Cu-MOFs (at) CuS (at) SA super-hydrophobic composite coating as well as preparation method and application thereof

Abstract

The invention discloses a Cu-MOFs (at) CuS (at) SA super-hydrophobic composite coating and a preparation method and application thereof.The preparation method comprises the steps that Cu (NO3) 2.3 H2O, nicotinic acid, PVP, L-cysteine and a mixed solvent are evenly mixed to obtain a mixed solution, the pretreated magnesium alloy surface is immersed in the mixed solution for a hydrothermal reaction, cooling, flushing and drying are conducted, a Cu-MOFs (at) CuS micro / nano rough layer is obtained, and the Cu-MOFs (at) CuS SA super-hydrophobic composite coating is obtained. And immersing the Cu-MOFs (at) CuS micro / nano rough layer into a stearic acid solution for modification treatment, taking out the Cu-MOFs (at) CuS micro / nano rough layer, drying, and repeating for multiple times to obtain the Cu-MOFs (at) CuS (at) SA super-hydrophobic composite coating. The one-step hydrothermal-post-modification coating provided by the invention has four functions of super-hydrophobicity, long-acting corrosion resistance, self-cleaning and inhibition of microbial induced corrosion (MIC) at the same time, and can be applied to lightweight structural components such as insulator connecting caps and the like.

Description

Technical Field

[0001] This invention belongs to the field of superhydrophobic coating technology, specifically relating to a Cu-MOFs@CuS@SA superhydrophobic composite coating, its preparation method, and its application. Background Technology

[0002] Ultra-high voltage (UHV) power transmission systems place dual demands on insulator auxiliary structures: lightweight design and long service life. AZ31B magnesium alloy has a low density (1.7 g / cm³). -3 It has high specific strength, but its standard electrode potential is only -2.37 V, making it susceptible to damage in high humidity, high salt spray, and environments containing SO2 and NO. x In industrial environments, a loose oxide film forms, inducing pitting corrosion and stress corrosion cracking. More seriously, the high humidity of tidal flats or heavy industrial areas promotes rapid microbial colonization, and their metabolic products react with Cl... - Synergistic effects lead to the destruction of biofilm-corrosion coupling, resulting in premature failure of critical components.

[0003] Superhydrophobic surfaces (contact angle >150°, roll-off angle <10°) can significantly reduce the retention of corrosive media. However, single organic or inorganic coatings are prone to cracking and peeling under ultra-high voltage conditions where wind, sand, corona discharge, and ultraviolet radiation coexist. Therefore, coatings must simultaneously possess high hardness, toughness, and environmental stability, posing a severe challenge to traditional designs.

[0004] Metal-organic frameworks (MOFs) have attracted significant attention in corrosion resistance, antibacterial applications, and metal protection due to their ultra-high specific surface area, tunable pore size, and abundant active sites. Specifically, their tunable structure and high porosity can significantly extend the diffusion path of corrosive media, thereby enhancing barrier properties. Simultaneously, the increased surface roughness further improves abrasion resistance. Furthermore, the ease of functionalization of MOFs allows them to be modified with low surface energy materials, providing a new approach for constructing superhydrophobic surfaces. However, while existing Cu-MOFs possess both catalytic activity and antibacterial potential, they are limited by insufficient water stability.

[0005] Therefore, there is an urgent need to develop a coating that combines high hardness, toughness, and environmental stability. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of the invention, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing Cu-MOFs@CuS@SA superhydrophobic composite coatings.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: After cutting, flattening, cleaning, and drying the magnesium alloy in sequence, chemical polishing is performed to obtain the pretreated magnesium alloy surface. Cu(NO3)2·3H2O, nicotinic acid, PVP, L-cysteine, and a mixed solvent are mixed evenly to obtain a mixed solution. The pretreated magnesium alloy surface is immersed in the mixed solution for hydrothermal reaction, followed by cooling, rinsing, and drying to obtain a Cu-MOFs@CuS micro / nano roughened layer. The mass ratio of Cu(NO3)2·3H2O, nicotinic acid, PVP, and L-cysteine ​​is 8:4:1:2~3. The concentration of Cu(NO3)2·3H2O in the mixed solution is 0.02~0.15 mol / L. The mixed solvent consists of deionized water and anhydrous ethanol. The Cu-MOFs@CuS micro / nano roughened layer was immersed in stearic acid solution for modification, then removed and dried. This process was repeated multiple times to obtain the Cu-MOFs@CuS@SA superhydrophobic composite coating.

[0010] In a preferred embodiment of the preparation method described in this invention, the pretreated magnesium alloy surface is immersed in a mixed solution for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 100~180℃ and the time is 9~11 h.

[0011] As a preferred embodiment of the preparation method described in this invention, the Cu-MOFs@CuS micro / nano roughened layer is immersed in a stearic acid solution for modification treatment, wherein the concentration of the stearic acid solution is 2~20 g / L.

[0012] In a preferred embodiment of the preparation method described in this invention, the modification treatment time is 1~30 min.

[0013] In a preferred embodiment of the preparation method described in this invention, the mixed solvent is composed of deionized water and anhydrous ethanol, wherein the volume ratio of deionized water to anhydrous ethanol is 1:1~6.

[0014] In a preferred embodiment of the preparation method described in this invention, the chemical polishing time is 40-60 min.

[0015] In a preferred embodiment of the preparation method described in this invention, the chemical polishing solution is a NaOH solution.

[0016] In a preferred embodiment of the preparation method described in this invention, the concentration of the NaOH solution is 1~6 mol·L⁻¹. -1 .

[0017] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing Cu-MOFs@CuS@SA superhydrophobic composite coatings.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of Cu-MOFs@CuS@SA superhydrophobic composite coating in lightweight structural components.

[0019] As a preferred embodiment of the application described in this invention, the lightweight structural components include, but are not limited to, insulator connectors, brackets, fasteners, and damping washers.

[0020] Beneficial effects of this invention: (1) This invention embeds CuS nanoparticles in situ into the MOF framework to form an organic-inorganic hierarchical channel. On the one hand, the high specific surface area of ​​MOFs can support low surface energy materials and construct a micro-nano rough structure to capture an air layer, effectively inhibiting the penetration of corrosive ions; on the other hand, CuS nanocrystals, as rigid pillars, can not only prevent crack propagation and improve mechanical toughness, but also release Cu through controlled release. 2+ Disrupting the bacterial cell membrane potential achieves a dual effect of structural reinforcement and functional synergy.

[0021] (2) The one-step hydrothermal-post-modification coating preparation method provided by the present invention is simple and scalable. The prepared superhydrophobic coating has a water contact angle ≥163° and a roll-off angle ≤10°. After 200 sandpaper abrasions, the contact angle is still ≥150°. The corrosion current density in 3.5 wt% NaCl solution is ≥2 orders of magnitude lower than that of the bare alloy. At the same time, the antibacterial rate against Escherichia coli and Staphylococcus epidermidis is ≥96%, which significantly inhibits microbial-induced corrosion.

[0022] (3) The coating system is constructed in situ on the AZ31B magnesium alloy substrate and has four functions: superhydrophobicity, long-term corrosion resistance, self-cleaning and inhibition of microbial induced corrosion (MIC). It can be applied to lightweight structural components such as insulator connectors, brackets, fasteners, and damping pads, and can achieve maintenance-free operation throughout the entire life cycle in extreme environments such as humid and hot salt spray, heavy industrial atmosphere and tidal flat biological pollution. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0024] Figure 1 The SEM morphology and contact angle of the superhydrophobic composite coatings prepared in Example 1 and Comparative Examples 1-3 of this invention are shown.

[0025] Figure 2 The coating durability curves for the coatings prepared in Example 1 and Comparative Example 3 of this invention were obtained by testing with sandpaper abrasion (a), tape peeling (b), and water jet impact (c).

[0026] Figure 3 These are comparison diagrams showing the self-adhesion of the coating surfaces in Example 1 and Comparative Examples 2-3 of the present invention.

[0027] Figure 4 The images show a comparison of the self-cleaning properties of the coating surfaces in Example 1 and Comparative Examples 2-3 of this invention.

[0028] Figure 5 This is a comparison chart of the corrosion current density of the coatings in Examples 1-2 and Comparative Examples 1-3 and 5-9 of the present invention.

[0029] Figure 6 The number of colonies in the culture medium after co-culturing the coatings of Examples 1-2 and Comparative Examples 1-3 and 5-9 of the present invention with Escherichia coli and Staphylococcus epidermidis for 24 hours.

[0030] Figure 7 The images show the SEM images of Escherichia coli and Staphylococcus epidermidis adhering to the coating surfaces of Examples 1-2 and Comparative Examples 1-3 and 5-9 after co-culturing for 24 hours. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0034] Example 1 This embodiment provides a method for preparing a Cu-MOFs@CuS@SA superhydrophobic composite coating, specifically as follows: (1) Pretreatment of AZ31B magnesium alloy: AZ31B magnesium alloy was cut into 35 mm × 35 mm × 1 mm samples, mechanically flattened, ultrasonically cleaned in anhydrous ethanol for 20 min to remove surface grease and impurity particles, rinsed with deionized water, and dried at 50 ℃ for 30 min. The dried samples were immediately immersed in 3 mol·L -1 Chemical polishing was performed in NaOH solution at room temperature for 40 min to remove the natural oxide film and obtain a smooth surface, thereby enhancing the chemical reactivity of the magnesium alloy. Then, it was rinsed with deionized water and dried for later use. (2) Hydrothermal in-situ growth of Cu-MOFs@CuS composite coating: Cu(NO3)2·3H2O, nicotinic acid (NA), and PVP were dissolved in a mixed solvent of deionized water and anhydrous ethanol. The solution was sonicated for 10 min to obtain a clear solution. L-cysteine ​​was added and stirred evenly to obtain a mixed solution. The mass ratio of Cu(NO3)2·3H2O: nicotinic acid: PVP: L-cysteine ​​was 8:4:1:3. The volume ratio of deionized water to anhydrous ethanol in the mixed solvent was 1:3.57. The concentration of Cu(NO3)2·3H2O in the mixed solution was 0.05 mol / L. The pretreated AZ31B magnesium alloy surface was immersed in a mixed solution and hydrothermally reacted at 160℃ for 10 h. After cooling to room temperature, it was rinsed with deionized water and dried to obtain a Cu-MOFs@CuS micro / nano roughened layer on the magnesium alloy surface.

[0035] (3) Hydrophobic modification: Stearic acid (SA) was dissolved in anhydrous ethanol to obtain a 10 g / L modification solution. The coating obtained in step (2) was immersed in the modification solution for 5 min, removed and dried. This process was repeated 3 times to obtain Cu-MOFs@CuS 0.3 @SA superhydrophobic composite coating.

[0036] Example 2 This embodiment provides a method for preparing a Cu-MOFs@CuS@SA superhydrophobic composite coating, specifically as follows: (1) Pretreatment of AZ31B magnesium alloy: AZ31B magnesium alloy was cut into 35 mm × 35 mm × 1 mm samples, mechanically flattened, ultrasonically cleaned in anhydrous ethanol for 20 min to remove surface grease and impurity particles, rinsed with deionized water, and dried at 50℃ for 30 min. The dried samples were immediately immersed in 1 mol·L⁻¹ ethanol. -1 Chemical polishing was performed in NaOH solution at room temperature for 60 min to remove the natural oxide film and obtain a smooth surface, thereby enhancing the chemical reactivity of the magnesium alloy. Then, it was rinsed with deionized water and dried for later use. (2) Hydrothermal in-situ growth of Cu-MOFs@CuS composite coating: Cu(NO3)2·3H2O, nicotinic acid (NA), and PVP were dissolved in a mixed solvent of deionized water and anhydrous ethanol. The solution was sonicated for 10 min to obtain a clear solution. L-cysteine ​​was added and stirred evenly to obtain a mixed solution. The mass ratio of Cu(NO3)2·3H2O: nicotinic acid: PVP: L-cysteine ​​was 8:4:1:2. The volume ratio of deionized water to anhydrous ethanol in the mixed solvent was 1:6. The concentration of Cu(NO3)2·3H2O in the mixed solution was 0.02 mol / L. The pretreated AZ31B magnesium alloy surface was immersed in a mixed solution and hydrothermally reacted at 100℃ for 9 h. After cooling to room temperature, it was rinsed with deionized water and dried to obtain a Cu-MOFs@CuS micro / nano roughened layer on the magnesium alloy surface.

[0037] (3) Hydrophobic modification: Stearic acid (SA) was dissolved in anhydrous ethanol to obtain a 2 g / L modification solution. The coating obtained in step (2) was immersed in the modification solution for 30 min, removed and dried. This process was repeated 3 times to obtain Cu-MOFs@CuS 0.2 @SA superhydrophobic composite coating.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that the mass ratio of Cu(NO3)2·3H2O:nicotinic acid:PVP:L-cysteine ​​in step (2) is adjusted to 8:4:1:1 and 8:4:1:4, respectively. The rest of the preparation method is the same as in Example 1, and the Cu-MOFs@CuS of this comparative example are obtained. 0.1 SA, Cu-MOFs@CuS 0.4 SA superhydrophobic composite coating.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that step (2) of preparing the Cu-MOFs@CuS composite coating was not performed. The rest of the preparation methods are the same as in Example 1, and the AZ31B@SA coating of this comparative example is obtained.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that L-cysteine ​​was not added in step (2), while the rest of the preparation methods were the same as in Example 1, resulting in the Cu-MOFs@SA coating of this comparative example.

[0041] Figure 1 The SEM morphology and corresponding contact angles of the coatings prepared in Examples 1 and Comparative Examples 1-3 are shown. Among them, (a) is the AZ31B@SA coating obtained in Comparative Example 3, (b) is the Cu-MOFs@SA coating obtained in Comparative Example 2, (c) is the superhydrophobic coating obtained in Comparative Example 1 when the mass ratio of Cu(NO3)2·3H2O:nicotinic acid:PVP:L-cysteine ​​is 8:4:1:1, (d) is the superhydrophobic coating obtained in Comparative Example 1 when the mass ratio of Cu(NO3)2·3H2O:nicotinic acid:PVP:L-cysteine ​​is 8:4:1:2, and (e) is the superhydrophobic coating obtained in Example 1.

[0042] The contact angles of the coatings in Test Example 1 and Comparative Examples 1-3 are shown in Table 1.

[0043] Table 1. Effects of L-cysteine ​​addition and copper source addition on the hydrophobic properties of the coating.

[0044] According to Table 1 and Figure 1 As can be seen, the water contact angle (WCA) after SA modification is only 78°. Hydrothermal growth of Cu-MOFs, with its interlocking plate-particle structure, initially increases roughness, raising the WCA to 136°. With an L-cysteine ​​ratio of 8:4:1:1, CuS is formed, resulting in a micro / nanofiber network and submicron pores on the surface, achieving a WCA of 152°. Increasing the L-cysteine ​​ratio to 8:4:1:2 leads to the formation of a needle-plate three-dimensional framework, further improving roughness, with a WCA of 158°. Further increasing the L-cysteine ​​ratio to 8:4:1:3 enlarges the microplates, transforms the needles into fibers, resulting in uniform weaving and abundant porosity, raising the WCA to 162°, laying the foundation for superhydrophobicity. However, when the L-cysteine ​​ratio continues to increase to 8:4:1:4, the contact angle decreases to 155°. It can be seen that only L-cysteine ​​ratios within the range of this invention can achieve the preparation of superhydrophobic coatings.

[0045] Figure 2 Cu-MOFs@CuS prepared in Example 1 0.3 The durability of the Cu-MOFs@SA prepared in @SA and Comparative Example 3 was tested by abrasion with sandpaper (a), tape peeling (b), and water jet impact test (c).

[0046] according to Figure 2(a) After 120 sandpaper abrasions, the WCA of Cu-MOFs@SA dropped sharply, losing its superhydrophobicity, while that of Cu-MOFs@CuS 0.3 @SA maintains a value >150°, CuS reinforces the framework, and the micro / nano structure remains intact. Figure 3 (b) After 200 peels of the tape, the WCA of the former dropped to 110°, while that of the latter remained >155°, and the water droplets remained spherical. Figure 2 (c) After 15 min of water jet impact, the WCA of the former decreased to 116°, while that of the latter remained at 154°. Multiple tests show that the appropriate introduction of CuS significantly improves the mechanical stability of the coating. Combined with the low surface energy of stearic acid, it can effectively resist abrasion, tearing and impact forces and maintain superhydrophobic properties for a long time.

[0047] The surface adhesion and self-cleaning properties of the coatings in Example 1 and Comparative Examples 2-3 were tested, and the results are as follows: Figures 3-4 As shown.

[0048] Figure 3 The results are as follows: (a) shows the surface adhesion test results, where (a) represents AZ31B@SA, Cu-MOFs@SA, and Cu-MOFs@CuS. 0.3 The morphology of various droplets on the @SA coating clearly shows that, compared with the AZ31B@SA and Cu-MOFs@SA surfaces, Cu-MOFs@CuS 0.3 @SA surface droplets are spherical; (b) shows droplets on AZ31B@SA and Cu-MOFs@CuS 0.3 Wetting behavior of @SA surface, Cu-MOFs@CuS 0.3 @SA surface showed no spread after 2 minutes and rolled off the 45° slope instantly, while AZ31B@SA surface did not slide off after 2 minutes and eventually left a mark on the surface; (c) water flow impact on Cu-MOFs@CuS 0.3 The dynamics of the @SA coating surface show that no residue remains due to water droplet bounce; (d) shows Cu-MOFs@CuS 0.3 The @SA coating exhibits a silver mirror effect underwater, demonstrating the presence of the Cassie-Baxter air cushion effect; (e) shows water droplets on Cu-MOFs@CuS 0.3 The sliding process at any position on the @SA surface; (f) shows the water droplet approaching, contacting, and detaching from Cu-MOFs@CuS. 0.3 A series of photos of the @SA coated surface, showing how the needle tip water droplets detach freely due to the ultra-low adhesion of the droplets.

[0049] Figure 4The results of the self-cleaning test are shown in (a) and (b) for the self-cleaning process of the AZ31B@SA coating surface against lime (left) and soot (right) contaminants. It can be seen that only a very small amount of dust is swept away by the rolling water droplets. 0.3 The self-cleaning process of @SA coating surface against lime (left) and soot (right) contaminants, (c) for Cu-MOFs@CuS 0.3 The @SA coating surface exhibits a self-cleaning process against various liquids such as salt water, acid, juice, and cola. Almost all dust on the surface of this composite coating is swept away by the rolling water droplets, leaving a clean trail. In addition, it maintains a contact angle of >150° with salt water, acid, juice, and cola, causing the droplets to bounce away contaminants.

[0050] Comparative Example 5 The difference between this comparative example and Example 1 is that the hydrophobic modification in step (4) is not performed; the rest of the preparation methods are the same as in Example 1, resulting in Cu-MOFs@CuS in this comparative example. 0.3 coating.

[0051] Comparative Example 6 The difference between this comparative example and Example 2 is that the hydrophobic modification in step (4) is not performed. The rest of the preparation methods are the same as in Example 2, resulting in Cu-MOFs@CuS in this comparative example. 0.2 coating.

[0052] Comparative Example 7 The difference between this comparative example and Comparative Example 1 is that the hydrophobic modification in step (4) is not performed. The rest of the preparation methods are the same as those in Comparative Example 1, resulting in Cu-MOFs@CuS in this comparative example. 0.1 Cu-MOFs@CuS 0.4 coating.

[0053] Comparative Example 8 The difference between this comparative example and comparative example 2 is that the hydrophobic modification in step (4) is not performed, and the rest of the preparation methods are the same as those in comparative example 2, so as to obtain the AZ31B substrate of this comparative example.

[0054] Comparative Example 9 The difference between this comparative example and comparative example 3 is that the hydrophobic modification in step (4) is not performed, and the rest of the preparation methods are the same as those in comparative example 3, so as to obtain the Cu-MOFs coating of this comparative example.

[0055] Potentiodynamic polarization tests were performed on the coatings of Examples 1-2 and Comparative Examples 1-3 and 5-9, and the results are as follows: Figure 5 As shown.

[0056] Figure 5In the figures, (a) represents the corrosion current density of AZ31B magnesium alloy before and after SA modification; (b) represents the corrosion current density of magnesium alloy after SA modification following Cu-MOFs coating; (c) represents the corrosion current density of Cu-MOFs after SA modification following CuS (8:4:1:1) incorporation; (d) represents the corrosion current density of Cu-MOFs after SA modification following CuS (8:4:1:2) incorporation; and (e) represents the corrosion current density of Cu-MOFs after SA modification following CuS (8:4:1:3) incorporation.

[0057] Comparing (a), (b), and (c), the corrosion current density of AZ31B significantly decreased after being covered with Cu-MOFs. Further doping with CuS resulted in a decrease in corrosion current density with increasing Cu-MOF@CuS dosage. 0.3 The composite coating exhibits the lowest corrosion current density and the best corrosion resistance. (Comparisons are provided.) Figure 5 The two curves in each figure show that stearic acid outer layer modification further reduces corrosion current density, particularly in Cu-MOFs@CuS. 0.3 The @SA superhydrophobic coating reduces corrosion by two orders of magnitude compared to the bare substrate. This is because its micro-nano rough structure traps an air film, drastically reducing the solid-liquid contact area and hindering the penetration of corrosive ions; the multi-layered dense framework extends the diffusion path, providing long-lasting protection for AZ31B.

[0058] After co-culturing the coatings of Examples 1-2 and Comparative Examples 1-3 and 5-9 with Escherichia coli and Staphylococcus epidermidis for 24 hours, the coatings were removed, and the number of colonies in the culture medium was tested. The results are as follows: Figure 6 As shown. (a) represents the number of bacteria after 24 hours of pure bacterial culture, and the number of bacteria cultured with AZ31B, Cu-MOFs, and Cu-MOFs@CuS, respectively. 0.1 Cu-MOFs@CuS 0.2 and Cu-MOFs@CuS 0.3 The number of bacteria in the culture medium after co-culturing for 24 hours. (b) AZ31B@SA, Cu-MOFs@SA, Cu-MOFs@CuS 0.1 @SA、Cu-MOFs@CuS 0.2 @SA、Cu-MOFs@CuS 0.3 The number of bacteria in the culture medium after co-culturing with SA for 24 hours.

[0059] contrast Figure 6In (a) and (b), AZ31B and AZ31B@SA showed dense colonies with an antibacterial rate of <10%. The Cu-MOFs coating drastically reduced the number of E. coli and S. epidermidis, achieving an inhibition rate of 98%. SA modification did not reduce the bactericidal activity. After the introduction of CuS, the Cu-MOFs@CuS and Cu-MOFs@CuS@SA coatings both achieved an inhibition rate of 100%. This is due to the Cu... 2+ This is caused by damage to the membrane integrity.

[0060] SEM images of Escherichia coli and Staphylococcus epidermidis adhesion on the surfaces of each coating were obtained after co-culturing the coatings of Examples 1-2 and Comparative Examples 1-3 and 5-9 for 24 hours. The results are as follows: Figure 7 As shown in the figure, (a) represents the calculated antibacterial rate of bacterial colonies on each coating, and (b) to (f) are SEM images of the adhesion morphology of Staphylococcus epidermidis on the surface of each coating. The SEM images clearly show that the bacteria on the AZ31B@SA surface are plump and intact, while the adhesion on the Cu-MOFs surface is sharply reduced and the bacteria collapse. Only the Cu-MOFs@CuS@SA surface is almost sterile, with remaining bacteria shrinking, cytoplasmic leakage, and blurred membrane structure. This indicates that only when micro-nano roughness and superhydrophobicity work together can bacterial adhesion be reduced and cells physically torn apart, thus blocking biofilm formation and providing durable antibacterial and corrosion-resistant protection for magnesium alloys in the intertidal zone and the high-humidity, high-temperature, and acidic environments of heavy industry.

[0061] Comparative Example 6 The difference between this comparative example and Example 1 is that the hydrothermal time in step (2) is adjusted to 4h, 6h, and 8h respectively, while the rest of the preparation method is the same as in Example 1, to obtain Cu-MOFs@CuS in this comparative example. 0.3 @SA composite coating.

[0062] The morphology of the composite coating obtained in Comparative Example 5 is as follows: Figure 1 As shown in (f) to (h). Where (f) is 8h, (g) is 6h, and (h) is 4h. (Comparison) Figure 1 As can be seen from (e) and (f) to (h), 10h has a sea urchin-like shape, dense fibers and spines, the greatest roughness, and therefore the largest contact angle; 8h has a similar morphology but the spines are slightly blunt; 6h has blunted spines and decreased roughness; 4h has no spines, dense particles, and a flat surface.

[0063] Comparative Example 6: Cu-MOFs@CuS prepared with different hydrothermal times 0.3 The water contact angle of the @SA composite coating is shown in Table 2.

[0064] Table 2. Effect of different hydrothermal times on the hydrophobicity of the composite coating.

[0065] Comprehensive morphology ( Figure 1 When the ratio of L-cysteine ​​(f) to WCA (Table 2) is 8:4:1:3, the Cu-MOFs@CuS coating exhibits excellent micro / nano structure and superior superhydrophobic properties only under hydrothermal conditions for 10 h. 0.3 @SA.

[0066] Example 3 This embodiment provides a method for preparing a Cu-MOFs@CuS@SA superhydrophobic composite coating, specifically as follows: (1) Pretreatment of AZ31B magnesium alloy: AZ31B magnesium alloy was cut into 35 mm × 35 mm × 1 mm samples, mechanically flattened, ultrasonically cleaned in anhydrous ethanol for 20 min to remove surface grease and impurity particles, rinsed with deionized water, and dried at 50℃ for 30 min. The dried samples were immediately immersed in 6 mol·L⁻¹ water. -1 Chemical polishing was performed in NaOH solution at room temperature for 40 min to remove the natural oxide film and obtain a smooth surface, thereby enhancing the chemical reactivity of the magnesium alloy. Then, it was rinsed with deionized water and dried for later use. (2) Hydrothermal in-situ growth of Cu-MOFs@CuS composite coating: Cu(NO3)2·3H2O, nicotinic acid (NA), and PVP were dissolved in a mixed solvent of deionized water and anhydrous ethanol. The solution was sonicated for 10 min to obtain a clear solution. L-cysteine ​​was added and stirred evenly to obtain a mixed solution. The mass ratio of Cu(NO3)2·3H2O: nicotinic acid: PVP: L-cysteine ​​was 8:4:1:3. The volume ratio of deionized water to anhydrous ethanol in the mixed solvent was 1:1. The concentration of Cu(NO3)2·3H2O in the mixed solution was 0.15 mol / L. The pretreated AZ31B magnesium alloy surface was immersed in a mixed solution and hydrothermally reacted at 180℃ for 11 h. After cooling to room temperature, it was rinsed with deionized water and dried to obtain a Cu-MOFs@CuS micro / nano roughened layer on the magnesium alloy surface.

[0067] (4) Hydrophobic modification: Stearic acid (SA) was dissolved in anhydrous ethanol to obtain a 20 g / L modification solution. The coating obtained in step (2) was immersed in the modification solution for 1 min, removed and dried. This process was repeated 3 times to obtain Cu-MOFs@CuS 0.2 @SA superhydrophobic composite coating.

[0068] The superhydrophobic coating obtained in Example 3 has similar performance to that in Examples 1 and 2, but Example 1 has the best effect.

[0069] In summary, this invention constructs a Cu-MOFs@CuS micro-nano rough framework in situ on the surface of AZ31B magnesium alloy using a one-step hydrothermal method, and then modifies it with stearic acid for low surface energy, in order to obtain a multifunctional composite protective layer Cu-MOFs@CuS@SA that combines superhydrophobicity, long-lasting corrosion resistance and high-efficiency antibacterial properties.

[0070] The coating exhibits a water contact angle ≥163° and a roll-off angle ≤10°. After 200 sandpaper abrasions, the contact angle remains ≥150°. In a 3.5 wt% NaCl solution, the corrosion current density is reduced by ≥2 orders of magnitude compared to the bare alloy. Simultaneously, it demonstrates an inhibition rate of ≥96% against Escherichia coli and Staphylococcus epidermidis, significantly suppressing microbial-induced corrosion. This invention features a simple process and excellent performance, making it suitable for the long-term reliable service of lightweight components such as UHV insulator connectors in extreme environments.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a Cu-MOFs@CuS@SA superhydrophobic composite coating, characterized in that: include, After cutting, flattening, cleaning, and drying the magnesium alloy in sequence, chemical polishing is performed to obtain the pretreated magnesium alloy surface. Cu(NO3)2·3H2O, nicotinic acid, PVP, L-cysteine, and a mixed solvent are mixed evenly to obtain a mixed solution. The pretreated magnesium alloy surface is immersed in the mixed solution for hydrothermal reaction, followed by cooling, rinsing, and drying to obtain a Cu-MOFs@CuS micro / nano roughened layer. The mass ratio of Cu(NO3)2·3H2O, nicotinic acid, PVP, and L-cysteine ​​is 8:4:1:2~3. The concentration of Cu(NO3)2·3H2O in the mixed solution is 0.02~0.15 mol / L. The mixed solvent consists of deionized water and anhydrous ethanol. The Cu-MOFs@CuS micro / nano roughened layer was immersed in stearic acid solution for modification, then removed and dried. This process was repeated multiple times to obtain the Cu-MOFs@CuS@SA superhydrophobic composite coating.

2. The preparation method according to claim 1, characterized in that: The pretreated magnesium alloy surface is immersed in a mixed solution for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 100~180℃ and the time is 9~11 h.

3. The preparation method according to claim 1, characterized in that: The process involves immersing the Cu-MOFs@CuS micro / nano roughened layer in a stearic acid solution for modification, wherein the concentration of the stearic acid solution is 2~20 g / L.

4. The preparation method according to claim 3, characterized in that: The modification treatment takes 1 to 30 minutes.

5. The preparation method according to claim 1, characterized in that: The mixed solvent is composed of deionized water and anhydrous ethanol, wherein the volume ratio of deionized water to anhydrous ethanol is 1:1 to 6.

6. The preparation method according to claim 1, characterized in that: The chemical polishing time is 40-60 minutes.

7. The preparation method according to claim 1, characterized in that: The chemical polishing solution is a NaOH solution.

8. The preparation method according to claim 7, characterized in that: The concentration of the NaOH solution is 1~6 mol·L⁻¹ -1 .

9. The Cu-MOFs@CuS@SA superhydrophobic composite coating prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the Cu-MOFs@CuS@SA superhydrophobic composite coating as described in claim 9 in lightweight structural components, characterized in that: The lightweight structural components include, but are not limited to, insulator connectors, brackets, fasteners, and damping washers.

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