0048] According to ISO 16474–2021 standard, UVB lamps (20 × 3 W) with a wavelength range of 313 nm were used. During the UV radiation test, an alternating cycle of irradiation (8 h) and darkness (4 h) was performed, with a cumulative irradiation time of 240 h. After the simulation experiment, the corrosion resistance was investigated using the same measurement conditions described above. The effect of UV radiation on the coating structure was observed using an optical camera.

[0049] Figure 4 This study examines the surface changes of pure epoxy coatings and dual-layer anti-corrosion and anti-UV aging multifunctional epoxy coatings after UV exposure. The PE sample exhibited a significant color change, shifting from white to yellow, attributed to the ring-opening reaction of benzene-containing materials induced by UV damage, while the Ep / F-GO@CNTs sample maintained a relatively stable color. Subsequent SEM analysis of the PE and Ep / F-GO@CNTs samples revealed defects and porosity on the PE surface before UV irradiation, likely due to solvent evaporation during curing. In contrast, the Ep / F-GO@CNTs surface was relatively smooth with significantly fewer defects and porosity. Under UV irradiation, extensive deep cracks appeared on the PE surface, forming a network pattern on the PE coating surface. Most of these cracks originated from existing pores and pits. Figure 5 This provides a pathway 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 enhanced resistance to UV-induced degradation.

[0050] Example 2

[0051] Q235 steel plate was used as the substrate for the coating and was 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.

[0052] For the silane sol-gel layer, a mixture of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTS) was used to enhance the corrosion resistance of the steel substrate. The silane mixture with a TEOS / APTS mass ratio of 70:30 was used to form a more continuous and dense coating, exhibiting superior corrosion resistance compared to single silanes. The silane sol-gel layer was prepared by dip-coating and then dried in an oven at 80°C for 2 hours before use.

[0053] 500 mg of carbon black was mixed with a 1:3 (v / v) HNO3 / H2SO4 mixture, both at a concentration of 5 mol, and refluxed at 100 °C for 3 h to obtain modified carbon black. 30 mL of GO solution (concentration 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 the mixture was ultrasonically treated for 30 min. Afterward, the reaction was magnetically stirred at room temperature for 5 h. The resulting mixture was poured into a 100 mL Teflon-lined autoclave and heat-treated at 120 °C for 12 h. Finally, when the autoclave temperature dropped to room temperature, the autoclave was opened, the solution was centrifuged, and washed repeatedly with water and ethanol. The resulting precipitate (i.e., the synthesized GO@CB) was dried in an oven at 60 °C.

[0054] 5 mL of APTES was mixed with 95 mL of deionized water and stirred with a magnetic stirrer for 120 min. During stirring, 0.5 g of GO@CB nanohybrid material was added. Stirring was continued for another 60 min with a magnetic stirrer, followed by ultrasonic homogenization for 10 min. The suspension was refluxed at 100 °C and stirred continuously for 12 h. To remove residual silane compounds adhering to the nanomaterials, the suspension was centrifuged and washed twice with water. Finally, the product (i.e., the synthesized F-GO@CB) was dried in an oven at 80 °C to obtain the modified nanofiller.

[0055] 75 mg of the modified nanofiller was dissolved in 10 mL of deionized water and stirred for 60 min, followed by ultrasonic treatment for 60 min. The resulting solution was then added to 100 g of epoxy resin and stirred until a homogeneous mixture was obtained, followed by further ultrasonic treatment for 10 min. Subsequently, 50 g of hardener was added to the mixture, and the mixture was degassed and applied to a metal substrate to successfully prepare a 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 coating structure.

[0056] The corrosion resistance of the aforementioned dual-layer anti-corrosion and UV-aging-resistant multifunctional epoxy coating was evaluated using electrochemical impedance spectroscopy and salt spray tests. After three months of exposure to strong UV radiation outdoors, the UV resistance of the coating was again observed and electrochemically evaluated. The results showed that the prepared dual-layer anti-corrosion and UV-aging-resistant multifunctional epoxy coating exhibited superior UV aging resistance and corrosion protection compared to the pure epoxy coating. Furthermore, the addition of nanofillers and the dual-layer structure significantly increased the coating's adhesion strength.

[0057] Example 3

[0058] The substrate was AA2024-T3 aluminum alloy. The sample was etched in a 50 g / L sodium hydroxide solution for 30 s and then in a 400 g / L nitric acid solution for 30 s at room temperature. Finally, the substrate surface was rinsed with deionized water and air-dried.

[0059] For the silane sol-gel layer, a mixture of methyltriethoxysilane (MTES) and 3-glycidyloxypropyltrimethoxysilane (GPTMS) with a mass ratio of MTES / GPTMS of 30:1 was used. The silane sol-gel layer was prepared by dip-coating and then dried in an oven at 80°C for 2 hours before use.

[0060] 500 mg of carbon nanoparticles (CH) were stirred with a mixture of HNO3 / H2SO4 (1:3, v / v) at a concentration of 5 mol / L and refluxed at 100 °C for 3 h to obtain modified carbon nanoparticles. 30 mL of GO solution (10 mg / mL) and 30 mL of ethanol were mixed and stirred for 60 min. Then, 0.015 g of the modified carbon nanoparticles were added to the mixture and ultrasonically treated for 60 min. The reaction was then magnetically stirred at room temperature for 5 h. The resulting mixture was poured into a 100 mL Teflon-lined autoclave and heat-treated at 60 °C for 24 h. Finally, when the autoclave temperature dropped to room temperature, the autoclave was opened, the solution was centrifuged, and washed repeatedly with water and ethanol. The precipitate (i.e., the synthesized GO@CH) was dried in an oven at 60 °C to obtain the nanofiller.

[0061] 15 g of nanofiller was dissolved in 30 mL of deionized water and stirred for 120 min, followed by ultrasonic treatment for 60 min. The resulting solution was then added to 100 g of epoxy resin and stirred until a homogeneous mixture was obtained, followed by probe ultrasonic treatment for 10 min. Subsequently, 50 g of hardener was added to the mixture and stirred until homogeneous, then coated onto a prepared silane sol-gel layer to successfully prepare a double-layer corrosion-resistant and UV-resistant 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.

[0062] The corrosion resistance of the aforementioned dual-layer anti-corrosion and UV-aging-resistant multifunctional epoxy coating was evaluated using electrochemical testing, salt spray testing, and corrosion product analysis. The coatings were then exposed to strong outdoor UV radiation for three months, after which their UV resistance was observed and electrochemically assessed again. The results showed that the prepared dual-layer anti-corrosion and UV-aging-resistant multifunctional epoxy coating exhibited superior UV aging resistance and corrosion protection compared to the pure epoxy coating. Furthermore, the addition of nanofillers and the dual-layer structure significantly improved the coating's surface hydrophobicity and mechanical properties.

[0063] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0064] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0065] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0066] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0067] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

[0068] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this patent should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed inventive subject matter.

Claims

1. A method for preparing a double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating, characterized in that, The epoxy coating includes a silane sol-gel layer and a nanocomposite coating, with the nanocomposite coating located above the silane sol-gel layer. The preparation process of the silyl sol-gel layer is as follows: two silyl groups are mixed in a mass ratio of (1~30):1; the silyl sol-gel layer includes two of tetraethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane and 3-glycidyloxypropyltrimethoxysilane. The preparation process of the nanocomposite coating is as follows: Two carbon nanomaterials are mixed in a hybrid ratio of easily dispersible material to poorly dispersible material of (20~1):

1. The nanocomposite coating uses two of the following: graphene, graphene oxide, multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black, and carbon nanofibers. The easily dispersible materials include graphene and graphene oxide, while the poorly dispersible materials include multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon black, and carbon nanofibers. After mixing, nanofillers are synthesized by hydrothermal or solvothermal methods. Subsequently, the nanofillers are added to the coating matrix, with the amount of nanofillers added accounting for 0.05~10 wt.% of the coating matrix. Before being added to the coating matrix, the nanofiller is modified by a silane coupling agent to obtain the modified nanofiller.

2. The method for preparing the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating according to claim 1, characterized in that, When synthesizing nanofillers using the hydrothermal method, the nanofillers are heat-treated in deionized water at 80–200°C for 4–24 h; when synthesizing nanofillers using the solvothermal method, the nanofillers are heat-treated in a mixture of deionized water and an organic solvent at 60–120°C for 10–24 h, where the organic solvent is ethanol or acetone.

3. The method for preparing the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating according to claim 1, characterized in that, The coating matrix is ​​made of epoxy resin.

4. The method for preparing the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating according to claim 1, characterized in that, The nanofiller is diluted with a solvent to form a thin, watery solution or paste, which is then uniformly dispersed and added to the coating matrix, and finally a curing agent is added.

5. An application of a double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating prepared by the preparation method according to any one of claims 1-4, characterized in that, The silane sol-gel layer and the nanocomposite coating were sequentially coated onto the pretreated metal substrate surface.

6. The application of the double-layer anti-corrosion and anti-UV aging multifunctional epoxy coating according to claim 5, characterized in that, The coating thickness of the nanocomposite coating ranges from 1 to 1000 µm.

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