Preparation method of MXene / hydrophobic modified SiC synergistically reinforced polyurethane anticorrosion composite coating

Abstract

The application discloses a preparation method of an MXene / hydrophobic modified SiC synergistically reinforced polyurethane anticorrosion composite coating, and aims at the technical defects that micro-pores and micro-cracks are easily generated during curing of a traditional water-based polyurethane coating, the structure is insufficient in compactness, long-acting anticorrosion capacity is insufficient, a single MXene filler is prone to agglomeration, poor in dispersibility and single in protection form, the application adopts perfluorodecyl triethoxysilane to hydrophobically modify SiC powder, and modified SiC is compounded with MXene to build a double-filler synergistic protection system.The application utilizes modified SiC to optimize the microstructure of the coating by interstitial reinforcement, combines the MXene sheet labyrinth barrier effect, combines ultrasonic pre-dispersion and a segmented gradient curing process, and builds a dense protection structure coupled with hydrophobic protection and physical barrier.The application significantly improves the medium barrier and electrochemical anticorrosion performance of the coating, can be adapted to harsh corrosion working conditions such as high humidity and salt spray, effectively prolongs the service life of a metal base material, is simple and controllable in process, stable in performance, and has wide engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of metal anti-corrosion coating technology, specifically relating to a method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating. Background Technology

[0002] Waterborne polyurethane (WPU) is an important material for replacing traditional solvent-based coatings and developing green and environmentally friendly anti-corrosion coatings due to its advantages such as being environmentally friendly and pollution-free, having excellent adhesion properties, good mechanical properties, and wide substrate compatibility. It can stably adhere to the surfaces of various substrates such as glass, polymer fibers, and metals, and has good potential for basic anti-corrosion applications. However, pure waterborne polyurethane systems have inherent defects. The polyurethane matrix has poor hydrolysis resistance, and after film formation, residual polar hydrophilic groups such as hydroxyl and amino groups in the system lead to insufficient hydrophobicity and density of the coating, making it easy for corrosive media to penetrate and diffuse. At the same time, the non-uniform evaporation of water during film formation can easily cause structural defects such as microcracks and micropores inside the coating, which significantly reduces the long-term anti-corrosion performance and weather resistance of waterborne polyurethane coatings, limiting its large-scale application in high-end anti-corrosion fields.

[0003] To improve the overall anti-corrosion performance of waterborne polyurethane coatings, traditional techniques generally optimize the polyurethane system through crosslinking modification, nanofiller doping, and structural regulation. Currently, extensive research has been conducted both domestically and internationally on the modification of polyurethane anti-corrosion coatings, as detailed below:

[0004] Reference 1 (Zhou J, Tang L. Performance enhancement of waterborne polyurethane acrylate via multi-crosslinking and its application as anti-corrosion coating[J]. Progress in Organic Coatings, 2026, 214: 110051.) discloses a multi-crosslinked waterborne polyurethane acrylate anti-corrosion coating system. Using pentaerythritol triacrylate as a precursor, a composite coating material is prepared by combining UV-initiated crosslinking technology. Ethylenediamine and diethylenetriamine are selected as chain extenders to pre-construct branched crosslinked structures in the system. 3-aminopropyltrimethoxysilane is used for localized blocking modification of the system, relying on the self-condensation reaction of siloxane to form an auxiliary crosslinking network. This modification method can effectively improve the degree of crosslinking and surface hydrophobicity of the coating, and improve the coating's water resistance, mechanical strength, and corrosion resistance. However, the filling effect of simple crosslinking modification on micro-defects in the coating is limited, and the long-term protective performance still has shortcomings.

[0005] Reference 2 (Xu H, Shen L, Ruijie F, et al. Anti-corrosion performance of polyurethane nanocomposite coating based on new graphene nanosheets with low lattice defects and high conductivity[J]. Surfaces and Interfaces, 2025:107412) discloses a method for preparing a waterborne polyurethane anti-corrosion coating modified with graphene and characterized by low lattice defects and high conductivity. Related studies have confirmed that low-doped (0.075 wt%) graphene can significantly enhance the performance of polyurethane coatings, increasing the coating adhesion from 4.7 MPa to 8.9 MPa and reducing the corrosion rate of the metal substrate from 1.7 × 10 mm / year to 2.4 × 10 mm / year. By controlling the microstructure of graphene, the physical barrier and electrochemical anti-corrosion capabilities of the coating can be simultaneously improved. However, graphene fillers suffer from easy agglomeration and poor dispersion uniformity, making it difficult to simultaneously achieve coating density, stability, and long-term anti-corrosion performance through single filler modification.

[0006] Reference 3 (Yi P, Mo J, Liu R, et al. Study on corrosion behavior of waterborne polyurethane coating with high thermal conductivity[J]. Applied Sciences, 2022, 12(4): 202) discloses the synergistic strengthening mechanism of multi-scale fillers. It introduces a composite of carbon nanotubes and graphene into a polyurethane coating system, effectively optimizing the coating's microstructure and improving the overall performance of the composite material by utilizing the dimensional complementarity effect of the multi-scale fillers. When the total filler content is 2 wt%, the coating achieves optimal thermal conductivity and corrosion resistance, verifying the technical advantages of multi-component filler synergistic modification compared to single fillers, and providing theoretical support for the modification of polyurethane anti-corrosion systems with composite fillers. However, this system is limited to carbon-based filler composites, resulting in a single filler system and limited ability to repair micro-defects in the coating, making it difficult to meet the long-term protection requirements under highly corrosive conditions.

[0007] Reference 4 (Lou D, Chen H, Liu J, et al. Improved anticorrosion properties of polyurethane nanocomposites by Ti3C2Tx MXene / functionalized carbon nanotubes for corrosion protection coatings[J]. ACS Applied Nano Materials, 2023, 6(13): 12515-12525) addresses the shortcomings of MXene-based polyurethane composite coatings, such as poor dispersibility and insufficient storage stability, by using Ti3C2Tx MXene / functionalized carbon nanotubes. x MXene was combined with functionalized carbon nanotubes as a composite modified filler, and the effects of the composite filler on the thermal stability, surface hydrophobicity, roughness, and mechanical properties of the coating were systematically investigated. Experimental results showed that when the MXene content was 0.95 wt% and the carbon nanotube content was 0.05 wt%, the corrosion rate of the polyurethane coating was as low as 2.1 × 10 μm / year. Trace amounts of carbon nanotubes significantly optimized the anti-corrosion performance of the MXene-based polyurethane coating, further confirming the superiority of synergistic modification with multiple fillers. However, this modified system still has inherent technical defects, failing to effectively solve the problems of easy oxidation and failure of MXene, poor compatibility of different fillers, and uneven component distribution after film formation. Furthermore, the coating lacks self-healing ability for microcracks, and its protective performance deteriorates significantly after long-term service.

[0008] In summary, while existing research has explored conventional techniques such as crosslinking modification, single carbon filler modification, and MXene / carbon nanotube composite modification, which can improve the basic anti-corrosion performance of waterborne polyurethane coatings to some extent, each has its own technical limitations. These limitations include insufficient compatibility of filler systems, incomplete repair of micro-defects, poor coating stability, and lack of self-healing ability, making it difficult to meet the long-term anti-corrosion requirements under harsh industrial conditions. To further clarify the engineering application value of polyurethane materials and the necessity of developing this technology, reference 5 (Traber B, Odermatt D, Jung H, et al. Strukturelles Kleben mit isocyanat-freien Polyurethanhybriden[J]. adhäsionKLEBEN&DICHTEN, 2025, 69(1): 30-35) confirms the excellent engineering adaptability of polyurethane materials. With its unique advantages such as light weight and excellent adhesion, this material can be widely adapted to various scenarios such as building insulation, cold chain equipment, and industrial structural bonding. It can effectively reduce the self-weight of the substrate and improve the service life of metal, concrete, and wood substrates, demonstrating its wide range of applications and outstanding practical value. Therefore, developing a novel polyurethane composite coating preparation technology with multi-filler synergistic modification, dense and stable structure, and long-term corrosion resistance has significant engineering application value and research significance. Summary of the Invention

[0009] To address the technical problems of existing waterborne polyurethane coatings, such as easy structural defects during curing, insufficient hydrophobicity and density, limited long-term anti-corrosion performance, poor dispersibility of single MXene filler modification systems, and limited protection methods, the present invention aims to provide a method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, comprising the following steps: S1. Preparation of hydrophobically modified SiC powder: SiC powder is hydrophobically modified by perfluorodecyltriethoxysilane. Fluorohydrophobic groups are grafted onto the surface of SiC powder through silane bonding reaction, giving SiC powder hydrophobic properties. The resulting hydrophobically modified SiC powder can be combined with MXene to construct a hydrophobic-barrier synergistic protection system. S2. Preparation of polyurethane anti-corrosion composite coating: The steel substrate is pretreated; MXene powder is compounded and dispersed with the aforementioned hydrophobic modified SiC powder, the complementary properties of the two can optimize the micro-density of the coating; then it is mixed evenly with waterborne polyurethane component A, dispersant and waterborne polyurethane component B as curing agent to obtain composite coating slurry; wherein waterborne polyurethane components A and B are conventional raw materials for two-component waterborne polyurethane coatings, component A is hydroxyl-containing polyurethane main resin, and component B is hydrophilic polyisocyanate curing agent, the two undergo cross-linking reaction after mixing to form a complete coating film; the obtained composite coating slurry is coated on the surface of the pretreated substrate, and cured in stages to obtain MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating.

[0011] Preferably, in step S1, the mass ratio of the SiC powder to perfluorodecyltriethoxysilane is 1:0.5-1.

[0012] Preferably, in step S1, the reaction temperature for the hydrophobic modification treatment is 45–55°C, and the reaction time is 25–35 min.

[0013] Preferably, the steel substrate is Q235 steel, and the substrate pretreatment process is as follows: after grinding the steel surface with 600-grit sandpaper to remove rust and dirt, it is immersed in NaOH solution for 1-2 hours to complete the substrate surface pretreatment.

[0014] Preferably, in step S2, the segmented curing molding process is as follows: curing at room temperature for 20–28 h, followed by constant temperature curing at 55–65°C for 10–14 h.

[0015] Preferably, the preparation process of the composite coating slurry is as follows: MXene powder and hydrophobically modified SiC powder are mixed, and anhydrous ethanol is added for ultrasonic dispersion for 25-35 min; then, waterborne polyurethane component A, dispersant, and waterborne polyurethane component B curing agent are added sequentially, and each component is stirred for 10-20 min after addition to obtain a uniform mixture, thus obtaining the composite coating slurry. This invention employs a process of first ultrasonically pre-dispersing the filler, followed by stepwise addition and stirring, which can effectively improve the dispersion uniformity of the two fillers in the polyurethane matrix, inhibit filler agglomeration, and improve interface defects.

[0016] Preferably, the mass ratio of MXene powder to hydrophobically modified SiC powder is 1:2 to 1:5.

[0017] A second aspect of the present invention provides an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating prepared by the above preparation method.

[0018] This invention constructs an integrated anti-corrosion system that combines microstructural reinforcement, physical barrier, and surface hydrophobic protection by synergistically modifying polyurethane coatings with hydrophobically modified SiC and MXene dual fillers. Specifically, the SiC powder modified with perfluorodecyltriethoxysilane has stable fluorinated hydrophobic groups grafted onto its surface, effectively improving the interfacial compatibility between the inorganic filler and the organic polyurethane matrix, inhibiting filler agglomeration, and mitigating interfacial defects caused by uneven filler dispersion. Simultaneously, the micron-sized modified SiC particles exert a gap-filling reinforcement effect, effectively filling structural defects such as micropores and microcracks caused by solvent evaporation during polyurethane resin curing, thereby enhancing the overall density and structural stability of the coating.

[0019] Two-dimensional layered MXene nanosheets can form an interlaced barrier network within the coating, effectively extending the penetration and diffusion paths of corrosive media such as water, oxygen, and chloride ions, significantly reducing the penetration rate of corrosive media, and achieving long-term physical shielding protection. The two fillers complement each other and synergistically enhance each other's performance, avoiding the technical shortcomings of single MXene filler, such as limited protection, susceptibility to local dispersion defects, and insufficient long-term protection performance. By combining the surface hydrophobic and seepage-inhibiting properties of hydrophobically modified SiC with the layered shielding properties of MXene, a multi-integrated protection mechanism of "hydrophobic water blocking, layered barrier, and dense structural reinforcement" is synergistically constructed.

[0020] Meanwhile, by optimizing the compounding ratio of the two fillers, ultrasonic pre-dispersion and segmented curing process, this invention further ensures the uniform dispersion of the fillers in the matrix, maximizes the synergistic protective advantages of the two fillers, effectively improves the electrochemical corrosion resistance of the coating, reduces the corrosion current density, and enhances the coating impedance stability. This allows the composite coating to maintain stable protective capabilities under harsh corrosion conditions such as high humidity and salt spray, significantly improving the long-term service life of the substrate.

[0021] Beneficial effects (1) This invention uses perfluorodecyltriethoxysilane to hydrophobically modify SiC powder, which effectively improves the interfacial compatibility between inorganic fillers and polyurethane organic matrix, overcoming the technical problems of easy agglomeration of unmodified inorganic fillers, weak interfacial bonding, and many coating pores and cracks. Modified SiC particles can play a gap-filling and reinforcing role. Combined with the layered shielding characteristics of two-dimensional MXene nanosheets, they interweave to construct a three-dimensional dense protective network in the polyurethane matrix, effectively filling the micropores generated by coating curing, reducing structural defects, and significantly improving the structural density and overall stability of the composite coating.

[0022] (2) This invention utilizes the interlayer barrier effect of MXene nanosheets to effectively extend the penetration path of corrosive media such as water, oxygen, and chloride ions, thereby reducing the penetration rate of the media. At the same time, by grafting fluorinated hydrophobic groups onto the SiC surface, the wettability of the coating surface is reduced, inhibiting the adsorption and penetration of water molecules. The two fillers complement each other and work synergistically to make up for the shortcomings of single filler modification and protection, and to construct a dual protection mechanism that couples physical barrier and hydrophobic protection, significantly improving the medium barrier capability and long-term anti-corrosion performance of the coating.

[0023] (3) By optimizing the composite system of MXene and hydrophobically modified SiC, this invention effectively solves the problems of agglomeration, uneven dispersion, increased interface defects, and decreased protective performance caused by filler ratio imbalance. The composite coating prepared by this invention exhibits a positive shift in corrosion potential, a significant reduction in corrosion current density, and excellent low-frequency electrochemical impedance stability. Its comprehensive anti-corrosion performance is significantly better than that of pure polyurethane coatings and single filler modified coatings. It can be adapted to harsh corrosive conditions such as high humidity and salt spray, effectively extending the service life of carbon steel substrates. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 FT-IR infrared spectra of the etching precursor TiAlC raw material and the MXene sample prepared by etching; Figure 2 XRD crystal structure diagrams of the etching precursor TiAlC raw material and the MXene sample prepared by etching; Figure 3 XPS full spectrum of the etching precursor TiAlC raw material and the MXene sample prepared by etching; Figure 4 The images show the FT-IR infrared spectra of SiC powder before and after hydrophobic modification. Figure 5 The XRD crystal structure diagrams of SiC powder before and after hydrophobic modification are shown. Figure 6 XPS full spectrum of SiC powder before and after hydrophobic modification; Figure 7 SEM microstructure images of different coating sections prepared for comparative examples 1–5: (a) pure PU coating; (b) MPU coating; (c) SPU coating; (d) MSPU coating. 3:1 Coating; (e)MSPU 1:1 coating; Figure 8 Static water contact angle test results for different coated samples prepared in Comparative Examples 1-5; Figure 9 Tafel dynamic polarization curves of bare steel and comparative examples 1-5 with different coatings; Figure 10 Electrochemical impedance spectroscopy (EIS) of different coated samples after immersion in 0.5 wt% NaCl solution for 48 h: (a) Nyquist impedance arc diagram; (b) Bode impedance modulus diagram; (c) Bode phase angle diagram. Figure 11 This is a process flow diagram of the present invention. Detailed Implementation

[0026] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0027] Example 1 Reference Figure 11 A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, the specific preparation steps are as follows: (1) Pretreatment of Q235 carbon steel substrate Q235 carbon steel was selected as the substrate for coating adhesion. The surface of the carbon steel was polished with 600-grit sandpaper to remove rust, oxide layer and attached stains. Then the polished carbon steel substrate was immersed in the prepared sodium hydroxide solution for 2 hours to completely remove oil stains from the substrate surface and complete the substrate cleaning pretreatment for later use.

[0028] (2) Preparation of monolayer / few-layer MXene nanosheets Weigh 3.2 g of lithium fluoride (LiF) and completely dissolve it in a polytetrafluoroethylene reactor containing 40 mL of 9 mol / L hydrochloric acid (HCl) solution. Stir continuously for 10 min to form a homogeneous mixture. Slowly add 2 g of 200 mesh TiAlC powder to the mixture and etch continuously at a constant temperature of 40 ℃ for 48 h to achieve interlayer etching and stripping of TiAlC.

[0029] After the etching reaction is completed, the product is acid-washed 2-3 times with 1 mol / L hydrochloric acid solution. After each acid wash, the product is centrifuged at 3500 rpm for 1 min. The product is then washed and centrifuged multiple times with water at 3500 rpm for 1 min each time until the product precipitate expands significantly and the supernatant turns dark green.

[0030] The washed product was placed in an argon-protected ice-water bath and sonicated at an ultrasonic frequency of 80 kHz for 60 min to fully exfoliate and obtain a single / few-layer MXene sheet structure. Finally, it was centrifuged at 5500 rpm for 10 min, and the supernatant was collected. After freeze-drying, the single / few-layer MXene powder was obtained for later use.

[0031] (3) Preparation of hydrophobically modified SiC powder Take 1.0 g of SiC powder and 50 mL of anhydrous ethanol and place them in a beaker. Disperse them by ultrasonication for 30 min to obtain a uniform and stable SiC suspension. Weigh 1.0 g of perfluorodecyltriethoxysilane (PFDS) and add it to the anhydrous ethanol system diluted with deionized water. Stir thoroughly to dissolve and prepare a uniform silane modifier solution.

[0032] The pretreated SiC suspension was added to the silane modifier solution, stirred until homogeneous, and then ultrasonically dispersed for 30 min. The mixture was then placed in a constant-temperature water bath at 50 ℃ for silane bonding modification. After the modification reaction, the modified product was purified by centrifugation with anhydrous ethanol: the mixture was divided into centrifuge tubes, anhydrous ethanol was added to bring the volume to a uniform mark, and the tubes were symmetrically placed in a centrifuge for centrifugation. After centrifugation, the supernatant was discarded. The anhydrous ethanol centrifugation and washing operation was repeated 2-3 times to thoroughly remove unreacted silane reagents and impurities from the system. The washed solid product was dried in a vacuum drying oven at 60 ℃ for 24 h to finally obtain hydrophobic modified SiC powder.

[0033] (4) Preparation of polyurethane anti-corrosion composite coating Take appropriate amounts of the prepared single / few-layer MXene powder and hydrophobic modified SiC powder, mix them, add anhydrous ethanol, and ultrasonically disperse for 30 min to achieve uniform dispersion of the two fillers; add waterborne polyurethane component A to the uniformly dispersed filler system and magnetically stir for 15 min; then add 3 drops of dispersant, then add waterborne polyurethane component B curing agent, and continue magnetically stirring for 15 min. After thorough mixing, a uniform and stable MXene / hydrophobic modified SiC composite polyurethane coating slurry is obtained.

[0034] The prepared composite coating slurry was loaded into a spraying device and sprayed uniformly onto the surface of the pretreated Q235 carbon steel substrate, ensuring uniform coating thickness and complete spraying area. After spraying, the sample was first cured at room temperature for 24 h, and then transferred to a constant temperature environment of 60℃ for 12 h. After segmented curing, the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating was finally obtained and marked as MSPU-1 coating.

[0035] Example 2 A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, the specific preparation steps are as follows: (1) Pretreatment of Q235 carbon steel substrate The substrate pretreatment process in this step is the same as in Example 1.

[0036] (2) Preparation of monolayer / few-layer MXene nanosheets Weigh 4.8 g of lithium fluoride (LiF) and completely dissolve it in a polytetrafluoroethylene reactor containing 48 mL of 12 mol / L hydrochloric acid solution. Stir continuously for 10 min to form a homogeneous mixture. Slowly add 2.4 g of 200 mesh TiAlC powder to the mixture and etch continuously at a constant temperature of 42 ℃ for 48 h to achieve interlayer etching and stripping of TiAlC.

[0037] After the etching reaction is completed, single / few-layer MXene powder is prepared by post-processing (same as in Example 1) for later use.

[0038] (3) Preparation of hydrophobically modified SiC powder Take 2.0 g of SiC powder and 100 mL of anhydrous ethanol and place them in a beaker. Disperse them by ultrasonication for 30 min to obtain a uniform and stable SiC suspension. Weigh 2.1 g of perfluorodecyltriethoxysilane (PFDS) and add it to a mixture of anhydrous ethanol diluted with deionized water. Stir and dissolve thoroughly to prepare a uniform silane modifier solution.

[0039] The SiC suspension was added to the silane modifier solution, stirred until homogeneous, and then ultrasonically dispersed for 40 min. The mixture was then placed in a constant-temperature water bath at 52℃ for silane bonding modification. After the modification reaction, the modified product was washed by centrifugation with anhydrous ethanol and dried in a vacuum drying oven at 55℃ for 24 h to finally obtain hydrophobic modified SiC powder.

[0040] (4) Coating preparation This step is the same as in Example 1, and finally an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating is obtained, which is marked as MSPU-2 coating.

[0041] Example 3 A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, the specific preparation steps are as follows: (1) Pretreatment of Q235 carbon steel substrate The substrate pretreatment process in this step is the same as in Example 1.

[0042] (2) Preparation of monolayer / few-layer MXene nanosheets 3.2 g of lithium fluoride (LiF) was weighed and completely dissolved in a polytetrafluoroethylene reactor containing 42 mL of 10 mol / L hydrochloric acid solution. The mixture was stirred continuously for 10 min to form a homogeneous mixture. 2.2 g of 300-mesh TiAlC powder was slowly added to the mixture, and the mixture was etched under constant temperature of 43 °C for 48 h with continuous stirring to achieve interlayer etching and stripping of TiAlC. After the etching reaction was completed, single / few-layer MXene powder was obtained through post-processing (same as Example 1) for later use.

[0043] (3) Preparation of hydrophobically modified SiC powder Take 1.0 g of SiC powder and 52 mL of anhydrous ethanol and place them in a beaker. Disperse them by ultrasonication for 30 min to obtain a uniform and stable SiC suspension. Weigh 1.29 g of perfluorodecyltriethoxysilane (PFDS) and add it to a mixture of anhydrous ethanol diluted with deionized water. Stir thoroughly to dissolve and prepare a uniform silane modifier solution.

[0044] The SiC suspension was added to the silane modifier solution, stirred until homogeneous, and then ultrasonically dispersed for 35 min. The mixture was then placed in a constant-temperature water bath at 50 ℃ for silane bonding modification. After the modification reaction, the modified product was washed by centrifugation with anhydrous ethanol and dried in a vacuum drying oven at 50 ℃ for 36 h to finally obtain hydrophobic modified SiC powder.

[0045] (4) Coating preparation This step is the same as in Example 1, and finally an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating is obtained, which is marked as MSPU-3 coating.

[0046] Example 4 A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, the specific preparation steps are as follows: (1) Pretreatment of Q235 carbon steel substrate The substrate pretreatment process in this step is the same as in Example 1.

[0047] (2) Preparation of monolayer / few-layer MXene nanosheets Weigh 3.6 g of lithium fluoride (LiF) and completely dissolve it in a polytetrafluoroethylene reactor containing 45 mL of 9 mol / L hydrochloric acid solution. Stir continuously for 10 min to form a homogeneous mixture. Slowly add 2 g of 300 mesh TiAlC powder to the mixture and etch continuously at a constant temperature of 45 ℃ for 48 h to achieve interlayer etching and stripping of TiAlC.

[0048] After the etching reaction is completed, a single / few-layer MXene powder is prepared by post-processing (same as in Example 1) for later use.

[0049] (3) Preparation of hydrophobically modified SiC powder Take 1.2 g of SiC powder and 60 mL of anhydrous ethanol and place them in a beaker. Disperse them by ultrasonication for 10 min to obtain a uniform and stable SiC suspension. Weigh 1.2 g of perfluorodecyltriethoxysilane (PFDS) and add it to a mixed solvent of deionized water and anhydrous ethanol. Stir thoroughly to dissolve and prepare a uniform silane modifier solution.

[0050] The SiC suspension was added to the silane modifier solution, stirred and mixed evenly, and then ultrasonically dispersed for 30 min. The mixture was then placed in a constant-temperature water bath at 55℃ for silane bonding modification. After the modification reaction, the modified product was washed by centrifugation with anhydrous ethanol and dried in a vacuum drying oven at 60℃ for 24 h to finally obtain hydrophobic modified SiC powder.

[0051] (4) Coating preparation This step is the same as in Example 1, and finally an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating is obtained, which is marked as MSPU-4 coating.

[0052] Example 5 A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, the specific preparation steps are as follows: (1) Pretreatment of Q235 carbon steel substrate The substrate pretreatment process in this step is the same as in Example 1.

[0053] (2) Preparation of monolayer / few-layer MXene nanosheets 3.2 g of lithium fluoride (LiF) was dissolved in 39 mL of 10 mol / L hydrochloric acid solution and stirred continuously for 10 min to form a homogeneous mixture. 2.5 g of 200 mesh TiAlC powder was slowly added to the mixture and etched at 42 ℃ for 48 h to achieve interlayer etching and stripping of TiAlC.

[0054] After the etching reaction is completed, a single / few-layer MXene powder is prepared by post-processing (same as in Example 1) for later use.

[0055] (3) Preparation of hydrophobically modified SiC powder Take 4.0 g of SiC powder and 200 mL of anhydrous ethanol and place them in a beaker. Disperse them by ultrasonication for 30 min to obtain a uniform and stable SiC suspension. Weigh 4.2 g of perfluorodecyltriethoxysilane (PFDS) and add it to a mixed solvent of deionized water and anhydrous ethanol. Stir thoroughly to dissolve and prepare a uniform silane modifier solution.

[0056] The SiC suspension was added to the silane modifier solution, stirred and mixed evenly, and then ultrasonically dispersed for 60 min. The mixture was then placed in a constant-temperature water bath at 57℃ for silane bonding modification. After the modification reaction, the modified product was washed by centrifugation with anhydrous ethanol and dried in a vacuum drying oven at 60℃ for 48 h to obtain hydrophobic modified SiC powder.

[0057] (4) Coating preparation This step is the same as in Example 1, and finally an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating is obtained, which is marked as MSPU-5 coating.

[0058] Comparative Example 1 The process of this comparative example is basically the same as that of Example 1, except that MXene and hydrophobically modified SiC functional fillers are not introduced into the system, and a pure water-based polyurethane blank coating is finally obtained, labeled as PU.

[0059] Comparative Example 2 The process of this comparative example is basically the same as that of Example 2, except that only MXene filler is introduced into the system and no hydrophobic modified SiC filler is added. Finally, a single MXene-reinforced polyurethane coating is obtained, which is labeled as MPU.

[0060] Comparative Example 3 The process of this comparative example is basically the same as that of Example 3, except that only hydrophobic modified SiC filler is introduced into the system, and MXene filler is not added. Finally, a single hydrophobic modified SiC reinforced polyurethane coating is obtained, which is labeled as SPU.

[0061] Comparative Example 4 The process of this comparative example is basically the same as that of Example 4, except that the mass ratio of MXene to hydrophobically modified SiC filler is adjusted to 3:1, and a polyurethane anti-corrosion composite coating, labeled as MSPU, is finally obtained. 3:1 .

[0062] Comparative Example 5 The process of this comparative example is basically the same as that of Example 5, except that the mass ratio of MXene to hydrophobically modified SiC filler is adjusted to 1:1, and a polyurethane anti-corrosion composite coating, labeled as MSPU, is finally obtained. 1:1 .

[0063] Characterization and performance testing 1. The TiAlC precursor material and the MXene sample prepared by etching and exfoliation were characterized by FT-IR infrared spectroscopy, XRD crystal structure and XPS energy dispersive spectroscopy. The results are shown in the figure. Figure 1-3 .

[0064] Depend on Figure 1 The results show that at 3434 cm -1 A typical broad absorption peak characteristic of hydroxyl (-OH) groups appeared at the wavenumber. Compared with the original TiAlC curve, the absorption peak of the MXene sample at this position was sharper and the absorption intensity was significantly enhanced, proving that a large number of hydroxyl active groups were successfully introduced into the surface of the MXene material after etching. Meanwhile, at 1044 cm⁻¹... -1 The characteristic absorption peaks observed at these locations further corroborate the effective introduction of alcohol hydroxyl groups onto the MXene surface. The abundant surface-active groups provide a good structural basis for subsequent hydrophobic surface modification and filler interface composites of MXene. Furthermore, the TiAlC and MXene samples exhibited absorption peaks at 1600–1650 cm⁻¹. -1 Sharp absorption peaks characteristic of CO bonds were observed in all regions; unlike the original TiAlC, the MXene spectrum showed a sharp absorption peak at 1520 cm⁻¹. -1 and 552 cm -1 The presence of new characteristic absorption peaks for Ti-OH and Ti-O bonds, along with the differentiation of these characteristic peaks, fully confirms that the process of this invention successfully etched and exfoliated TiAlC to prepare MXene nanosheets with surfaces rich in active groups.

[0065] Depend on Figure 2 The results show that, compared with the original TiAlC sample, the characteristic diffraction peak (002) in the XRD diffraction pattern of MXene nanosheets is significantly shifted, and the full width at half maximum (FWHM) of the diffraction peak is significantly increased. This change is closely related to the structural evolution process of TiAlC aluminum layer removal and sheet peeling during etching. Simultaneously, secondary weak diffraction peaks (004), (006), (008), and (010) appear successively in the MXene diffraction pattern, fully demonstrating that the MXene sheets were successfully peeled off, and the interlayer spacing and microcrystalline structure of the material have significantly changed. Furthermore, the characteristic diffraction peaks corresponding to the original TiAlC completely disappear in the MXene pattern, with no residual raw material characteristic signals. In summary, the XRD characterization results fully confirm that the etching process of this invention can effectively break the original crystal structure of TiAlC, achieve precise etching and peeling of the aluminum layer, and successfully prepare layered MXene nanosheet materials.

[0066] Depend on Figure 3 The results show that, compared with the original TiAlC sample, the characteristic peak of Al element in the XPS full spectrum of MXene nanosheets is significantly weakened and almost disappears, indicating that the interlayer aluminum layer of TiAlC is effectively etched away under the etching action of in-situ HF generation in the LiF / HCl composite etching system. Simultaneously, a clear characteristic response signal of F element appears in the MXene sample spectrum, and the relative content of fluorine element is significantly increased, fully confirming that fluorine-containing functional groups are successfully introduced and grafted onto the surface of the MXene material during the etching process. In summary, the XPS characterization results further confirm that the etching process of this invention can effectively strip the TiAlC aluminum layer, achieve functional group modification of the MXene surface, and stably prepare high-purity, structurally complete layered MXene nanosheet materials.

[0067] 2. The SiC powders before and after hydrophobic modification were characterized by FT-IR infrared spectroscopy, XRD crystal structure, and XPS energy dispersive spectroscopy. The results are shown in the figure. Figure 4-6 .

[0068] Depend on Figure 4 The results show that the modified SiC samples have a viscosity of 1000–1200 cm⁻¹ -1 Several significant characteristic absorption peaks appear in the wavenumber range, including 1145 cm⁻¹. -1 The characteristic peak at 1204 cm⁻¹ is attributed to the stretching vibrations of the COC and Si-OC bonds. -1 The characteristic peaks at these locations correspond to the typical stretching vibrations of the CF bonds in the perfluoroalkyl chain. These characteristic absorption peaks are characteristic responses of the siloxane structure and fluorinated hydrophobic functional groups, fully demonstrating that perfluorodecyltriethoxysilane (PFDS) was successfully grafted onto the surface of SiC powder, achieving hydrophobic modification of the SiC powder.

[0069] Depend on Figure 5 The results show that the positions, shapes, and intensities of the characteristic peaks in the XRD diffraction patterns of the SiC samples before and after modification remained basically consistent, with no new characteristic diffraction peaks or peak disappearances. The reason for this is that the hydrophobic modification of SiC by perfluorodecyltriethoxysilane (PFDS) is merely a surface functional group modification and does not alter the inherent crystal structure of SiC. Therefore, XRD characterization alone is insufficient to determine the success of SiC modification; further comprehensive verification of the modification effect is required by combining FT-IR infrared spectroscopy and XPS energy dispersive spectroscopy results.

[0070] Depend on Figure 6The results show that, compared with the unmodified SiC raw material, the hydrophobically modified SiC sample exhibits a significant characteristic response peak for fluorine (F) in its XPS full spectrum, indicating a substantial increase in the fluorine signal intensity. This phenomenon stems from the successful grafting of fluorine-containing hydrophobic functional groups onto the SiC surface by the perfluorodecyltriethoxysilane modifier, achieving effective introduction of fluorine. In summary, these characterization results fully confirm the successful hydrophobic modification of the SiC powder surface.

[0071] 3. Comparison of PU, MPU, SPU, and MSPU prepared in Comparative Examples 1-5 3:1 MSPU 1:1 The coating samples underwent SEM microstructure analysis and static water contact angle testing; the results are shown in the figure. Figure 7-8 .

[0072] Depend on Figure 7 (a) The results show that there are a large number of micron-sized pores inside the pure PU coating, which are inherent structural defects generated during the curing process of polyurethane. These pores are very easy to become channels for the penetration of corrosive media, which greatly reduces the barrier and anti-corrosion performance of the coating.

[0073] Depend on Figure 7 (b) The results show that the cross section of the MPU coating with single MXene filler can clearly observe a typical two-dimensional sheet structure. Corresponding to the MXene nanosheet filler, the sheets show a slight stacking phenomenon, which reflects the dispersion characteristics of single MXene filler in polyurethane matrix.

[0074] Depend on Figure 7 (c) The results show that the filler particles in the SPU coating with single-doped hydrophobic modified SiC filler are uniformly dispersed, the pore size of the coating is significantly reduced, and the pore distribution is more regular. The hydrophobic modified SiC can effectively fill the pores inside the polyurethane resin, and the filler is tightly bonded to the matrix interface, which effectively optimizes the basic microstructure of the coating.

[0075] Depend on Figure 7 (d) Figure 7 (e) The results show that MSPU with different formulation ratios... 3:1 With MSPU 1:1 The composite coating achieves an interwoven distribution of MXene sheets and hydrophobically modified SiC particles, constructing a three-dimensional barrier structure; among which MSPU 1:1 The coating exhibits the densest microstructure, with the fewest internal pores of uniform size and no obvious filler agglomeration or structural defects. Analysis shows that hydrophobic modification of SiC significantly improves the interfacial compatibility between the filler and the polyurethane matrix, suppresses filler agglomeration defects, and the synergistic combination of MXene and hydrophobically modified SiC effectively optimizes the coating's microstructure and dense internal network, significantly enhancing the physical density and long-term corrosion barrier properties of the composite coating.

[0076] Depend on Figure 8 The results show that the pure polyurethane (PU) coating contains polar groups such as -NH and -C=O in the urethane bonds. These polar groups easily adsorb water molecules, giving the pure PU coating a certain degree of hydrophilicity, making it difficult to maintain excellent waterproof barrier and anti-corrosion performance in humid and corrosive environments. Test data shows that the water contact angle of the pure PU coating is approximately 54.6°. The MPU coating prepared by introducing a single MXene filler has a water contact angle increased to 58.2°, with a slight improvement in surface hydrophobicity. This is because the two-dimensional lamellar structure of MXene can increase the surface roughness of the coating, effectively inhibiting the spread and penetration of water molecules on the coating surface. The SPU coating prepared by introducing only hydrophobically modified SiC has a water contact angle of approximately 53.5°, which is basically close to that of the pure PU coating, indicating that the single hydrophobically modified SiC filler has a weak regulatory effect on the wettability of the coating surface in this system. After MXene and hydrophobically modified SiC are combined, the MSPU... 3:1 Coating and MSPU 1:1 The water contact angles of the coatings were 53.9° and 55.4°, respectively, with MSPU... 1:1 The coating has slightly better hydrophobicity than pure PU coating, while MSPU... 3:1 The coating has performance that is basically the same as that of pure PU coating.

[0077] 4. Analysis of the electrochemical polarization performance of the composite coating To quantitatively characterize the corrosion resistance of each coating sample, Tafel dynamic polarization curves were tested on the bare steel and each group of coated samples. The results are shown in [Figure number missing]. Figure 9 The corrosion potential (E) reflects the ease with which corrosion occurs, while the corrosion current density (i) reflects the corrosion reaction rate. The more positive the potential and the lower the current density, the better the corrosion resistance.

[0078] Depend on Figure 9 The results show that there are significant differences in corrosion potential (E) and corrosion current density (i) among the samples, and the gradient variation of corrosion resistance is obvious. Among them, Q235 bare steel has the most negative corrosion potential and the largest corrosion current density, with E = -835 mV and i = 2.19 × 10⁻⁶ A·cm⁻¹. -2 It is highly sensitive to corrosive media and has the worst corrosion resistance. After coating with a pure polyurethane coating, the corrosion resistance of the substrate is significantly improved, the corrosion potential of the coating shifts positively to -588 mV, and the corrosion current density decreases to 1.71 × 10 A·cm. -2The corrosion current density decreased by two orders of magnitude, proving that the polyurethane resin matrix can effectively block the intrusion of corrosive media and has a good protective effect on carbon steel substrates. Both the MPU coating with single MXene doping and the SPU coating with single hydrophobic modified SiC doping showed a slight positive shift in corrosion potential compared to the pure PU coating, but the corrosion current density did not show a significant decrease. This indicates that single filler modification has a limited effect on improving the anti-corrosion performance of the coating, and is prone to forming new media penetration channels due to uneven filler dispersion and residual interface defects, making it difficult to achieve long-term anti-corrosion protection. After MXene and hydrophobic modified SiC were combined and modified, the MSPU... 3:1 With MSPU 1:1 The corrosion current density of the composite coating was significantly lower than that of the pure PU coating, demonstrating that the dual-filler synergistic system can combine the two-dimensional lamellar barrier effect of MXene with the interstitial reinforcement advantage of hydrophobically modified SiC particles, complementarily optimizing the coating microstructure, eliminating porosity defects, and significantly improving the coating density and corrosion barrier performance. 3:1 >MPU>SPU>MSPU 1:1 >PU>Bare; Corrosion current density i from largest to smallest is Bare>PU>SPU>MPU>MSPU 3:1 MSPU 1:1 The above test results show that the synergistic effect of dual filler compounding is significantly better than that of single filler modification, and the MSPU series composite coatings prepared by this invention have excellent corrosion resistance and protection performance.

[0079] 5. Electrochemical impedance performance analysis of composite coating After immersing each group of coated samples in a 0.5 wt% sodium chloride solution for 48 h, electrochemical impedance spectroscopy (EIS) was performed. The obtained Nyquist, Bode impedance, and Bode phase spectra are shown below. Figure 10 The capacitive arc radius, low-frequency impedance modulus, and characteristic phase angle are the core indicators for evaluating the density and long-term corrosion resistance of the coating. The larger the capacitive arc, the higher the low-frequency impedance value, and the larger the phase angle, the better the coating's shielding and barrier capabilities and structural stability.

[0080] Depend on Figure 10 (a) The Nyquist plot results show that the capacitive arc radius of each coated sample exhibits a significant gradient change, with the trend being as follows: MSPU 3:1 MSPU 1:1The order of SPU > MPU > PU shows a high degree of agreement with the Tafel polarization curve test results. The pure PU coating exhibits the smallest capacitive arc radius. This is because the cured pure polyurethane coating contains numerous micron-sized pores and microscopic defects, providing convenient channels for the penetration and diffusion of corrosive media, resulting in weak barrier protection. By introducing MXene two-dimensional lamellar fillers and hydrophobically modified SiC particles, the dual fillers can construct a dense physical shielding network within the polyurethane matrix, effectively extending the diffusion and penetration path of corrosive media and significantly improving the coating's impedance and corrosion resistance stability. Among these, MSPU... 3:1 With MSPU 1:1 The composite coating exhibits excellent electrochemical stability and long-term corrosion resistance.

[0081] Depend on Figure 10 (b) Bode impedance spectroscopy results show that the impedance modulus |Z| at 0.01 Hz in the low-frequency region directly reflects the coating's ability to block corrosive media; the larger the modulus, the better the coating's protective performance. The low-frequency impedance moduli of each group of samples are as follows: SPU (4882.6 Ω·cm). 2 )>PU(4311 Ω·cm 2 MSPU 1:1 (3774.6 Ω·cm 2 MSPU 3:1 (2814.1 Ω·cm 2 )>MPU(2592.7Ω·cm 2 The SPU coating has the highest low-frequency impedance modulus, which is presumably due to external noise interference in the low-frequency test environment. This is a normal fluctuation in electrochemical testing and does not affect the determination of the overall coating's anti-corrosion performance variation.

[0082] Depend on Figure 10 (c) Bode phase spectrum results show that the phase angle at 10 Hz is positively correlated with the corrosion resistance of the coating; the larger the phase angle, the better the coating's density and corrosion resistance. The phase angles of each group of samples are as follows: MSPU 3:1 (31.47°)>MSPU 1:1The order of change (30.72°) > SPU (18.99°) > MPU (17.36°) > PU (2.39°) is completely consistent with the Nyquist spectrum and Tafel polarization test results. Pure PU coatings, due to inherent structural defects such as micropores and microcracks, cannot effectively block the penetration of corrosive media, resulting in the weakest corrosion resistance. The introduction of MXene and hydrophobically modified SiC functional fillers effectively fills the microscopic defects of the coating, improves the interface between the filler and the matrix, significantly enhances the coating's density, increases the phase angle peak width, and shifts it towards lower frequencies. This fully demonstrates that the synergistic modification of the dual fillers can significantly optimize the coating's microstructure and strengthen the shielding and barrier properties and long-term corrosion resistance of the composite coating.

[0083] This invention is not limited to the specific embodiments described above. Any modifications made by those skilled in the art based on the above concept without creative effort are within the scope of protection of this invention.

Claims

1. A method for preparing an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating, characterized in that, Includes the following steps: S1. Hydrophobic modification of SiC powder was carried out by perfluorodecyltriethoxysilane, and fluorinated hydrophobic groups were grafted onto the surface of SiC powder to prepare hydrophobic modified SiC powder. S2. Pre-treat the steel substrate, then mix and disperse MXene powder with the hydrophobic modified SiC powder, and then mix it evenly with waterborne polyurethane component A, dispersant and waterborne polyurethane component B curing agent to obtain a composite coating slurry; coat the composite coating slurry onto the surface of the pre-treated substrate, and then cure it in stages to obtain an MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating.

2. The method for preparing the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 1, characterized in that, In step S1, the mass ratio of the SiC powder to perfluorodecyltriethoxysilane is 1:0.5-1.

3. The preparation method of the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 1, characterized in that, In step S1, the reaction temperature for the hydrophobic modification treatment is 45–55°C, and the reaction time is 25–35 min.

4. The method for preparing the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 1, characterized in that, The steel substrate is Q235 steel. The substrate pretreatment process is as follows: after grinding the steel surface with 600-grit sandpaper to remove rust and dirt, it is immersed in NaOH solution for 1-2 hours to complete the substrate surface pretreatment.

5. The method for preparing the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 1, characterized in that, In step S2, the segmented curing molding process is as follows: curing at room temperature for 20–28 h, followed by constant temperature curing at 55–65℃ for 10–14 h.

6. The method for preparing the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 1, characterized in that, The preparation process of the composite coating slurry is as follows: MXene powder and hydrophobically modified SiC powder are mixed, and anhydrous ethanol is added and ultrasonically dispersed for 25-35 min; then waterborne polyurethane component A, dispersant and waterborne polyurethane component B curing agent are added in sequence. After each component is added, the mixture is stirred for 10-20 min and mixed evenly to obtain the composite coating slurry.

7. The method for preparing the MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating according to claim 6, characterized in that, The mass ratio of MXene powder to hydrophobically modified SiC powder is 1:2 to 1:

5.

8. An MXene / hydrophobic modified SiC synergistic reinforced polyurethane anti-corrosion composite coating prepared by the preparation method according to any one of claims 1-7.

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