A coating with high adhesion, antifouling and drag reduction for titanium alloy substrates, its preparation method and application.

Abstract

This application relates to the field of metal material surface treatment technology, and in particular to a coating for bonding strength, antifouling, and drag reduction in titanium alloy pipes, its preparation method, and its application. The preparation method includes the following steps: micro-arc oxidation treatment of the titanium alloy to form a ceramic film on the surface; hydrothermal reaction of the micro-arc oxidized titanium alloy to introduce nanoscale porous thorn microstructures and hydroxyl groups onto the ceramic film surface; coating a prepolymer onto the hydrothermally treated titanium alloy and reacting it under ultraviolet light to obtain a first network gel; immersing the first network gel in a β-glycerophosphate sodium salt solution to form an ion-covalent double network p(SBMA-co-AAc) / CS-β-GP DN hydrogel. The coating prepared by the method provided in this application exhibits improved stability and durability, long-term stable antifouling performance, strong bonding with the titanium alloy substrate, and excellent antifouling and drag reduction effects when applied to titanium alloy substrates.

Description

Technical Field

[0001] This application relates to the field of metal material surface treatment technology, and in particular to a coating with high adhesion, anti-fouling and drag reduction for titanium alloy substrates, its preparation method and application. Background Technology

[0002] Titanium alloys, as a manufacturing material for marine structures, have been widely used in marine equipment seawater pipeline engineering due to their excellent properties such as high specific strength, strong corrosion resistance, and light weight.

[0003] However, in the long-term marine environment, the excellent biocompatibility of titanium alloys makes their surfaces susceptible to severe biofouling. This fouling not only increases ocean current resistance and reduces heat transfer efficiency, but can also lead to a series of consequences such as power plant failure and corrosion beneath the fouling layer. To address this, researchers have proposed using highly adhesive zwitterionic hydrogels as protective coatings for titanium alloy structures. These zwitterionic hydrogels not only optimize the microstructure of the material surface but also achieve intelligent control of the material's surface wettability through their unique chemical composition design.

[0004] Traditional superhydrophobic surfaces construct an air layer through surface microstructure and low surface energy modification, forming a solid-gas-liquid three-phase interface. This air layer prevents direct contact between marine organisms and the solid surface, while also reducing frictional resistance between the fluid and the surface, achieving antifouling and drag reduction. Hydrogel surfaces, through their internal microstructure and chemical composition, utilize their excellent water absorption and retention capabilities to form a stable hydration layer on the surface. This hydration layer replaces the solid surface, forming a liquid-liquid interface, significantly reducing the contact area and adhesion between marine organisms and the structure's surface. Simultaneously, the liquid-liquid interface further reduces the frictional resistance of seawater on the structure, achieving antifouling and drag reduction effects.

[0005] Superhydrophobic surfaces transform the solid-liquid interface into a free shear surface for gas-liquid contact, forming an air cushion on the solid surface to generate velocity slip and reduce viscous drag. However, their three-phase surface energy barrier is easily broken at pipe flow rates, and the wetted state transitions from the Cassie-Baxter state to the Wenzel state due to the rupture or depletion of the trapped gas, resulting in the loss of drag-reduction properties, as is the case with superlubricated surfaces. Therefore, thermodynamic instability hinders the long-term application of superhydrophobic (superlubricated) surfaces. Furthermore, hydrophilic coatings gradually weaken their hydration capacity at high flow rates, thus impairing their antifouling and drag-reduction properties. Summary of the Invention

[0006] To address the shortcomings of the prior art mentioned in the background section, this application provides a method for preparing a coating with high adhesion, anti-fouling properties, and drag reduction for titanium alloy substrates. The technical solution is as follows:

[0007] The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates provided in this application includes the following steps:

[0008] Micro-arc oxidation: Micro-arc oxidation is performed on titanium alloys to form a ceramic film on the surface of the titanium alloys;

[0009] Hydrothermal treatment: The titanium alloy after micro-arc oxidation is subjected to a hydrothermal reaction to introduce nanoscale porous thorn microstructures and hydroxyl groups on the surface of the ceramic film;

[0010] Hydrogel coating: The prepolymer is coated onto the hydrothermally treated titanium alloy, and the reaction is carried out under ultraviolet light to obtain the first network gel, which is the final product;

[0011] The prepolymer liquid is a slightly yellow, viscous liquid formed by reacting a mixture at room temperature under a protective atmosphere; the mixture is a mixed solution formed by mixing chitosan, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, α-ketoglutaric acid, and acrylic acid in water.

[0012] In some embodiments, after the first network gel is formed, the first network gel is post-treated; the post-treatment process is as follows: the first network gel is immersed in a β-glycerophosphate sodium salt solution to form an ion-covalent dual network p(SBMA-co-AAc) / CS-β-GP DN hydrogel.

[0013] In some embodiments, the prepolymer is coated onto a hydrothermally treated titanium alloy and reacted under ultraviolet light for 7-12 hours to obtain a first network gel; the first network gel is then immersed in a β-glycerophosphate sodium salt solution for 0.5-8 hours to form an ion-covalent double network p(SBMA-co-AAc) / CS-β-GP DN hydrogel.

[0014] The preparation process of the prepolymer solution is as follows: chitosan and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide are dissolved in water to form a mixture; then α-ketoglutaric acid and acrylic acid are added to the mixture, and the mixture is reacted at room temperature under a nitrogen atmosphere for 10-20 minutes to obtain a slightly yellow viscous liquid. Finally, the air bubbles in the slightly yellow viscous liquid are eliminated to obtain the prepolymer solution; in the mixture, the mass ratio of chitosan to water is 1-10:100. The molar concentration of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 1 mol / L to 5 mol / L; the molar ratio of α-ketoglutaric acid to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 0.1 to 2:100; the molar ratio of acrylic acid to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 1 to 10:100.

[0015] In some embodiments, the micro-arc oxidation process is as follows: an electrolyte is placed in an electrolytic cell, and then a titanium alloy is placed in the electrolyte as the anode, with a metal sheet in the electrolytic cell serving as the cathode; a bipolar pulse micro-arc oxidation power supply is activated to perform micro-arc oxidation; and then the titanium alloy is cleaned; wherein, the electrolyte temperature is below 20°C throughout the micro-arc oxidation process, and a constant current mode is used throughout, with a current density of 0.5–2 mA / cm². 2 The frequency is 300–2000 Hz, the duty cycle is 3–10%, the deposition time is 300–1200 s, and the termination voltage is 400–650 V.

[0016] In some embodiments, the electrolyte comprises silicate, glycerol, potassium fluoride, phosphate, sodium hydroxide, and water; wherein the concentrations of silicate, glycerol, potassium fluoride, phosphate, and sodium hydroxide in the electrolyte are 5–15 g / L, 3–9 g / L, 0–10 g / L, 0–5 g / L, and 5–15 g / L, respectively; and wherein the metal sheet is made of stainless steel.

[0017] In some embodiments, the hydrothermal reaction process is as follows: the titanium alloy after micro-arc oxidation treatment is immersed in an alkaline solution preheated to 20-60°C for 0.5-4 hours at 20-60°C; then the titanium alloy is removed and immersed in a dithiothreitol dilution solution, and the pH of the dithiothreitol dilution solution is adjusted to 6-6.5 with alkali, and stirred at room temperature for 10-60 minutes to introduce nanoscale microstructures and hydroxyl groups onto the surface of the ceramic film.

[0018] In some embodiments, during the hydrothermal reaction, the pH of the dithiothreitol dilution is adjusted with sodium hydroxide; the alkaline solution is a 1-8 wt% sodium hydroxide aqueous solution; the molar concentration of the dithiothreitol dilution is 0.01-0.05 mol / L; after the hydrothermal reaction is completed, the titanium alloy is removed and stored at low temperature for later use.

[0019] In some embodiments, the titanium alloy surface is polished and cleaned sequentially before the micro-arc oxidation treatment.

[0020] This application also provides a coating for high adhesion, antifouling and drag reduction on titanium alloy substrates, which is prepared by the method described above.

[0021] This application also provides the application of the coating described above for high adhesion, antifouling and drag reduction on titanium alloy substrates in the surfaces of ships, bridges, docks, offshore platforms, petroleum, chemical, transportation, aviation and various titanium metal structures.

[0022] Based on the above, compared with the prior art, the method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates provided in this application has the following beneficial effects:

[0023] The coating prepared by the method provided in this application has improved stability and durability, and has long-term stable antifouling performance. It has a strong bond with the titanium alloy substrate and has excellent antifouling and drag reduction effects when applied to the titanium alloy substrate.

[0024] Other features and beneficial effects of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other beneficial effects of this application may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] Figure 1 SEM images of titanium alloy surfaces under different processing techniques;

[0027] Figure 2 FTIR-ATR (Fourier Transform Infrared) spectra of titanium alloy surface coatings under different processing techniques;

[0028] Figure 3 Figures showing the contamination status of titanium alloy surfaces after a 45-day test on marine sidings under different treatment processes.

[0029] Figure 4 The graph shows the surface friction coefficient curves of titanium alloys under different processing techniques. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The technical features designed in the different implementations of this application described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] In the description of this application, it should be noted that all terms used in this application (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains, and should not be construed as limiting this application; it should be further understood that the terms used in this application should be understood to have the same meaning as those in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this application.

[0032] 1. This application provides the following embodiments and comparative examples:

[0033] Example 1: Preparation of MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample

[0034] Step 1, Polishing and Cleaning:

[0035] First, the surface of the titanium alloy TA24 was polished sequentially using 400#, 800#, 1200#, 2000# SiC sandpaper. Then, it was ultrasonicated for 15 minutes each in deionized water and anhydrous ethanol, and then dried for later use. This was recorded as the polished TA24 sample.

[0036] Step 2, Micro-arc oxidation (MAO):

[0037] The prepared electrolyte was poured into the electrolytic cell and agitated with air for 10 minutes to ensure complete dissolution. Then, the cleaned and polished TA24 was placed in the electrolyte as the anode, and a stainless steel sheet in the electrolytic cell served as the cathode. The bipolar pulsed micro-arc oxidation power supply was started to perform micro-arc oxidation treatment. An external water cooling circulation device was used to control the electrolyte temperature below 20℃ throughout the micro-arc oxidation process, and a constant current mode was used throughout the process. The power supply parameters were set as follows: current density 1.5 mA / cm². 2 The frequency was 800 Hz, the duty cycle was 6%, the deposition time was 600 s, and the termination voltage was 600 V. After the experiment, the water cooling circulation device and power switch were turned off, the sample was taken out, washed with anhydrous ethanol, dried, and placed in a petri dish for later use.

[0038] The sample treated with MAO is denoted as MAO-x sample or MAO-TA24(y) sample, where x represents the MAO termination voltage and y represents the deposition time.

[0039] The electrolyte consists of silicate (Na₂SiO₃·9H₂O), glycerol (C₃H₈O₃), potassium fluoride (KF), phosphate (Na₃PO₃·12H₂O), sodium hydroxide (NaOH), and water. All reagents are of analytical grade. The concentrations of silicate, glycerol, potassium fluoride, phosphate, and sodium hydroxide are 15 g / L, 6 g / L, 7 g / L, 2 g / L, and 7 g / L, respectively. Potassium fluoride is added to increase the conductivity of the solution.

[0040] Step 3, hydrothermal reaction:

[0041] (1) Preparation of MAO-TA24-hydrothermal treated sample

[0042] The titanium alloy after micro-arc oxidation treatment was immersed in an alkaline solution preheated to 40°C and immersed at 40°C for 4 hours to form a porous micro-nano structure on the coating surface. The titanium alloy was then removed and the resulting sample was named MAO-TA24-hydrothermal treatment sample.

[0043] The alkaline solution is a 4 wt% sodium hydroxide aqueous solution.

[0044] (2) Preparation of MAO-TA24-CuS complex sample

[0045] The titanium alloy was immersed in a dithiothreitol (DTT) diluent, and the pH of the dithiothreitol diluent was adjusted to 6.50 with sodium hydroxide. The mixture was stirred at room temperature for 30 minutes to introduce nanoscale microstructures and hydroxyl groups onto the surface of the ceramic film. The titanium alloy was then removed and stored at a low temperature of 4°C for later use. The resulting sample was designated as the MAO-TA24-CuS complex sample.

[0046] The dithiothreitol dilution has a molar concentration of 0.033 mol / L. The preparation process is as follows: 50 mL (0.1 mol / L) of dithiothreitol solution and 100 mL of ultrapure water are added to a beaker and mixed to obtain the dithiothreitol dilution.

[0047] Step 4, Hydrogel Coating:

[0048] (1) The preparation process of the prepolymer solution is as follows:

[0049] Chitosan and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) were dissolved in water to form a mixture; then α-ketoglutaric acid and acrylic acid (AAc) were added to the mixture and reacted at room temperature for 10 min under a nitrogen atmosphere to obtain a slightly yellow viscous liquid. Finally, the mixture was sonicated for 5 min to eliminate air bubbles in the slightly yellow viscous liquid to obtain a prepolymer solution.

[0050] In the mixture, the mass ratio of chitosan to water is 1:100 (i.e., 1g of chitosan is added to 100g of water), the molar concentration of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 3mol / L, the molar ratio of α-ketoglutaric acid to acrylic acid is 1:100, and the molar ratio of acrylic acid to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 5:100.

[0051] (2) Preparation of MAO-TA24-OH-p(AA-SBMA) / CS sample

[0052] The prepolymer solution was coated onto the hydrothermally treated titanium alloy, and the reaction was carried out under ultraviolet light for 8 hours to obtain the first network gel, thus obtaining the coating.

[0053] (3) Preparation of MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample

[0054] The first network gel was immersed in a β-glycerophosphate sodium salt solution for 4 hours to form an ion-covalent double network p(SBMA-co-AAc) / CS-β-GP DN hydrogel, which is the post-treated coating.

[0055] Comparative Example 1: TA24 sample after polishing

[0056] The sample obtained by only the treatment in step 1 of Example 1: polished TA24 sample.

[0057] Comparative Example 2: MAO-TA24 (10 minutes) sample

[0058] The sample obtained by processing step 1-2 of Example 1: MAO-TA24 (10 minutes) sample.

[0059] Comparative Example 3: MAO-TA24-hydrothermal treated sample

[0060] The sample obtained after processing in steps 1-3 (1) of Example 1: MAO-TA24-hydrothermal treated sample.

[0061] Comparative Example 4: MAO-TA24-CUS complex sample

[0062] The sample obtained after processing in steps 1-3 (2) of Example 1: MAO-TA24-CUS complex sample.

[0063] Comparative Example 5: MAO-TA24-OH-p(AA-SBMA) / CS sample

[0064] The sample obtained after processing in steps 1-4 (2) of Example 1: MAO-TA24-OH-p(AA-SBMA) / CS sample.

[0065] Comparative Example 6: MAO-TA24-Hydrothermal-treated-SHS sample

[0066] The sample obtained after processing in steps 1-3 (1) of Example 1 is then immersed in a silane solution for 4 hours and then baked at 100°C for 60 minutes to obtain a superhydrophobic surface.

[0067] The silane solution was prepared by mixing 0.1 ml of 1H,1H,2H,2H-perfluorooctyltrichlorosilane with 100 ml of ethanol solvent.

[0068] 2. Performance testing of the embodiments and comparative examples:

[0069] (1) SEM morphology of titanium alloy surface under different processing techniques:

[0070] Figure 1 SEM images of titanium alloy surfaces under different processing techniques. Figure 1 (a)- Figure 1 (c) SEM images of the polished TA24 sample, the MAO-TA24 (10 min) sample, and the MAO-TA24-hydrothermal treated sample, respectively.

[0071] Figure 1 (a) shows that the surface of the TA24 sample is relatively smooth after polishing.

[0072] Figure 1 (b) shows that after polishing and micro-arc oxidation treatment, the surface of the micro-arc oxidation coating of the MAO-TA24 sample (10 minutes) has a large number of micropores and microcracks.

[0073] Figure 1 (c) shows that after polishing, micro-arc oxidation and hydrothermal treatment, the MAO-TA24-hydrothermal treated sample forms nano-spiky surfaces and interiors on the porous surface. At this time, the coating surface of the titanium alloy is a porous and spiky surface.

[0074] (2) FTIR-ATR (Fourier Transform Infrared) spectra of titanium alloy surface coatings under different processing techniques:

[0075] Figure 2 FTIR-ATR (Fourier Transform Infrared) spectra of titanium alloy surface coatings under different processing techniques; Figure 2 The FTIR-ATR plots are shown for MAO-TA24 (10 min) sample and MAO-TA24-hydrothermal treated sample (Fig. a), DTT reagent and MAO-TA24-CUS complex sample (Fig. b), MAO-TA24-OH-p(AA-SBMA) / CS sample and MAO-TA24-OH-p(AA-SBMA) / CS-β-GPDN sample (Fig. c).

[0076] Figure 2 (a) Showing: The FTIR-ATR plot of MAO-TA24 is a straight line, indicating that a ceramic layer was formed on the micro-arc oxidation surface, while the MAO-TA24-hydrothermal treatment at 3231 cm⁻¹... -1 The presence of an absorption peak indicates that the porous burr surface of the titanium alloy contains a large number of -OH groups.

[0077] Figure 2 (b) shows that the FT-IR characteristic peaks of the MAO-TA24-CUS complex sample are the same as those of the ligand DTT. However, compared with the FT-IR of DTT, the MAO-TA24-CUS complex sample shows a different peak at 2554 cm⁻¹. -1 The disappearance of the SH stretching vibration peak indicates that Cu on the micro-arc oxidation surface... 2+ It reacted with the thiol group in dithiothreitol to form a Cu-S complex.

[0078] Figure 2 (c) Showing: FT-IR image of MAO-TA24-OH-p(AA-SBMA) / CS sample, 1750 cm⁻¹ -1 The decrease in absorption peak intensity at 1182 cm⁻¹ proves that the prepolymer and the hydrothermally treated surface are covalently linked by -OH and -OH bonds. -1 The absorption peak corresponds to the C–N tensile vibration in the PSBMA chain segment, at 1729 cm⁻¹. -1 The sharp single peak at 1039 cm⁻¹ confirms the presence of the carbonyl group. -1The absorption peak at 1483 cm⁻¹ indicates the presence of sulfonic acid groups. Other peaks are located at 1483 cm⁻¹. -1 At 962-526 cm -1 The peaks within the range are attributed to the vibrations of CH and C-C bonds in the polymer backbone. 3445 cm⁻¹ -1 The peak at 929 cm⁻¹ represents the stretching vibration of the hydroxyl group (-OH). -1 The bending vibration peak of -OH at the position can confirm the presence of -COOH, indicating the formation of the first network polymer p(AA-SBMA).

[0079] In the FT-IR spectrum of the MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample, new absorption peaks appeared. The broad peak at 3600-3000 cm⁻¹ is attributed to the stretching vibration of -OH groups. Chitosan contains a large number of hydroxyl groups, and saturated glycerol phosphate also contains hydroxyl groups. Their -OH stretching vibrations are superimposed, and the peak broadens due to interactions such as hydrogen bonding, resulting in a broad peak at 3600-3000 cm⁻¹. The peak at 2223-2074 cm⁻¹ is attributed to the stretching vibrations of some unsaturated bonds (C≡C, C≡N, etc.) or cumulative double bonds. This indicates that the amino groups of chitosan can form an ionic crosslinking network (MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN) with negatively charged phosphates through "binary" coordination bonds, thus resulting in the broad peak at 2223- An absorption peak appears at 2074 cm⁻¹. The high density of the "binary" coordination bonds results in greater network rigidity and better stability in water. During gel deformation, the ionic covalent network dissipates energy more easily, enhancing the toughness of the hydrogel.

[0080] (3) Pollution status of titanium alloy surfaces under different treatment processes after a 45-day test on marine sidings:

[0081] Figure 3 Figures showing the contamination status of titanium alloy surfaces after a 45-day test on marine sidings under different treatment processes. Figure 3 (a)-(c) show the results of the polished TA24 sample, MAO-TA24 (10 min) sample, and MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample, respectively.

[0082] Figure 3 (a) shows that after polishing, the surface of the TA24 sample was covered with a large amount of algae and large pollutants such as barnacles, resulting in poor anti-fouling effect.

[0083] Figure 3 (b) shows that the titanium alloy MAO-TA24 sample treated with micro-arc oxidation (10 minutes) has fewer barnacles on its surface, but more algae and tube worms.

[0084] Figure 3 (c) shows that after micro-arc oxidation, hydrothermal treatment and superhydrophobic treatment, the surface of the titanium alloy MAO-TA24-hydrothermal treatment-SHS sample did not have obvious barnacles and tube worms attached, and the surface dirt was mainly algae attached.

[0085] Figure 3 (d) shows that the titanium alloy MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample after micro-arc oxidation, hydrothermal treatment and hydrogel coating has no obvious fouling organisms on its surface, and the composite coating with hydrogel has excellent antifouling performance.

[0086] (4) Friction behavior of titanium alloy surfaces under different treatment processes in artificial seawater:

[0087] Figure 4 Stribeck curves of titanium alloy surfaces under different treatment processes in artificial seawater. Figure 4 The four lines in the image show the results of samples 1 through 4, corresponding to the polished TA24 sample, the MAO-TA24 (10 minutes) sample, the MAO-TA24 hydrothermal treated sample, and the MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample, respectively.

[0088] The friction curve testing process was as follows: Four different samples (sample 1: TA24; sample 2: MAO-TA24; sample 3: MAO-TA24-hydrothermal treated; sample 4: MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN)) were tested for friction performance using a reciprocating friction and wear testing machine. Sliding wear testing was conducted on a specific friction and wear testing machine, using 5mm diameter Si3N4 balls as the grinding material, which were reciprocated against the sample surface. During the test, the parameters were set as follows: constant load of 10N, oscillation stroke of 4mm, frequency of 2Hz, and sliding time of 0.5h (total sliding distance of 28.8m).

[0089] Figure 4 The black line indicates that the polished TA24 has a relatively smooth surface, but in the initial stage of friction, the friction coefficient fluctuates significantly due to processes such as surface atom adsorption, oxide film formation and destruction. As the friction process continues, the surface gradually reaches a dynamic equilibrium state, and the friction coefficient tends to stabilize. After 1800 seconds of testing, the friction coefficient of sample 1 reached 0.369.

[0090] Figure 4The red line indicates that the TA24 (MAO-TA24 sample) after micro-arc oxidation has a porous surface. At the beginning of friction, these pores affect the contact state between the grinding ball and the sample surface, causing fluctuations in the coefficient of friction. As friction progresses, the pores are smoothed or filled, the contact state gradually stabilizes, and the coefficient of friction also tends to stabilize. The porous structure allows it to store some lubricant or wear debris during friction; compared to sample 1, the final stable coefficient of friction is slightly lower. After 1800 s of testing, the coefficient of friction for sample 2 is 0.337.

[0091] Figure 4 The blue line indicates that the sample treated with sodium hydroxide hydrothermally (MAO-TA24 - hydrothermally treated sample) has a porous and needle-like surface morphology. This unique microstructure makes the contact between the sample and the grinding ball more stable, and the coefficient of friction remains essentially unchanged after the initial small fluctuations. The needle-like structure may play a role in supporting and stabilizing the contact, reducing relative sliding and changes in the coefficient of friction during the friction process. Compared to sample No. 2, its coefficient of friction is lower. After 1800s of testing, the coefficient of friction for sample No. 3 is 0.305.

[0092] Figure 4 The green line indicates that the titanium alloy MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN sample, after undergoing micro-arc oxidation, hydrothermal treatment, and hydrogel coating, exhibits lubrication and buffering effects during friction. Initially, the coefficient of friction fluctuates due to factors such as the wear-in of the coating and the grinding ball. Over time, the coating gradually develops a stable lubricating effect, reducing the fluctuations in the coefficient of friction and eventually stabilizing at a minimum value, lower than the other three samples. This is because the hydrogel effectively reduces the friction between the grinding ball and the sample surface, minimizing energy loss and surface damage during friction. After 1800 seconds of testing, the coefficient of friction for sample #4 was 0.283.

[0093] In summary, compared with the prior art, the method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates provided in this application includes the following design concepts and beneficial effects:

[0094] 1. Concept:

[0095] This application first employs micro-arc oxidation technology to treat titanium alloys, growing a dense and uniform ceramic film in situ on the surface of a titanium alloy substrate (e.g., a titanium alloy pipe). This film adheres firmly to the titanium alloy substrate, without interface defects, thus enhancing the stability and durability of the film. Subsequently, hydrothermal treatment technology alters the surface structure after micro-arc oxidation, introducing nanoscale microstructures and hydroxyl groups onto the ceramic film surface. This multi-level structure significantly increases its specific surface area, laying the foundation for subsequent adsorption and reaction of organic molecules. Dithiothreitol (DTT) also contains -SH (thiol) groups. In the above reaction, these thiol groups chemically react with copper ions on the surface of the hydrothermally treated titanium alloy to form Cu-S bonds, creating high-density covalent bonds. This results in a large number of hydroxyl groups on the surface. Utilizing covalent interactions and substrate anchoring effects (porous structure), this lays the foundation for high-strength adhesion between the hydrogel and the titanium alloy substrate. A coating is applied to the surface of a treated titanium alloy pipe. In the first network layer, under UV excitation, the C=C bonds in acrylic acid molecules and the C=C bonds in sulfobetaine undergo free radical polymerization. These free radicals initiate the opening of the C=C double bonds in sulfobetaine, which then connect with the double bonds of other acrylic acid molecules to form polymer chains. During polymerization, C-C covalent bonds are formed, contributing to the network structure. Sulfobetaine contains active groups (such as sulfonic acid groups), and acrylic acid (carboxylic acid groups, etc.) forms hydrogen bonds, thus participating in the network construction. The hydroxyl groups of chitosan interact with the active groups of other molecules through hydrogen bonding, further stabilizing the network structure. In the second network layer, the active groups such as phosphate groups in sodium glycerophosphate react with the active sites (amino groups of chitosan) in the first network layer. The phosphate groups form salt bonds with the amino groups of chitosan, thus building a second network on top of the first, forming a double-network hydrogel. Hydrogen bonds can be formed between the hydroxyl groups (-OH) in the hydrogel and the hydroxyl groups on the surface of the micro-arc oxidation layer. In the construction of multilayer structures, it can play a strong connecting role, enhancing the overall structural stability. For example, hydrogen bonds are formed between the -OH groups in the acrylic polymer chain and the -OH groups on the surface of the micro-arc oxidation layer, making the bond between the hydrogel layer and the micro-arc oxidation layer tighter. This dual-network hydrogel contains zwitterionic polymers, which can firmly bind water molecules through ionic solvation, forming a hydration layer physical barrier that effectively prevents the adhesion of other molecules and dirt and organisms.

[0096] Due to the unique electroneutrality of the zwitterions in the prepared MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN hydrogel, the possibility of marine mud particles adsorbing onto the hydrogel surface through ion coupling is avoided. Furthermore, the hydration layer formed by the zwitterions acts as a lubricant between the fluid and solid surfaces, transforming the direct contact between the fluid and solid surfaces into a liquid-liquid contact, thereby significantly reducing interfacial friction and achieving drag reduction for titanium alloy substrates used in seawater environments.

[0097] Innovations compared to existing hydrogel coatings: Micro-arc oxidation, hydrothermal treatment, dithiothreitol modification, and bilayer network hydrogel coating are combined. Micro-arc oxidation generates a ceramic layer in situ on the material surface, bonding firmly to the substrate. Hydrothermal treatment further optimizes the surface structure, while dithiothreitol modification enhances the chemical bond between the hydrogel and the underlying layer. Compared to ordinary hydrogel coatings, its bond with the antifouling surface is more stable and less prone to peeling. Surfaces treated with micro-arc oxidation and hydrothermal treatment exhibit improved hardness and wear resistance. The bilayer network hydrogel structure itself has good stability, better resisting erosion and damage from external environmental factors, extending the coating's service life. The bilayer network hydrogel has good hydrophilicity, effectively preventing the adhesion of dirt, while the multilayer structure and modification treatment further enhance its antifouling performance.

[0098] 2. The proposed solution has the following beneficial effects:

[0099] (1) The present application scheme enhances the mechanical properties of the coating and improves the stability and durability of the coating (MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN hydrogel) applied to the titanium alloy substrate, that is, the coating has long-term stable anti-fouling performance;

[0100] (2) A high bonding strength between the antifouling coating and the titanium alloy substrate was achieved;

[0101] (3) The coating (MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN hydrogel) applied to the titanium alloy substrate forms a hydration layer physical barrier, which can effectively prevent the adhesion of other molecules and dirt organisms. The coating applied to the titanium alloy substrate has excellent antifouling effect.

[0102] (4) The unique electronegativity of the zwitterionic ions in the prepared MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN hydrogel avoids the possibility of marine mud particles being adsorbed onto the surface of the hydrogel through ion coupling, thus giving the coating excellent antifouling effect.

[0103] (5) The zwitterionic hydration layer formed by the prepared MAO-TA24-OH-p(AA-SBMA) / CS-β-GP DN hydrogel plays a lubricating and drag-reducing role between the fluid and the solid surface, so that the coating has excellent drag-reducing effect.

[0104] It should be noted that:

[0105] Explanation of Stribeck's meaning: In the Stribeck curve, Stribeck uses the coefficient of friction m as the ordinate and (lubricant viscosity × sliding speed) / load as the abscissa to illustrate several lubrication methods. (This can be removed; the equipment has been changed, and this formula is no longer used.)

[0106] In this article, “~” is used to represent the range of values, and the range of values ​​represented by this expression includes two endpoint values.

[0107] The specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the concept of this application, and are not intended to limit them; those skilled in the art can make adaptive adjustments within the concept and protection scope of this application.

[0108] In addition, unless otherwise specified, the raw materials used may be commercially available products in the field or prepared by conventional methods in the field; that is, the reagents and instruments used in this embodiment do not specify the manufacturer or other information, and are all conventional products that can be purchased from the market.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a coating with high adhesion, antifouling properties, and drag reduction for titanium alloy substrates, characterized in that, Includes the following steps: Micro-arc oxidation: Micro-arc oxidation is performed on titanium alloys to form a ceramic film on the surface of the titanium alloys; Hydrothermal treatment: The titanium alloy after micro-arc oxidation is subjected to a hydrothermal reaction to introduce nanoscale porous thorn microstructures and hydroxyl groups on the surface of the ceramic film; Hydrogel coating: The prepolymer is coated onto the hydrothermally treated titanium alloy, and the reaction is carried out under ultraviolet light to obtain the first network gel, which is the coating. After the first network gel is formed, the first network gel is post-treated; the post-treatment process is as follows: the first network gel is immersed in a β-glycerophosphate sodium salt solution to form an ion-covalent double network p(SBMA-co-AAc) / CS-β-GP DN hydrogel; The prepolymer liquid is a slightly yellow, viscous liquid formed by reacting a mixture at room temperature under a protective atmosphere; the mixture is a mixed solution formed by mixing chitosan, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, α-ketoglutaric acid, and acrylic acid in water. The preparation process of the prepolymer liquid is as follows: Chitosan and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide were dissolved in water to form a mixture; then α-ketoglutaric acid and acrylic acid were added to the mixture and reacted at room temperature for 10-20 minutes under a nitrogen atmosphere to obtain a slightly yellow viscous liquid. Finally, the air bubbles in the slightly yellow viscous liquid were eliminated to obtain a prepolymer solution. In the mixture, the mass ratio of chitosan to water is 1 to 10:100, and the molar concentration of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 1 mol / L to 5 mol / L. The molar ratio of α-ketoglutaric acid to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 0.1 to 2:100; the molar ratio of acrylic acid to [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide is 1 to 10:

100.

2. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 1, characterized in that: The prepolymer solution was coated onto a hydrothermally treated titanium alloy and reacted under ultraviolet light for 7–12 h to obtain a first network gel. The first network gel was then immersed in a β-glycerophosphate sodium salt solution for 0.5–8 h to form an ion-covalent double network p(SBMA-co-AAc) / CS-β-GP DN hydrogel.

3. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 1, characterized in that, The micro-arc oxidation process is as follows: an electrolyte is placed in an electrolytic cell, and then a titanium alloy is placed in the electrolyte as an anode, and a metal sheet in the electrolytic cell is used as a cathode. The bipolar pulse micro-arc oxidation power supply was activated to perform micro-arc oxidation treatment; then the titanium alloy was cleaned. In this process, the electrolyte temperature is kept below 20℃ throughout the micro-arc oxidation treatment, and a constant current mode is used with a current density of 0.5–2 mA / cm². 2 The frequency is 300–2000 Hz, the duty cycle is 3–10%, the deposition time is 300–1200 s, and the termination voltage is 400–650 V.

4. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 3, characterized in that... The electrolyte comprises silicates, glycerol, potassium fluoride, phosphates, sodium hydroxide, and water. In the electrolyte, the concentrations of silicate, glycerol, potassium fluoride, phosphate and sodium hydroxide are 5-15 g / L, 3-9 g / L, 0-10 g / L, 0-5 g / L and 5-15 g / L, respectively. The metal sheet is made of stainless steel.

5. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 1, characterized in that, The hydrothermal reaction process is as follows: The titanium alloy after micro-arc oxidation treatment is immersed in an alkaline solution preheated to 20-60°C for 0.5-4 hours. Then, the titanium alloy is removed and immersed in a dithiothreitol dilution solution. The pH of the dithiothreitol dilution solution is adjusted to 6-6.5 with alkali and stirred at room temperature for 10-60 minutes to introduce nanoscale microstructures and hydroxyl groups onto the surface of the ceramic film.

6. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 5, characterized in that: During the hydrothermal reaction, sodium hydroxide was used to adjust the pH of the dithiothreitol dilution. The alkaline solution is a 1-8 wt% sodium hydroxide aqueous solution; the molar concentration of the dithiothreitol dilution is 0.01-0.05 mol / L; After the hydrothermal reaction is completed, the titanium alloy is removed and stored at low temperature for later use.

7. The method for preparing a high-adhesion, anti-fouling, and drag-reducing coating for titanium alloy substrates according to claim 1, characterized in that, Before the micro-arc oxidation treatment, the surface of the titanium alloy is polished and cleaned in sequence.

8. A coating for high adhesion, anti-fouling, and drag-reducing properties on titanium alloy substrates, characterized in that: It is prepared by the preparation method described in any one of claims 1-7.

9. The application of the coating with high adhesion, antifouling and drag reduction for titanium alloy substrates as described in claim 8 on the surface of titanium metal structures.

Images