Super-hydrophobic composite coating and preparation method thereof

Abstract

The invention belongs to the technical field of metal anticorrosive coating materials, and particularly relates to a super-hydrophobic composite coating and a preparation method thereof. According to the invention, MoS2 is used as a skeleton, CeO2 nanoparticles are uniformly loaded on the surface of a MoS2 two-dimensional layered structure, polydopamine is used as a connecting agent to form a stable Ce-MoS2 composite filler, and an active and passive protective layer with the Ce-MoS2 composite filler is constructed on the surface of a matrix and is used as a bottom layer. And then, forming a hydrophobic coating containing modified SiO2 on the bottom layer to serve as a surface layer, so as to obtain the super-hydrophobic composite coating with double protection mechanisms. According to the coating, the active corrosion inhibition function of CeO2 and the physical shielding effect of MoS2 are combined, meanwhile, hydrophobic SiO2 nano-particles are introduced into the surface layer, the hydrophobic performance of the surface is further enhanced, and therefore the technical problems that a traditional coating is prone to corrosion at the defect position and a corrosive medium is prone to permeation, and consequently the protection effect is remarkably reduced are effectively solved.

Description

Technical Field

[0001] This invention belongs to the technical field of metal anti-corrosion coating materials, specifically relating to a superhydrophobic composite coating and its preparation method. Background Technology

[0002] In the field of corrosion protection, epoxy resin coatings are widely used on metal surfaces due to their excellent protective properties. However, pure epoxy resin coatings have some drawbacks, such as the micropores formed during curing, which result in insufficient mechanical strength and a tendency to crack or penetrate in harsh environments, thus limiting their application range.

[0003] To address these issues, researchers have attempted to introduce organic or inorganic fillers, such as graphene, montmorillonite, polyaniline, and mica flakes, into epoxy resins to enhance the barrier properties, corrosion resistance, and mechanical properties of the coating. Among these, the two-dimensional transition metal disulfide MoS2, due to its layered structure, hydrophobicity, and antioxidant properties, has been shown to effectively enhance the corrosion resistance and mechanical strength of the coating, and its high band gap avoids the microgalvanic corrosion problems that may be caused by fillers such as graphene. Furthermore, cerium dioxide, as a highly efficient corrosion inhibitor, can release Ce in the corroded area. 3+ and Ce 4+ Ions are formed to create a passivation film, achieving active protection of the metal substrate.

[0004] Furthermore, superhydrophobic coatings with extreme hydrophobic properties, due to their extremely low surface energy, can effectively block the penetration of moisture and corrosive media, significantly improving the coating's corrosion resistance and durability. However, coatings relying solely on physical barriers or a single superhydrophobic mechanism are still insufficient to cope with complex and varied operating environments, especially when mechanical damage or localized defects are present, their protective effect will significantly decrease. Summary of the Invention

[0005] To address the technical problem that existing coatings have limited application environments, especially when mechanical damage or local defects are present, their protective effect will significantly decrease, this invention provides a superhydrophobic composite coating and its preparation method.

[0006] This invention uses MoS2 as a framework, uniformly loading CeO2 nanoparticles onto the surface of a two-dimensional layered MoS2 structure, and utilizing polydopamine as a binder to form a stable Ce-MoS2 composite filler. This forms an active and passive protective layer on the substrate surface, consisting of a Ce-MoS2 composite filler, as the bottom layer. Then, a hydrophobic coating containing modified SiO2 is formed on the bottom layer as the top layer, resulting in a superhydrophobic composite coating with a dual protective mechanism. This coating combines the active corrosion inhibition function of CeO2 with the physical shielding effect of MoS2. Furthermore, the introduction of hydrophobic SiO2 nanoparticles into the surface layer further enhances the surface's hydrophobic properties, effectively solving the technical problems of traditional coatings being prone to corrosion at defects and easily penetrated by corrosive media, leading to a significant decrease in protective effectiveness.

[0007] The first objective of this invention is to provide a superhydrophobic composite coating, which is a two-layer structure coating consisting of a bottom layer and a top layer sequentially coated on the surface of a substrate; the bottom layer is an epoxy resin coating containing Ce-MoS2 filler, wherein the Ce-MoS2 filler is formed by loading CeO2 nanoparticles onto the surface of a two-dimensional layered MoS2; the top layer is an epoxy resin superhydrophobic coating containing modified SiO2, wherein the modified SiO2 is SiO2 nanoparticles modified with siloxane.

[0008] Preferably, the Ce-MoS2 filler accounts for 0.5% to 1.5% of the mass of the epoxy resin in the substrate. Insufficient Ce-MoS2 composite filler content cannot form a sufficient physical barrier effect, resulting in weak barrier performance; excessive addition of Ce-MoS2 composite filler can easily lead to particle aggregation, forming microscopic defects in the coating, thereby weakening the anti-corrosion performance of the coating.

[0009] Preferably, the modified SiO2 accounts for 30% to 70% of the mass of the epoxy resin in the surface layer. By adding modified SiO2 to the epoxy resin, a highly continuous and compact micro / nano-scale rough structure is formed. This structure can trap more air, forming an effective solid-liquid-gas three-phase interface. Combined with the low surface energy properties imparted by the modified SiO2, this achieves superhydrophobicity in the composite coating. If the amount of modified SiO2 added is too low, the number of hydrophobic SiO2 nanoparticles is insufficient, resulting in a sparse micro / nano structure on the surface, making it difficult to achieve superhydrophobicity. Furthermore, the epoxy resin matrix dominates, and the coating easily exposes the epoxy matrix after wear, thus losing its hydrophobic properties. If the amount of modified SiO2 added is too high, the coating and bonding effect of the epoxy resin matrix weakens, and particles are more likely to detach during wear, damaging the micro / nano structure on the surface and causing a rapid decrease in hydrophobicity.

[0010] Preferably, the thickness of the superhydrophobic composite coating is 90μm to 110μm.

[0011] The second objective of this invention is to provide a method for preparing a superhydrophobic composite coating, comprising the following steps: MoS2, Ce source, and buffer solution are mixed, and dopamine hydrochloride is added to induce a self-polymerization reaction, which uniformly loads CeO2 onto the two-dimensional layered structure surface of MoS2 to obtain Ce-MoS2 filler. Ce-MoS2 filler, resin, curing agent, and first solvent are mixed uniformly and coated onto the substrate. After curing, the bottom layer is obtained. Modified SiO2, resin, curing agent, and second solvent are mixed uniformly and coated onto the bottom layer. After curing, the top layer is formed to obtain a superhydrophobic composite coating.

[0012] The preferred method for preparing modified SiO2 is as follows: SiO2 was dispersed in an ammonia solution, siloxane was added, the mixture was stirred and reacted, and the mixture was centrifuged to obtain modified SiO2.

[0013] Preferably, the ratio of SiO2 to modifier is 1g:2mL.

[0014] Preferably, the mass ratio of MoS2 to Ce source is 5:8.

[0015] Preferably, the mass ratio of MoS2 to dopamine hydrochloride is 1:1.

[0016] Preferably, the temperature of the self-polymerization reaction is 40℃~50℃ and the time is 24h.

[0017] Preferably, the Ce source is cerium nitrate, cerium acetate, or CeO2.

[0018] Preferably, the first solvent is xylene and n-butanol, with a mass ratio of xylene to n-butanol of 7:3.

[0019] Preferably, the second solvent is ethyl acetate.

[0020] Preferably, the resin is epoxy resin. Compared with the prior art, the present invention has the following technical effects: 1. This invention uses MoS2 as a framework, uniformly loading CeO2 nanoparticles onto the surface of a two-dimensional layered structure of MoS2, and utilizing polydopamine as a binder to form a stable Ce-MoS2 composite filler. This forms an active and passive protective layer on the substrate surface, consisting of the Ce-MoS2 composite filler, as the bottom layer. Then, a hydrophobic coating containing modified SiO2 is formed on the bottom layer as the top layer, resulting in a superhydrophobic composite coating with a dual protective mechanism. Through the active corrosion inhibition function of CeO2 and the physical shielding effect of MoS2, as well as the further enhancement of the surface's hydrophobic properties by the modified SiO2 hydrophobic coating, the technical problem of traditional coatings being prone to corrosion at defects and easily penetrated by corrosive media, leading to a significant decrease in protective effect, is effectively solved.

[0021] 2. This invention utilizes the two-dimensional lamellar structure of MoS2 to create a labyrinth effect in the coating, significantly extending and torturing the penetration path of corrosive media, thus achieving physical barrier. Simultaneously, when a small amount of media penetrates to the metal interface, CeO2 is used to target and release Ce. 3+ A passivation film is formed at metal defects, achieving active corrosion inhibition. The physical barrier properties of the coating are synergistically enhanced by MoS2 and firmly bonded CeO2 particles. Furthermore, the superhydrophobic barrier of the surface effectively prevents droplet adhesion and penetration, reducing the intrusion of corrosive media at its source.

[0022] 3. After soaking in a 3.5 wt.% NaCl solution for 45 days, the low-frequency impedance modulus of the superhydrophobic composite coating prepared in this invention remains at 5.85 × 10⁻⁶. 10 Ω·cm 2 The above figures are four orders of magnitude higher than those of pure epoxy coatings. After 480 hours of neutral salt spray testing with 5wt.% NaCl, no significant rust was observed at the scratched areas. Furthermore, due to the strong fixation of the modified SiO2 particles by the epoxy resin, this superhydrophobic surface maintains its superhydrophobic properties even after 500cm of sandpaper abrasion, overcoming the poor mechanical stability of traditional superhydrophobic coatings. Moreover, the superhydrophobic surface can automatically roll off contaminant droplets, keeping the surface clean and further extending the coating's lifespan. Attached Figure Description

[0023] Figure 1 The image shows the FTIR spectra of SiO2 and modified SiO2 nanoparticles.

[0024] Figure 2 In the image, (a) shows the XRD patterns of MoS2, CeO2, and Ce-MoS2 packings; (b) shows a magnified view of a local area in (a).

[0025] Figure 3 In the image, (a) is the SEM image of MoS2; (b) is the SEM image of Ce-MoS2 filler; (c) is the corresponding Mo element mapping result; (d) is the corresponding S element mapping result; (e) is the corresponding Ce element mapping result; and (f) is the corresponding C element mapping result.

[0026] Figure 4 (a1) Optical image, (a2) CA image and (a3) ​​SEM image of EP coating; (b1) Optical image, (b2) CA image and (b3) SEM image of SH-SiO2 / EP@Ce-MoS2 coating.

[0027] Figure 5 CA curve of the superhydrophobic composite coating prepared in Example 2.

[0028] Figure 6These are SEM images of the superhydrophobic composite coatings prepared with different modified SiO2 contents in Example 2. Specifically, (a1) is a SEM image of the superhydrophobic composite coating prepared with 30% modified SiO2 at a scale of 100 μm, with the inset showing the coating's CA (cathode). (a2) is a SEM image of the superhydrophobic composite coating prepared with 30% modified SiO2 at a scale of 3 μm; (b1) is a SEM image of the superhydrophobic composite coating prepared with 40% modified SiO2 at a scale of 100 μm, with the inset showing the coating's CA; (b2) is a SEM image of the superhydrophobic composite coating prepared with 40% modified SiO2 at a scale of 3 μm; (c1) is a SEM image of the superhydrophobic composite coating prepared with 50% modified SiO2 at a scale of 100 μm, with the inset showing the coating's CA; (c2) is... SEM image of the superhydrophobic composite coating prepared with 50% modified SiO2 at the 3 μm scale; (d1) SEM image of the superhydrophobic composite coating prepared with 60% modified SiO2 at the 100 μm scale, with the inset showing the coating's CA; (d2) SEM image of the superhydrophobic composite coating prepared with 60% modified SiO2 at the 3 μm scale; (e1) SEM image of the superhydrophobic composite coating prepared with 70% modified SiO2 at the 100 μm scale, with the inset showing the coating's CA; (e2) SEM image of the superhydrophobic composite coating prepared with 70% hydrophobic SiO2 nanoparticles at the 3 μm scale; (f) Dynamic contact process of water droplets on the composite coating.

[0029] Figure 7 The trend of hydrophobic properties of the coating under different wear distances is shown; (a) is the superhydrophobic composite coating prepared with 60% modified SiO2; (b) is the superhydrophobic composite coating prepared with 70% modified SiO2.

[0030] Figure 8 In the image, (a) is an SEM image of the superhydrophobic composite coating prepared in Example 1; (b) is an SEM image after sandpaper abrasion of 500 cm.

[0031] Figure 9 The trend of changes in the hydrophobic properties of the coating under different peeling cycles is shown.

[0032] Figure 10 Schematic diagram of the self-cleaning performance of (a) EP and (b) SH-SiO2 / EP@Ce-MoS2 superhydrophobic composite coatings.

[0033] Figure 11The antifouling performance of the superhydrophobic composite coating prepared in Example 1 was tested against different liquids; wherein, (a) is deionized water stained with methylene blue, (b) Coca-Cola stained with methylene blue, (c) milk stained with methylene blue, (d) coffee stained with methylene blue, (e) tea stained with methylene blue, and (f) fruit juice stained with methylene blue.

[0034] Figure 12 EIS plots of 0.5Ce-MoS2 / EP, 1Ce-MoS2 / EP, 1.5Ce-MoS2 / EP, and SH-SiO2 / EP@Ce-MoS2 during a 45-day immersion period are shown. Among them, (a1) is the Bode plot of 0.5Ce-MoS2 / EP; (a2) is the Nyquest plot of 0.5Ce-MoS2 / EP; (b1) is the Bode plot of 1Ce-MoS2 / EP; (b2) is the Nyquest plot of 1Ce-MoS2 / EP; (c1) is the Bode plot of 1.5Ce-MoS2 / EP; (c2) is the Nyquest plot of 1Ce-MoS2 / EP; (d1) is the Bode plot of SH-SiO2 / EP@Ce-MoS2; and (d2) is the Nyquest plot of SH-SiO2 / EP@Ce-MoS2.

[0035] Figure 13 The low-frequency impedance values ​​|Z| of each coating during the 45-day immersion period. 0.01Hz Trends over time.

[0036] Figure 14 This is the equivalent circuit used to fit EIS data.

[0037] Figure 15 Optical images of each coating sample after 480h salt spray corrosion test; where (a) is 0.5Ce-MoS2 / EP; (b) is 1Ce-MoS2 / EP; (c) is 1.5Ce-MoS2 / EP; and (d) is SH-SiO2 / EP@Ce-MoS2.

[0038] Figure 16 The XPS spectra of the corrosion products are shown; where (a) is the full spectrum and (b) is Ce3d.

[0039] Figure 17 This is a diagram of the corrosion mechanism. Detailed Implementation

[0040] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0041] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0042] Example 1 A method for preparing a superhydrophobic composite coating includes the following steps: Step 1: Preparation of Ce-MoS2 composite filler: Weigh 0.24 g of tris(hydroxymethyl)aminomethane and add it to 200 ml of deionized water. Stir until completely dissolved and adjust the pH to 8.5 with 0.1 M dilute hydrochloric acid solution to obtain Tris-HCl buffer solution.

[0043] Weigh 0.5 g of MoS2 and 0.8 g of CeO2 and add them to Tris-HCl buffer solution. Stir ultrasonically for 30 min to disperse evenly. Then add 0.5 g of dopamine hydrochloride and stir at 45 °C for 24 h. Collect by centrifugation and wash three times with deionized water and anhydrous ethanol. Dry the obtained product under vacuum at 60 °C for 24 h to obtain Ce-MoS2 filler.

[0044] Step 2: Preparation of modified SiO2: 2.5 g of nano-SiO2 was weighed and added to 25 mL of ammonia solution with pH=9. The mixture was stirred for 30 min to obtain a SiO2 suspension. 5 mL of dodecyltrimethoxysilane was added to 50 mL of anhydrous ethanol and stirred for 30 min. Then, the mixture was added to the SiO2 suspension and magnetically stirred for 12 h. The mixture was centrifuged to collect the precipitate, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C for 12 h to obtain modified SiO2.

[0045] A Q235 steel plate with dimensions of 150mm×70mm×1mm was sanded sequentially using 400-grit, 800-grit, and 1200-grit sandpaper, and then cleaned with alcohol and thoroughly dried before use.

[0046] Step 3: Prepare an epoxy resin coating containing Ce-MoS2 filler: 4g of E44 epoxy resin was added to a mixed solvent of 4g xylene and n-butanol to obtain a mixture; wherein the mass ratio of xylene to n-butanol was 7:3. The mixture was magnetically stirred for 30 minutes to ensure that the epoxy resin was fully dissolved in the mixed solvent.

[0047] Ce-MoS2 filler was added to the mixture, and the mixture was ultrasonicated and stirred for 30 minutes to ensure uniform dispersion of the filler in the epoxy resin. Polyamide 650 curing agent was then added and stirred for 10 minutes to obtain an epoxy mixture containing Ce-MoS2 filler. The mass of Ce-MoS2 filler accounted for 1.0% of the mass of epoxy resin.

[0048] A Q235 steel plate with dimensions of 150mm×70mm×1mm was sanded sequentially using 400-grit, 800-grit, and 1200-grit sandpaper, and then cleaned with alcohol and thoroughly dried before use.

[0049] Using a polished and cleaned steel plate as the substrate, an epoxy mixture containing Ce-MoS2 filler is evenly sprayed onto the substrate using a spray gun. The distance between the spray gun and the substrate is controlled at 15cm to 20cm. After coating, the epoxy resin coating containing Ce-MoS2 filler is cured at 50℃ for 10h to obtain an epoxy resin coating as the base layer.

[0050] Step 4: Prepare the superhydrophobic composite coating: 2g of epoxy resin E51 was dissolved in 20mL of ethyl acetate, then modified SiO2 was added, and the mixture was ultrasonically stirred for 30min to disperse it evenly. 0.6g of polyetheramine D230 was added and stirred for 10min to obtain a mixture. The mass of modified SiO2 accounted for 60% of the mass of epoxy resin in the surface layer.

[0051] The mixture was uniformly sprayed onto the cured base layer using the same spraying method, and then cured at 60°C for another 8 hours to obtain a superhydrophobic composite coating, denoted as SH-SiO2 / EP@Ce-MoS2, with the coating thickness controlled at 100±10μm.

[0052] Example 2 A method for preparing a superhydrophobic composite coating is basically the same as that in Example 1, except that the content of modified SiO2 added is different.

[0053] Table 1. Superhydrophobic composite coatings prepared with different modified SiO2 contents. Note: "Modified SiO2 content" indicates the percentage of modified SiO2 by mass in the epoxy resin.

[0054] Example 3 A method for preparing a superhydrophobic composite coating is basically the same as that in Example 1, except that the mass of Ce-MoS2 filler accounts for 0.5% of the mass of epoxy resin.

[0055] Example 4 A method for preparing a superhydrophobic composite coating is basically the same as that in Example 1, except that the mass of Ce-MoS2 filler accounts for 1.5% of the mass of epoxy resin.

[0056] Comparative Example 1 A method for preparing a coating differs from that in Example 1 as follows: An epoxy resin coating containing Ce-MoS2 filler is applied to a substrate, wherein the mass of Ce-MoS2 filler accounts for 0.5% of the mass of epoxy resin; denoted as 0.5Ce-MoS2 / EP.

[0057] Comparative Example 2 A method for preparing a coating differs from that in Example 1 as follows: An epoxy resin coating containing Ce-MoS2 filler is applied to the substrate; denoted as 1Ce-MoS2 / EP.

[0058] Comparative Example 3 A method for preparing a coating differs from that in Example 1 as follows: An epoxy resin coating containing Ce-MoS2 filler is applied to a substrate, wherein the amount of Ce-MoS2 filler added accounts for 1.5% of the mass of the epoxy resin; denoted as 1.5Ce-MoS2 / EP.

[0059] 1. Infrared testing.

[0060] like Figure 1 As shown, the FTIR spectrum indicates that DTMS-modified SiO2 at 2923 cm⁻¹ -1 and 2852cm -1 The appearance of new peaks corresponds to the CH stretching of -CH2 and -CH3, respectively, indicating that the alkyl chain of DTMS was successfully modified onto SiO2. To visually demonstrate the effect of DTMS modification on the hydrophobicity of SiO2, SiO2 and DTMS-modified SiO2 were added to deionized water, respectively. After soaking for 10 days, SiO2 sank to the bottom, while the hydrophobically modified SH-SiO2 remained floating in the deionized water.

[0061] 2. X-ray diffraction analysis.

[0062] like Figure 2 As shown, the XRD pattern of CeO2 shows diffraction peaks at 28.6°, 33.1°, 47.5°, and 56.4°, corresponding to the (111), (200), (220), and (311) crystal planes of CeO2 with MoS2, CeO2, and Ce-MoS2 fillers, respectively. The XRD pattern of MoS2 shows diffraction peaks at 14.4°, 32.7°, 39.5°, and 49.8°, corresponding to the (002), (100), (103), and (105) crystal planes of MoS2, respectively. The XRD pattern of Ce-MoS2 filler shows a diffraction peak at 14.4° corresponding to the (002) crystal plane of MoS2, but the intensity of this peak is much lower than that of MoS2, indicating that MoS2 is encapsulated by PDA, reducing the diffraction intensity. Meanwhile, the XRD pattern of Ce-MoS2 filler also showed diffraction peaks at 28.6°, 33.1°, 47.5° and 56.4°, which are consistent with the characteristic peaks of CeO2. This proves that CeO2 nanoparticles were successfully loaded onto MoS2.

[0063] 3. Scanning electron microscopy test and hydrophobicity test.

[0064] like Figure 3 As shown in (a), the SEM image of MoS2 shows that the original MoS2 filler has a clearly visible layered structure of 1μm to 5μm and a smooth surface. This layered arrangement provides a uniform and continuous physical barrier for the coating, effectively blocking the penetration of corrosive media, which is the key factor for its excellent barrier performance in anti-corrosion coatings. Figure 3 Image (b) shows a SEM image of the Ce-MoS2 filler surface morphology, revealing a large number of nanoparticles on the MoS2 surface. EDS analysis shows that Mo, S, Ce, and C elements are uniformly distributed in the sample, with the uniform distribution of C mainly attributed to the self-polymerization of dopamine. These results further demonstrate the successful loading of CeO2 onto the MoS2 surface and reveal the structural characteristics of the modified Ce-MoS2 filler.

[0065] like Figure 4 As shown in (a1) and (a2), water droplets exhibit significant hydrophilicity on the pure epoxy resin surface, with a water contact angle of 71.4°. After spraying a superhydrophobic coating, as... Figure 4 As shown in (b1) and (b2), the water droplets exhibit a distinct spherical shape on the coating surface, with a water contact angle of 158.5°, achieving superhydrophobicity. (Comparison) Figure 4 In (a3) ​​and (b3), the EP coating surface is smooth and flat, while after spraying the superhydrophobic coating, a rough micro / nano structure is formed on the surface. The synergistic effect of these micro / nano structures and hydrophobic siloxane groups endows the coating with significant superhydrophobicity.

[0066] Modified SiO2 nanoparticles play a dominant role in determining the micro / nano structure and low surface energy properties of the coating. Therefore, to achieve a synergistic effect and obtain ideal surface properties, it is necessary to rationally control the ratio of modified SiO2 nanoparticles to epoxy adhesive. Figure 5 As shown, the hydrophobicity of the coating increases with the increasing proportion of modified SiO2.

[0067] like Figure 6 As shown, by analyzing the SEM images and magnified views of the composite coating, the mechanism by which the modified SiO2 content affects the surface morphology and superhydrophobic properties of the coating can be revealed in depth. Low content stage (30%): From the macroscopic observation in (a1) of section 6, the coating surface is relatively smooth with sparse particle distribution. Magnified view... Figure 6Figure (a2) shows that the modified SiO2 nanoparticles cannot form a continuous micro / nano structure, and the surface roughness is significantly insufficient. This results in a lack of an air buffer layer when the coating comes into contact with droplets, with a contact angle of 145.4° and poor hydrophobic properties. At 40% content: Figure (b1) in 6 shows that the number of particles increases, and the surface roughness begins to improve, but a complete micro / nano network structure is still not formed. At 50% content: Macroscopic... Figure 6 (c1) shows a significant increase in the surface roughness of the coating, as indicated by local magnification. Figure 6 (c2) further reveals the formation of micro- and nano-scale rough structures between particles. This structure provides the foundation for superhydrophobic properties, increasing the water contact angle to 155.6° and exhibiting better hydrophobicity. 60% content: Figure 6 (d1) shows that the particles on the coating surface are uniformly distributed and have a stable morphology. (Magnification) Figure 6 The highly continuous and compact surface micro-nano structure of (d2) allows for the trapping of more air, forming an effective solid-liquid-gas three-phase interface. Combined with modified SiO2 nanoparticles, this imparts low surface energy to the coating, a key factor in achieving superhydrophobicity. Figure 6 As shown in (f), water droplets hardly adhere to the coating surface, with a contact angle as high as 158.5°, further enhancing the superhydrophobicity. When the modified SiO2 content is further increased to 70%, the hydrophobic properties of the superhydrophobic coating are not significantly improved. However, since a further decrease in the epoxy resin ratio will reduce the mechanical stability of the coating, the optimal addition amount of modified SiO2 is 60%, and this ratio is used in the subsequent preparation of the superhydrophobic composite coating.

[0068] 4. Mechanical stability analysis.

[0069] The mechanical stability of the coating was evaluated using sandpaper abrasion and tape peel tests. The amount of modified SiO2 added plays a crucial role in the mechanical stability of the superhydrophobic coating. When the amount of modified SiO2 added is low, the number of hydrophobic SiO2 particles is insufficient, resulting in a sparse micro / nano structure on the surface. The coating exhibits poor superhydrophobicity, with the contact angle failing to meet the superhydrophobic standard (>150°). The epoxy resin matrix becomes dominant, and after wear, the coating easily exposes the epoxy groups, thus losing its hydrophobic properties. The optimal addition amount of 60% shows improved abrasion resistance. Figure 7 As shown in (a), the contact angle gradually decreases with increasing friction distance, dropping from an initial 158.5° to 151.9° at 500cm, but still above 150°, indicating that the coating retains its superhydrophobicity. The roll-off angle gradually increases, reaching approximately 10.8° after 500cm, indicating that the coating's self-cleaning ability has not been completely lost. However, when the modified SiO2 ratio is too high (70%), the wear resistance is as follows... Figure 7As shown in (b), the contact angle decreases rapidly with increasing wear distance, indicating poor wear resistance. When the friction distance is 300 cm, its CA has dropped to 148.7°, losing its superhydrophobicity. SA rises to 13.6°, significantly affecting self-cleaning performance. This is because excessive hydrophobic silica particles weaken the coating and bonding effect of the epoxy resin matrix, making the particles more prone to detachment during wear, thus damaging the micro-nano structure of the surface and causing a rapid decrease in hydrophobicity.

[0070] This wear resistance is attributed to the synergistic effect of hydrophobic SiO2 and the epoxy resin matrix in an optimal ratio. The epoxy resin provides the mechanical strength of the coating, reducing the rapid destruction of the micro-nano structure during wear. The composite material formed by the hydrophobic silica particles and epoxy resin has a hierarchical micro-nano structure, exhibiting a gradual performance degradation during wear. Figure 8 As shown, even if the surface micron structure is partially destroyed during the wear process after 500 cm of wear, the underlying nanostructure will still be exposed, maintaining a high contact angle and a low roll-off angle.

[0071] In addition, a tape peel test was performed on the superhydrophobic composite coating prepared in Example 1 to evaluate its mechanical adhesion. A 100g weight was used to firmly adhere the tape to the coating surface, and then the tape was peeled off. This process was repeated every 5 cycles, measuring the CA and SA of the coating. Figure 9 As shown, with the increase of the number of tape peel tests, the CA of the coating continuously decreases while the SA continuously increases. After 40 tests, the CA of the coating is 150.3°, which remains above 150°, indicating that the coating has good mechanical adhesion.

[0072] 5. Analysis of self-cleaning and anti-fouling performance.

[0073] In real-world applications, dust, particles, and contaminants inevitably adhere to the coating surface, affecting its lifespan. Superhydrophobic coatings, with their self-cleaning properties, prevent long-term contaminant adhesion and reduce erosion of the material surface. For example... Figure 10 As shown in (a), the pure epoxy resin coating has poor hydrophobicity. After deionized water is added to the surface, mud and water mix to form a slurry that remains on the surface. The surface lacks self-cleaning function, and contaminants are difficult to remove. However, after deionized water is added to the surface of the superhydrophobic composite coating, as shown in (a), the surface exhibits good hydrophobicity. Figure 10 As shown in (b), sand particles on the surface are carried away and removed by water droplets, restoring the surface to cleanliness. This is due to the micro-nano-level rough structure of the superhydrophobic coating surface, combined with low surface energy material modification, resulting in a contact angle greater than 150° and a roll-off angle less than 10°. Water droplets cannot spread on the surface but form spherical droplets that roll easily. During the rolling process, the water droplets carry away surface dust or particles, thus removing surface contaminants. This property is significant in terms of anti-fouling, anti-corrosion, and cost-saving maintenance.

[0074] Figure 11 The antifouling performance of the superhydrophobic composite coating was demonstrated by immersing the coating in methylene blue-stained deionized water, Coca-Cola, milk, coffee, tea, and juice for a specified time. After removal, the coating surface remained dry and clean, with no contaminating liquid drips, effectively preventing the adhesion of contaminating liquids and exhibiting excellent antifouling capabilities. The antifouling mechanism of the superhydrophobic coating mainly stems from the synergistic effect of its surface micro / nano structure and low surface energy materials. This surface structure allows droplets to form a "ball-bead" effect on its surface, enabling them to quickly slide off and carry away surface contaminants, thus keeping the coating surface clean.

[0075] 6. Electrochemical impedance spectroscopy analysis.

[0076] Electrochemical impedance spectroscopy was performed on Ce-MoS2 coatings with different proportions to evaluate their corrosion resistance. Figure 12 As shown, the low-frequency impedance value reflects the coating's ability to block the penetration of corrosive media and is an important parameter for evaluating the coating's anti-corrosion performance. A higher impedance value indicates better barrier performance of the coating. Correspondingly, a larger semicircular diameter on the Nyquist plot indicates better barrier performance of the coating, making it more difficult for corrosive media to penetrate. Figure 12 As shown in (a1) and (a2), the initial low-frequency impedance modulus (0.5Ce-MoS2 / EP) at an addition of 0.5 wt.% is 1.05 × 10⁻⁶. 10 Ω·cm 2 After soaking for 45 days, the concentration decreased to 2.03 × 10⁻⁶. 9 Ω·cm 2 Its low-frequency impedance modulus decreases rapidly because insufficient filler content fails to create a sufficient physical barrier effect, resulting in weak barrier performance. When the addition amount is 1 wt.% (1Ce-MoS2 / EP), the initial impedance value is highest at 4.76 × 10⁻⁶. 10 Ω·cm 2 It remained at 1.26×10 after 45 days. 10 Ω·cm 2 Through Nyquist Figure 12 As shown in (b1) and (b2), the initial radius of 1 wt.% and the radius after 45 days of immersion are significantly greater than those of 0.5 wt.% and 1.5 wt.%, respectively. This indicates that the 1 wt.% filler content is uniformly distributed in the coating, effectively blocking corrosive media and significantly improving the coating's anti-corrosion performance. However, when the filler content is 1.5 wt.% (1.5Ce-MoS2 / EP), such as Figure 12 As shown in (c1) and (c2), although the low-frequency impedance modulus is still relatively high, the initial impedance value (1.27 × 10⁻⁶) is lower. 10 Ω·cm 2Coatings with less than 1 wt.% filler showed a faster decrease in impedance. This indicates that excessive filler addition led to particle agglomeration, creating microscopic defects in the coating and thus weakening its anti-corrosion performance. Therefore, the optimal anti-corrosion effect occurred at a filler content of 1 wt.%.

[0077] like Figure 13 As shown, the low-frequency impedance modulus value after 45 days of soaking is 1Ce-MoS2 / EP (1.26×10). 10 Ω·cm²)>0.5Ce-MoS2 / EP (2.03×10 9 Ω·cm 2 )>1.5Ce-MoS2 / EP (8.24×10 8 Ω·cm 2 The above indicates that 1 wt.% is the optimal addition amount. After spraying the superhydrophobic layer at the optimal addition amount, its initial low-frequency impedance modulus reached 7.11 × 10⁻⁶. 10 Ω·cm 2 This indicates that the superhydrophobic surface effectively reduces water adhesion and maintains a high impedance value by blocking the penetration of water and corrosive media. During the 45-day immersion process, its low-frequency impedance modulus remained consistently at 5.85 × 10⁻⁶. 10 Ω·cm 2 The above demonstrates that the superhydrophobic coating structure is stable and possesses excellent durability. Therefore, the introduction of the superhydrophobic coating significantly enhances the corrosion resistance of the entire system, which is the key reason for maintaining a high impedance value.

[0078] like Figure 14 As shown, the data is fitted. Where R... s R is the resistance of the solution. c and R ct These are the coating resistance and charge transfer resistance, respectively. The combined value of the coating resistance and charge transfer resistance characterizes the corrosion resistance of the coating protection system. c Q is the constant phase angle component of the coated capacitor. dl This represents the constant phase angle component of a double-layer capacitor.

[0079] The EIS data fitting results of each coating sample after immersion in 3.5 wt.% NaCl solution for 45 days are shown in Table 2. For the coating with 1 wt.% Ce-MoS2 addition, the R... c and R ctThe values ​​of the coatings with significantly higher addition amounts than those with 0.5 wt.% and 1.5 wt.% indicate that, at the optimal addition amount, the composite coating can form an effective physical barrier effect and inhibit corrosion of the metal surface through CeO2 corrosion inhibitor. At 0.5 wt.% addition, the physical barrier and active corrosion inhibition effects are insufficient, while at 1.5 wt.% addition, filler agglomeration leads to an increase in micro-defects in the coating. The R... c and R ct The value remained at 10 after 45 days. 10 Ω·cm 2 The above demonstrates that spraying a superhydrophobic coating significantly slows down the penetration of corrosive media and improves the durability of the coating.

[0080] Table 2. EIS data fitting results of each coated sample after immersion in 3.5 wt.% NaCl solution for 45 days. Note: Q C -Y0 represents the admittance parameter of a constant-phase element; Q C -n represents the diffusion index; Q dl -Y0 represents the admittance parameter of a double-layer constant-phase element; Q dl -n represents the dispersion index of a double-layer constant-phase element.

[0081] 7. Salt spray corrosion test.

[0082] The anti-corrosion performance of composite coating samples with different filler additions was further evaluated by conducting a 480-hour neutral salt spray test with 5 wt.% NaCl using a salt spray test chamber. Figure 15 As shown in (a), the corrosion products at the scratches of 0.5Ce-MoS2 / EP were significantly reduced compared to pure EP, and the corrosion range was narrowed. This indicates that the addition of a small amount of Ce-MoS2 improved the barrier performance of the coating, and CeO2 can release cerium ions (CeO2) at the scratches. 3+ / Ce 4+ Ce-MoS2 forms a passivation film on the metal substrate surface, inhibiting corrosion. However, insufficient filler content results in poor physical shielding and active release effects. Increasing the Ce-MoS2 content to 1 wt.% improves the effect. Figure 15 As shown in (b), corrosion at the 1Ce-MoS2 / EP scratch is further reduced, and the corrosion spread is significantly reduced. The filler maintains uniform dispersion in the coating while forming a more effective barrier effect, significantly reducing the penetration of corrosive media. Simultaneously, the higher CeO2 content provides a more effective active corrosion inhibition effect. Further increasing the addition amount to 1.5 wt.%, as shown in (b), further improvements are achieved. Figure 15 As shown in (c), excessive filler leads to uneven dispersion in the coating, resulting in new microscopic defects that affect the coating's corrosion resistance. Figure 15 As shown in (d), the corrosion at the scratch of SH-SiO2 / EP@Ce-MoS2 is the least severe, indicating that the superhydrophobic coating effectively reduces the adhesion and diffusion of corrosive media due to its micro-nano structure and low surface energy characteristics, and its synergistic effect with Ce-MoS2 further enhances the anti-corrosion performance of the coating.

[0083] To further investigate the corrosion inhibition mechanism of the coating in a corrosive environment, X-ray photoelectron spectroscopy analysis was performed on the corrosion products in the scratched area of ​​the 1 wt.% Ce-MoS2 composite coating after salt spray testing. Figure 16 As shown in (a), the full-spectrum test results indicate that Fe, O, C, and Ce elements were detected in the corrosion products, suggesting that the corrosion inhibition effect of cerium is evident in this region. The Ce3dXPS spectrum is shown below. Figure 16 As shown in (b) of the diagram, Ce 4+ The Ce3d3 / 2 and Ce3d5 / 2 peaks are located at 917.08 eV, 907.98 eV, 903.6 eV, and 888.58 eV, respectively. 3+ The Ce3d3 / 2 and Ce3d5 / 2 peaks are located at 901.38 eV, 898.79 eV, and 882.78 eV, respectively. These data indicate that cerium is present in the corrosion products primarily as Ce. 3+ and Ce 4+ The coexistence of the two oxidation states further confirms that a passivation film composed of Ce(OH)3 and CeO2 was formed on the surface of the scratch area. The two work together to form a stable corrosion inhibition barrier, indicating that Ce-MoS2 successfully played an active corrosion inhibition role at the scratch.

[0084] 8. Discussion on corrosion prevention mechanism.

[0085] like Figure 17 As shown in (b), compared with the pure epoxy resin coating, the addition of Ce-MoS2 significantly prolonged the penetration path of the corrosive medium and markedly enhanced the physical barrier effect of the coating. When a small amount of corrosive medium penetrated to the interface between the coating and the substrate, cerium played a corrosion-inhibiting role. 3+ It can undergo a passivation reaction with OH⁻ generated in the electrochemical corrosion cathode to form cerium hydroxide, which in turn is further converted into cerium oxide, thus forming a cerium oxide / cerium hydroxide passivation film on the surface of the metal substrate. This passivation film effectively prevents further erosion by the corrosive medium, and combined with two-dimensional MoS₂, it endows the coating with dual active and passive anti-corrosion functions.

[0086] Based on this, a superhydrophobic layer is further sprayed onto the coating surface to form an SH-SiO2 / EP@Ce-MoS2 composite coating, such as... Figure 17As shown in (c) above, this composite coating combines the excellent active and passive corrosion inhibition effects of Ce-MoS2 with the functionality of the superhydrophobic top layer. The superhydrophobic coating, through its unique micro / nano structure composed of hydrophobically modified nano-silica particles and E51 binder, exhibits excellent mechanical stability, effectively maintaining contact between the coating and the corrosive medium in accordance with the Cassie-Baxter model. This structure enables the coating to effectively prevent the adhesion and penetration of corrosive media on the surface for a long period, thereby significantly improving the coating's anti-corrosion performance and providing more durable protection.

[0087] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0088] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A superhydrophobic composite coating, characterized in that, The super-hydrophobic composite coating is a double-layer structure coating formed by coating a bottom layer and a surface layer on a substrate surface in sequence; The bottom layer is a resin coating containing Ce-MoS2 fillers, and the Ce-MoS2 fillers are formed by loading CeO2 nanoparticles on the surface of two-dimensional layered MoS2; The surface layer is a resin super-hydrophobic coating containing modified SiO2, and the modified SiO2 is SiO2 nanoparticles modified by siloxane; The mass of the Ce-MoS2 fillers accounts for 0.5%-1.5% of the mass of the epoxy resin in the bottom layer; and the mass of the modified SiO2 accounts for 30%-70% of the mass of the epoxy resin in the surface layer.

2. The superhydrophobic composite coating according to claim 1, wherein, The siloxane is dodecyltrimethoxysilane.

3. The superhydrophobic composite coating of claim 1, wherein, The thickness of the super-hydrophobic composite coating is 90-110 μm.

4. A method for producing the superhydrophobic composite coating according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: After MoS2, a Ce source and a buffer solution are mixed, dopamine hydrochloride is added, a self-polymerization reaction occurs, CeO2 is uniformly loaded on the surface of the two-dimensional layered structure of MoS2, and Ce-MoS2 fillers are obtained; The Ce-MoS2 fillers, a resin, a curing agent and a first solvent are uniformly mixed and coated on a substrate, and after curing, a bottom layer is obtained; The modified SiO2, the resin, the curing agent and a second solvent are uniformly mixed and coated on the bottom layer, and after curing, a surface layer coating is formed to obtain a super-hydrophobic composite coating.

5. The method of claim 4, wherein the method further comprises: The specific preparation method of the modified SiO2 is as follows: The SiO2 is dispersed in an ammonia solution, siloxane is added, stirring reaction is performed, and centrifugation is performed to obtain the modified SiO2; The dosage ratio of SiO2 to siloxane is 1 g:2 mL.

6. The method of claim 4, wherein the method further comprises: The mass ratio of MoS2 to the Ce source is 5:8; and the mass ratio of MoS2 to dopamine hydrochloride is 1:

1.

7. The method of claim 4, wherein the method further comprises: The temperature of the self-polymerization reaction is 40-50℃.

8. The method of claim 4, wherein the method further comprises: The first solvent is dimethylbenzene and n-butanol, and the mass ratio of dimethylbenzene to n-butanol is 7:3; The second solvent is ethyl acetate.

9. The method of claim 4, wherein the method further comprises: The resin is an epoxy resin.

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