Preparation method of self-repairing AO-CuAl-LDH-Ce composite film based on anodic oxidation

Abstract

The invention provides a preparation method of a self-repairing AO-CuAl-LDH-Ce composite film based on anodic oxidation, and belongs to the technical field of metal surface treatment and anti-corrosion protection materials. According to the method, aluminum alloy serves as a base body, firstly, an oxidation film with a porous structure is formed on the surface of the aluminum alloy through anodic oxidation to serve as a rough substrate, then CuAl layered double hydroxides grow in situ in pore channels and the surface of the anodic oxidation film through a hydrothermal reaction under the alkaline condition, cerium salt is introduced in the growth process, and the CuAl layered double hydroxides are obtained. Doping and deposition of cerium elements between LDH layers and on the surface are achieved, and the AO-CuAl-LDH (at) Ce composite film with the self-repairing function is constructed. The prepared composite film is composed of a porous anodic oxide layer, a CuAl-LDH barrier layer and a cerium-based compound self-repairing layer, and has good bonding strength, excellent corrosion resistance and self-repairing capacity after damage. The method is simple in process, controllable in parameter, suitable for long-acting protection of aluminum and aluminum alloy components and good in industrial application.

Description

Technical Field

[0001] This invention belongs to the technical field of metal surface treatment and anti-corrosion materials, specifically relating to a method for preparing a self-healing AO-CuAl-LDH@Ce composite film based on anodic oxidation. Background Technology

[0002] Aluminum and aluminum alloys are widely used in aerospace, transportation, and marine engineering due to their low density, high specific strength, and excellent processing properties. However, under chlorine-containing media, humid and hot environments, and friction-induced service conditions, aluminum alloys are prone to pitting corrosion, crevice corrosion, and wear failure, which seriously affects their service life.

[0003] Anodizing, as a mature surface treatment process, can form a porous alumina film that is metallurgically bonded to the substrate on the surface of aluminum and aluminum alloys, exhibiting certain corrosion resistance and wear resistance. However, traditional anodized films have interconnected pores, offering limited barrier properties and making them unsuitable for long-term service in harsh corrosive environments.

[0004] Layered double hydroxides (LDHs) are a class of anionic clay materials with a two-dimensional layered structure. They possess excellent ion exchange capacity, barrier properties, and corrosion inhibition properties, and are considered highly promising metal protective materials. Among them, CuAl-LDH exhibits superior corrosion resistance and chemical stability compared to the more common MgAl-LDH and ZnAl-LDH.

[0005] To further improve the protective performance of LDH films, we attempted to introduce rare earth elements for modification. Ce element, due to its Ce... 3+ / Ce 4+ Reversible redox properties allow for preferential deposition of oxides or hydroxides at corrosion defects, resulting in excellent corrosion inhibition and self-healing capabilities. However, existing LDH films are mostly prepared by coating or single-step hydrothermal methods, which have limited adhesion to the metal substrate, and the introduction of Ce is complex, making it difficult to achieve a stable and uniform in-situ composite structure.

[0006] Therefore, how to utilize the porous and rough structure of anodic oxide film as a growth substrate to achieve in-situ dense growth of CuAl-LDH, and synergistically introduce cerium to construct a composite film with both barrier and self-healing functions, is a key technical problem that urgently needs to be solved. Summary of the Invention

[0007] This invention addresses the problems of insufficient adhesion between coatings and substrates, limited protective functions, weak self-healing capabilities, and complex processes in existing aluminum and aluminum alloy surface protection technologies. It provides a method for preparing a self-healing AO-CuAl-LDH@Ce composite film based on anodic oxidation.

[0008] The present invention is implemented as follows: A method for preparing a self-healing AO-CuAl-LDH@Ce composite film based on anodizing includes the following steps: (1) Substrate pretreatment: The aluminum alloy substrate is pretreated by mechanical grinding, degreasing, pickling and alkaline etching to obtain a clean and activated metal surface; (2) Anodizing to construct a rough interface: The substrate after step (1) is placed in an electrolyte for anodizing treatment to form an anodized film with a porous structure on the substrate surface to construct a rough interface; (3) In-situ growth of CuAl-LDH: The anodized substrate is immersed in a Cu-containing electrolyte. 2+ The alkaline reaction solution of the precursor is subjected to hydrothermal reaction to allow CuAl layered double hydroxide (CuAl-LDH) to grow in situ on the pores and surface of the anodic oxide film, thus obtaining an AO-CuAl-LDH composite film; (4) Introduction of cerium and construction of self-repairing structure: During the growth of CuAl-LDH, by introducing Cu-containing elements into the anodic oxide film, CuAl-LDH layered double hydroxide (CuAl-LDH) is grown in situ on the pores and surface of the anodic oxide film; (5) Introduction of cerium and construction of self-repairing structure: During the growth of CuAl-LDH, CuAl-LDH layered double hydroxide (CuAl-LDH) is grown in situ on the pores and surface of the anodic oxide film, thus obtaining an AO-CuAl-LDH composite film; 2+ Cerium salt is introduced into the alkaline reaction solution of the precursor, allowing cerium to enter the LDH interlayer and deposit on its surface to form cerium-based compounds, thereby preparing an AO-CuAl-LDH@Ce composite film with self-healing function.

[0009] Preferably, the process further includes step (5) hydrophobic modification treatment: using a hydrophobic agent to modify the obtained AO-CuAl-LDH@Ce composite film with a low surface energy material to achieve superhydrophobic surface properties. More preferably, the hydrophobic agent in step (5) is a silane-based hydrophobic agent. More preferably, the hydrophobic modification treatment process in step (5) includes the following steps: S1, preparing a silane-based hydrophobic agent and stirring it in a water bath at 40-60℃ for 1-2 hours to ensure uniform mixing of all components; S2, immersing the AO-CuAl-LDH@Ce composite film obtained in step (4) in a hydrophobic agent at 40-50℃ for 2-4 hours; S3, drying the hydrophobically treated AO-CuAl-LDH@Ce composite film in a vacuum drying oven at 60-80℃ for 1-2 hours to obtain a superhydrophobic AO-CuAl-LDH@Ce composite film.

[0010] Preferably, step (2) of constructing a rough interface by anodizing includes the following steps: S1, using the substrate as the anode, the graphite plate as the cathode, and a mixture of sulfuric acid and aluminum sulfate as the electrolyte, wherein the concentration of sulfuric acid in the electrolyte is 160-170 g / L and the concentration of aluminum sulfate is 0.4-0.6 g / L; S2, controlling the anodizing current density to be 1.2-1.5 A / dm², the reaction temperature to be 20±1℃, and the oxidation time to be 20-40 min; S3, after the anodizing is completed, the sample is taken out, thoroughly rinsed with deionized water to remove residual electrolyte, and naturally dried under cold air conditions to obtain an anodized film with a porous structure on the surface.

[0011] Preferably, in the in-situ growth of CuAl-LDH in step (3), the alkaline reaction solution is a mixture of 0.1 mol / L Cu(NO3)2·6H2O and 0.05 mol / L NaNO3, and the pH of the mixture is adjusted to 10.8-11.2 using 2 mol / L NaOH solution.

[0012] Preferably, the hydrothermal reaction in step (3) is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, and the hydrothermal reaction is carried out at 140-160℃ for 4-6 hours. After the reaction is completed, the sample is naturally cooled to room temperature, taken out, thoroughly rinsed with deionized water and dried to obtain AO-CuAl-LDH composite film.

[0013] Preferably, the Cu / Al molar ratio in the reaction system in step (3) is 1.5-3.0.

[0014] Preferably, step (1) of substrate pretreatment includes the following processes: S1 Mechanically polishing the substrate surface with silicon carbide sandpaper to make the surface smooth and uniform; S2 Ultrasonic cleaning of the polished substrate in acetone and anhydrous ethanol to remove surface oil stains, and then rinsing with deionized water; S3 Immersing the cleaned substrate in dilute sulfuric acid solution for acid washing to remove the natural oxide film, and then rinsing with deionized water; S4 Alkali etching of the substrate in NaOH solution to further activate the surface, and finally cleaning with deionized water and ethanol and drying.

[0015] The beneficial effects of the present invention are as follows: (1) Significantly improves the bonding strength between the composite film and the substrate. The present invention constructs a rough interface with a porous structure on the surface of aluminum and aluminum alloys through anodizing. The oxide film formed is metallurgically bonded to the substrate. CuAl-LDH grows in situ in the pores and on the surface of the anodized film, forming a composite structure of "pore interlocking-surface covering", which enables a stable mechanical interlocking effect between the functional film and the substrate, effectively avoiding the problem of easy peeling of traditional coated LDH films. (2) Achieves multi-level synergistic protection and significantly improves corrosion resistance. The AO-CuAl-LDH@Ce composite film constructed by the present invention consists of a bottom porous anodized film, a middle CuAl-LDH barrier layer and a surface cerium-based compound layer. The three work together to form a multi-level protective structure. Among them, the anodized film provides a basic barrier, the CuAl-LDH layer effectively blocks the penetration of corrosive media, and the cerium-based compound layer further inhibits the corrosion reaction through active corrosion inhibition, making the corrosion resistance of the composite film significantly better than that of a single anodized film or a single LDH film. (3) Endows the composite film with self-healing function and improves service reliability. Cerium has Ce 3+ / Ce 4+ Reversible redox properties: When local defects or microcracks appear in the composite film during service, cerium ions can migrate to the defect area and preferentially deposit to form cerium-based oxides or hydroxides, effectively filling and sealing the defects, thereby delaying corrosion propagation and realizing the self-repair protection of the composite film. (4) CuAl-LDH has a stable structure and long-lasting protective performance. Compared with common MgAl-LDH or ZnAl-LDH, CuAl-LDH has higher structural stability and corrosion resistance. Its layered structure is not easy to dissolve or collapse in the corrosive environment, ensuring the stability of the protective performance of the composite film during long-term service. (5) Clear process route, controllable parameters, suitable for industrial application. This invention adopts a process route combining anodic oxidation and hydrothermal in-situ growth. The steps are simple, the process is mature, the controllable range of each key parameter is wide, the repeatability is good, and it is easy to promote and apply on existing aluminum alloy surface treatment production lines. (6) Strong substrate adaptability and wide application range. The method of this invention is applicable to a variety of aluminum and aluminum alloy substrates, has strong adaptability to substrate composition, does not rely on high-purity raw materials or special alloy design, and can be widely used in aerospace, automobile manufacturing, marine engineering and equipment structural components. (7) The protection mechanism is clear and the comprehensive performance is excellent. This invention provides a new technical solution for long-term protection of aluminum and aluminum alloy surfaces by synergistically working through multiple protection mechanisms of "mechanical anchoring-physical barrier-chemical self-healing", taking into account bonding strength, corrosion resistance and service reliability. Attached Figure Description

[0016] Figure 1Comparison of SEM images at different magnifications for anodic oxidation (AO) (ac), AO-CuAl-LDH (df), and AO-CuAl-LDH@Ce (gi) in Example 1.

[0017] Figure 2 (a) and Figure 2 (b) Comparison of XRD images and magnified views of 2219Al, AO-CuAl-LDH, and AO-CuAl-LDH@Ce in Example 1.

[0018] Figure 3 (a) Figure 3 (b) Figure 3 (c) and Figure 3 (d) are the contact angle test data of 2219Al, AO, AO-CuAl-LDH, and AO-CuAl-LDH@Ce in Example 1, respectively.

[0019] Figure 4 This is a schematic diagram illustrating the dynamic low adhesion process of water droplets on AO-CuAl-LDH in Example 1, wherein... Figure 4 (a) shows water droplets contacting the AO-CuAl-LDH surface. Figure 4 (b) The rebound of a water droplet on the AO-CuAl-LDH surface. Figure 4 (c) shows a water droplet bouncing on the AO-CuAl-LDH surface; Figure 4 (d) is the contact angle of the water droplet that finally lands on the AO-CuAl-LDH surface.

[0020] Figure 5 These are test photos of the coating self-cleaning process at each stage in Example 1, where... Figure 5 (a1-a4) represents the dynamic changes in the contact between the water flow and the pencil powder on the AO over time; Figure 5 (b1-b4) represents the dynamic changes in the contact between the water flow and the pencil powder on AO-CuAl-LDH over time; Figure 5 (c1-c4) represents the dynamic changes in the contact between the water flow and the pencil powder on AO-CuAl-LDH@Ce over time.

[0021] Figure 6 (a) and Figure 6 (b) are photographs of the adhesion test at different locations of the AO-CuAl-LDH@Ce film obtained in Example 1.

[0022] Figure 7 The graph shows the electrochemical performance test results of the coatings at each stage in Example 1 in a 3.5wt% NaCl solution. Figure 7(a) Representative polarization curves of 2219Al, AO, AO-CuAl-LDH, and AO-CuAl-LDH@Ce in 3.5wt% sodium chloride aqueous solution; Figure 7 (b) Nyquist plots of 2219Al, AO, AO-CuAl-LDH, and AO-CuAl-LDH@Ce; Figure 7 (c) represents the impedance modulus of 2219Al, AO, AO-CuAl-LDH, and AO-CuAl-LDH@Ce at a low frequency of 0.01Hz (|Z| 0.01Hz). Figure 7 (d) High-frequency phase angles of 2219Al, AO, AO-CuAl-LDH, and AO-CuAl-LDH@Ce; Figure 7 (e) is the equivalent circuit model established by fitting the electrochemical impedance spectroscopy data of 2219Al and AO; Figure 7 (f) is the equivalent circuit model established by fitting the electrochemical impedance spectroscopy data of AO-CuAl-LDH and AO-CuAl-LDH@Ce.

[0023] Figure 8 The images show the 3D morphology of the AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coatings obtained in Example 1 after wear, and the 3D morphology after immersion in a 3.5wt% NaCl solution for 24 hours following wear. Figure 8 (a) and Figure 8 (b) Wear 3D morphology of AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coatings, respectively; Figure 8 (c) and Figure 8 (d) are 3D morphology images of AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coatings after wear and immersion in 3.5wt% NaCl solution for 24 hours.

[0024] Figure 9 These are friction test images of the coatings prepared at each stage in Example 1, wherein... Figure 9 (a) is the coefficient of friction. Figure 9 (b) is the average coefficient of friction. Figure 9 (c) represents the wear rate; Figure 9 (d) Images of wear tracks obtained on the surface.

[0025] Figure 10 The potential dynamics polarization curves, Nyquist plots, Bode modulus plots, and Bode phase angle plots of the coatings prepared in each stage of Example 1 were obtained after immersion in a 3.5wt% NaCl solution for 24 hours under tribo-wear conditions. Figure 10 (a) shows the potential dynamics polarization curve; Figure 10 (b) is the Nyquist plot; Figure 10(c) is the Bode modulus diagram; Figure 10 (d) is the Bode phase angle diagram. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0027] Example 1

[0028] A method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation includes the following steps:

[0029] (1) Substrate pretreatment: The 2219 aluminum alloy sheet was cut into a substrate with a size of Φ14mm×3mm. The substrate was pretreated by mechanical grinding, degreasing, pickling and alkaline etching to obtain a clean and activated metal surface. The specific treatment process is as follows: S1. The substrate surface was mechanically ground with 400#, 800#, 1000#, 1500# and 2000# silicon carbide sandpaper to make the surface flat and uniform; S2. The pretreated substrate was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface oil, and then rinsed with deionized water; S3. The cleaned substrate was immersed in dilute sulfuric acid solution for pickling to remove the natural oxide film, and then rinsed with deionized water; S4. The sample was then immersed in NaOH solution for alkaline etching to further activate the surface, and finally cleaned with deionized water and ethanol and dried.

[0030] (2) Constructing a rough interface through anodizing: The substrate treated in step (1) is placed in an electrolyte for anodizing treatment to form an anodized film with a porous structure on the substrate surface, thereby constructing a rough interface. The specific process includes the following steps: S1, using the substrate as the anode, a graphite plate as the cathode, and a mixture of sulfuric acid and aluminum sulfate as the electrolyte, wherein the concentration of sulfuric acid in the electrolyte is 170 g / L and the concentration of aluminum sulfate is 0.45 g / L; S2, controlling the anodizing current density to be 1.5 A / dm², the reaction temperature to be 20 ± 1 °C, and the oxidation time to be 30 min; S3, after the anodizing is completed, the sample is taken out, thoroughly rinsed with deionized water to remove residual electrolyte, and naturally dried under cold air conditions to obtain an anodized film with a porous structure on the surface.

[0031] (3) In-situ growth of CuAl-LDH: The anolyzed matrix is ​​immersed in CuAl-LDH. 2+An alkaline reaction solution of the precursor is used to induce in-situ growth of CuAl layered double hydroxide (CuAl-LDH) in the pores and surface of the anodic oxide film via a hydrothermal reaction, resulting in an AO-CuAl-LDH composite film. The Cu / Al molar ratio in the CuAl layered double hydroxide is 1.5. The alkaline reaction solution is a mixture of 0.1 mol / L Cu(NO3)2·6H2O and 0.05 mol / L NaNO3, with the pH adjusted to 10.8 using a 2 mol / L NaOH solution. The hydrothermal reaction is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner at 140°C for 6 hours. After the reaction, the sample is allowed to cool naturally to room temperature, removed, thoroughly rinsed with deionized water, and dried in a vacuum drying oven at 80°C to obtain the AO-CuAl-LDH composite film.

[0032] (4) Introduction of cerium and construction of self-healing structure: During the growth of CuAl-LDH, cerium is introduced into Cu-containing structures... 2+ A 0.064 mol / L cerium nitrate (Ce(NO3)3·6H2O) solution was introduced into the alkaline reaction solution of the precursor, allowing cerium to enter the LDH interlayer and deposit on its surface to form cerium-based compounds, thereby preparing an AO-CuAl-LDH@Ce composite film with self-healing function.

[0033] (5) Superhydrophobic treatment: The obtained AO-CuAl-LDH@Ce composite film is modified with a low surface energy material using a hydrophobic agent to achieve superhydrophobic surface properties. The specific process includes the following steps: S1, prepare a hydrophobic agent by mixing hexadecyltrimethoxysilane, water and ethanol in a weight ratio of 3:1:16, and stir in a water bath at 60°C for 1 hour to ensure uniform mixing of each component; S2, immerse the AO-CuAl-LDH@Ce composite film obtained in step (4) in a hydrophobic agent at 50°C for 3 hours; S3, dry the hydrophobic treated AO-CuAl-LDH@Ce composite film in a vacuum drying oven at 80°C for 1 hour to obtain a superhydrophobic AO-CuAl-LDH@Ce composite film.

[0034] In this embodiment, the surface morphology of the substrate at each stage in the preparation of the self-healing AO-CuAl-LDH@Ce composite film based on anodic oxidation is as follows: Figure 1 As shown, where, Figure 1 (ac) are SEM images at different magnifications after anodizing. The surface of the aluminum alloy is completely covered with many thin plate-like hydroxides. The pores are filled with hydroxide deposits from bottom to top, but many micron-sized pores remain on the surface. Porous alumina is generated on the surface of the 2219 aluminum alloy substrate. Due to its porous structure, it has limited resistance to corrosive solutions in the corrosive environment. Figure 1(df) are SEM images of AO-CuAl-LDH at different magnifications. It can be seen that the growth of LDH covers the porous oxide film generated by anodic oxidation and generates a densely packed CuAl-LDH composite film layer on the oxide film surface. The fine cracks seen after magnification are microcracks caused by the growth stress of the LDH film layer when it grows on the surface of the AO oxide film. Figure 1 (gi) are SEM images of AO-CuAl-LDH@Ce at different magnifications. It can be seen that the introduction of Ce has a higher reactivity in the crystallization of the LDH structure, and the nanosheets on the surface are more densely packed. This is formed by the synergistic organization of intercalated anion and cationic metal hydroxide layers.

[0035] Figure 2 The images shown are XRD patterns and magnified views of AO-CuAl-LDH and AO-CuAl-LDH@Ce in this embodiment. The characteristic diffraction peaks at 5.49° (003) and 11.62° (006) indicate that all samples are single-phase AO-CuAl-LDH. Compared to AO-CuAl-LDH, the characteristic diffraction peaks of LDH in AO-CuAl-LDH@Ce shift to a lower 2θ angle and a larger d-interval, which is due to the incorporation of Ce, an ion with a larger radius. 3+ (Al) 3+ 0.67Å, Ce 3+ (1.02 Å). Furthermore, the diffraction peak intensity of LDH in AO-CuAl-LDH@Ce is higher, which is due to the incorporation of Ce, which promotes LDH growth. The characteristic diffraction peaks of CeO2 in AO-CuAl-LDH@Ce appear at 17.32, 27.36, and 34.06, belonging to the (110), (111), and (200) crystal planes, respectively, confirming the successful Ce doping.

[0036] Figure 3 The contact angle (CA) test results at each stage of coating preparation in Example 1 show that the contact angle of the 2219 aluminum alloy substrate was 85.0°, indicating its hydrophilic properties. After hydrothermal treatment, the contact angle of the sample decreased significantly, which was caused by the increase in surface roughness and the formation of hydrophilic oxides. After CuAl layered double hydroxide growth, introduction of cerium, and hydrophobic treatment, the contact angle of the coating increased significantly, reaching 162.8°, proving that the coating has excellent superhydrophobic properties. This also demonstrates that the superhydrophobic surface has good anti-stick properties, and water droplets are not easily adhered to the surface.

[0037] Figure 4This is a schematic diagram illustrating the dynamic low adhesion process of water droplets on the AO-CuAl-LDH superhydrophobic coating in Example 1. After the water droplet is extruded from the test tube, it slowly contacts the AO-CuAl-LDH surface as the tube descends. During the slow ascent of the test tube, the spherical shape of the droplet undergoes stretching deformation, and a noticeable droplet bouncing phenomenon is observed. At this point, the adhesion between the test tube and the water droplet is greater than the adhesion between the droplet and the AO-CuAl-LDH surface. The final contact angle of the water droplet on the surface is 169.6 ± 2.1°, further demonstrating the superhydrophobic properties of the coating.

[0038] Figure 5 These are photographs of the coating self-cleaning process test at each stage in Example 1. To test the self-cleaning performance of the composite coating, black pencil powder was used as a contaminant on the coating surface. Figure 5 (a1-a4) represents the dynamic change in the contact between the water flow and the pencil powder on the AO over time. Figure 5 As shown in (a1-a4), water droplets rapidly mix with pencil powder on the AO coating, and the pencil powder cannot be washed away, indicating that the bare 2219 aluminum alloy substrate is hydrophilic after anodizing. Conversely, Figure 5 (b1-b4) represents the dynamic changes in the contact between the water flow and the pencil powder on the AO-CuAl-LDH over time. Figure 5 (c1-c4) represents the dynamic changes in the contact between water flow and pencil powder on AO-CuAl-LDH@Ce over time. It can be seen that when water is applied to the AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coating, the pencil powder is successfully washed away, leaving no residue or wet marks on the coating surface. These results demonstrate that the superhydrophobic film possesses excellent self-cleaning properties.

[0039] Figure 6 (a) and Figure 6 (b) Photographs showing the adhesion test results of the AO-CuAl-LDH@Ce composite film obtained in Example 1 at different locations. The adhesion of the superhydrophobic film prepared according to ATSM D3359-97 standard to the substrate was evaluated by a tape peel test, combined with strength testing. In a typical procedure, the lattice pattern was obtained by making two perpendicular cuts using a special knife (QFH-HG600, Guangdong). The transparent tape was pressed against the cut surface with a finger for 120 seconds to ensure good contact, and then peeled off. It can be seen that... Figure 6 (a) and Figure 6 (b) The adhesion between the AO-CuAl-LDH@Ce composite film and the substrate is close to the 5B level, indicating good adhesion to the substrate.

[0040] Figure 7The graphs show the electrochemical performance of the coatings at each stage in Example 1 in a 3.5 wt% NaCl solution. Figure 7 (a) Representative polarization curves of different samples (2219Al, AO, AO-CuAl-LDH, AO-CuAl-LDH@Ce) in 3.5wt% sodium chloride aqueous solution are shown to determine their corrosion resistance. Figure 7 (a) The fitting corrosion parameters of the polarization curves are shown in Table 1. Compared with the aluminum substrate, the corrosion potentials of AO and AO-CuAl-LDH increased from -0.72V to -0.73V and then to -0.18V. corr The value ranges from 33.88 μA·cm -2 Decreased to 14.13 μA·cm -2 Then to AO-CuAl-LDH I corr =0.31μA·cm -2 Then to AO-CuAl-LDH@Ce I corr =2.34×10 -3 μA·cm -2 The largest decrease was nearly four orders of magnitude, which means that AO-CuAl-LDH@Ce has the best corrosion protection effect. Figure 7 (b) is the Nyquist plot, from Figure 7 (b) It can be seen that the Nyquist plot of the AO-CuAl-LDH@Ce composite film contains a larger radius capacitance ring, indicating that it has the best corrosion resistance. The impedance modulus at a low frequency of 0.01Hz (|Z| 0.01Hz) is an important parameter revealing the corrosion resistance performance of the coating, such as... Figure 7 As shown in (c), the bare 2219 matrix has the smallest |Z| modulus, while the CuAl-LDH@Ce sample has the largest |Z| modulus, which is 3.885 × 10⁻⁶ for 2219. 2 Ω·cm 2 Increased to 6.26 × 10⁻⁶ for AO 2 Ω·cm 2 To AO-CuAl-LDH 6.616×10 4 Ω·cm 2 Then, AO-CuAl-LDH@Ce has a 6.727×10⁻⁶ 8 Ω·cm 2 This represents an improvement of 1 to 6 orders of magnitude. This is consistent with the Nyquist results, indicating that the composite coating exhibits excellent corrosion resistance. The high-frequency phase angle is a key parameter for evaluating the corrosion resistance of the coating, such as... Figure 7 As shown in (d), a higher phase angle generally indicates better protective performance, confirming that the AO-CuAl-LDH@Ce superhydrophobic coating has superior barrier performance. The equivalent circuit model established by fitting the electrochemical impedance spectroscopy data of 2219Al and AO is shown below. Figure 7 As shown in (e), the equivalent circuit model established by fitting the electrochemical impedance spectroscopy data of AO-CuAl-LDH and AO-CuAl-LDH@Ce is as follows: Figure 7 As shown in (f), Figure 7 (e) and Figure 7 (f) The fitted EIS data are shown in Table 2. The higher the Rct value, the better the corrosion resistance of the sample. The Rct value of the AO-CuAl-LDH@Ce sample is 7.68 × 10⁻⁶. 7 Ω·cm 2 This indicates that the superhydrophobic composite coating can effectively slow down the corrosion process.

[0041] Table 1. Fitting corrosion parameters of coating polarization curves at each stage in Example 1

[0042]

[0043] Table 2. EIS fitting parameters of coatings at each stage in Example 1

[0044]

[0045] Figure 8 The images show the 3D morphology of the AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coatings obtained in Example 1 after wear, and the 3D morphology after immersion in a 3.5wt% NaCl solution for 24 hours following wear. Figure 8 (a) and Figure 8 (b) Wear 3D morphology of AO-CuAl-LDH and AO-CuAl-LDH@Ce composite coatings, respectively; Figure 8 (c) and Figure 8 (d) 3D morphology images of AO-CuAl-LDH and AO-CuAl-LDH@Ce coatings after wear and immersion in 3.5wt% NaCl solution for 24 hours. From Figure 8 It can be seen that the AO-CuAl-LDH@Ce coating exhibits the least wear damage and remains relatively intact and uniform, indicating that the introduction of Ce enhances the mechanical stability and wear resistance of the coating. In contrast, the AO-CuAl-LDH coating without Ce shows more obvious material removal and surface undulations during the wear process. This difference can be attributed to the modulation effect of Ce ions on the LDH layer structure. Corrosion products are visible at the wear scratches of the AO-CuAl-LDH@Ce coating, covering part of the wear traces, showing a certain self-repair and barrier effect.

[0046] Figure 9 These are friction test images of the coatings prepared at different stages in Example 1. Figure 9 (a) is the coefficient of friction. Figure 9(b) is the average coefficient of friction. Figure 9 (c) represents the wear rate; Figure 9 (d) Images of wear tracks obtained from the surface. Figure 9 (b) The average friction coefficient shows that the friction coefficient of 2219 aluminum alloy is 0.85, which increases to 0.6 for AO-CuAl-LDH, and then to 0.5 for AO-CuAl-LDH@Ce. It can be inferred that LDH provides an effective protective layer for the matrix, while the doping of Ce ions can cause lattice distortion, generate more interlayer defects or weak bonding regions, and thus make it easier for interlayer slip to occur, reducing energy loss during the friction process and further reducing its friction coefficient. Figure 9 (c) shows the wear rate of the film, with the average wear rate of AO-CuAl-LDH being 51.39 μm. 2 / N·mm) is the average wear rate of AO-CuAl-LDH@Ce (23.75μm). 2 This is twice the amount of Ce ions (N·mm), indicating that the introduction of Ce ions is beneficial for improving the wear resistance of the coating. From Figure 9 (d) It can be seen that the wear depth of AO-CuAl-LDH is much greater than that of the AO-CuAl-LDH@Ce coating. Analysis shows that Ce... 3+ The introduction of [a certain substance] can partially replace Cu. 2+ Or Al 3+ By altering the charge density of the laminations, the distribution and arrangement of anions between the layers can be adjusted. This adjustment of charge balance may weaken interlayer forces, promote interlayer slip, and reduce shear resistance. During friction, Ce can be oxidized to CeO2, which has excellent lubricating properties. CeO2 nanoparticles can form a uniform transfer film on the friction surface, reducing direct contact between metals and thus reducing adhesive friction.

[0047] Figure 10 After the coatings prepared in each stage of Example 1 were immersed in 3.5wt% NaCl solution for 24 hours, the potential dynamics polarization curves, Nyquist plots, Bode modulus plots, and Bode phase angle plots under tribo-wear conditions are shown below. Figure 10 (a) Figure 10 (b) Figure 10 (c) and Figure 10 As shown in (d). The corrosion resistance performance of the 2219 substrate after friction and wear was used to evaluate the self-healing performance of the film in a corrosive environment after damage. Electrochemical analysis after the friction and wear experiment showed that the in-situ film still exhibited good corrosion resistance. Among them, the sample with Ce ions introduced showed the best corrosion resistance, which was almost unaffected by the film damage. This indirectly confirms the self-healing performance of the film after the introduction of Ce ions and its self-protection of the substrate. Figure 10 (a) E values ​​of fitted 2219Al, AO-CuAl-LDH, and AO-CuAl-LDH@Cecorr and I corr The values ​​are shown in Table 3; Figure 10 (b) Figure 10 (c) and Figure 10 (d) The fitted data are shown in Table 4.

[0048] Table 3. Fitting data of potential kinetic polarization curves of 2219Al, AO-CuAl-LDH and AO-CuAl-LDH@Ce in Example 1

[0049]

[0050] Table 4. Nyquist plot, Bode modulus plot, and Bode phase angle plot fitting data for each stage of the coating in Example 1.

[0051]

[0052] Example 2

[0053] A method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation includes the following steps:

[0054] (1) Substrate pretreatment: The 6061 aluminum alloy sheet was cut into a substrate with a size of Φ14mm×3mm. The substrate was pretreated by mechanical grinding, degreasing, pickling and alkaline etching to obtain a clean and activated metal surface. The specific treatment process is as follows: S1. The substrate surface was mechanically ground with 400#, 800#, 1000#, 1500# and 2000# silicon carbide sandpaper to make the surface flat and uniform; S2. The pretreated substrate was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface oil, and then rinsed with deionized water; S3. The cleaned substrate was immersed in dilute sulfuric acid solution for pickling to remove the natural oxide film, and then rinsed with deionized water; S4. The sample was then immersed in NaOH solution for alkaline etching to further activate the surface, and finally cleaned with deionized water and ethanol and dried.

[0055] (2) Constructing a rough interface through anodizing: The substrate treated in step (1) is placed in an electrolyte for anodizing treatment to form an anodized film with a porous structure on the substrate surface, thereby constructing a rough interface. The specific process includes the following steps: S1, using the substrate as the anode, a graphite plate as the cathode, and a mixture of sulfuric acid and aluminum sulfate as the electrolyte, wherein the concentration of sulfuric acid in the electrolyte is 165 g / L and the concentration of aluminum sulfate is 0.4 g / L; S2, controlling the anodizing current density to be 1.2 A / dm², the reaction temperature to be 20 ± 1 °C, and the oxidation time to be 40 min; S3, after the anodizing is completed, the sample is taken out, thoroughly rinsed with deionized water to remove residual electrolyte, and naturally dried under cold air conditions to obtain an anodized film with a porous structure on the surface.

[0056] (3) In-situ growth of CuAl-LDH: The anolyzed matrix is ​​immersed in CuAl-LDH. 2+ An alkaline reaction solution of the precursor is used to induce in-situ growth of CuAl layered double hydroxide (CuAl-LDH) in the pores and surface of the anodic oxide film via a hydrothermal reaction, resulting in an AO-CuAl-LDH composite film. The Cu / Al molar ratio in the CuAl layered double hydroxide is 2.0. The alkaline reaction solution is a mixture of 0.1 mol / L Cu(NO3)2·6H2O and 0.05 mol / L NaNO3, with the pH adjusted to 11.2 using a 2 mol / L NaOH solution. The hydrothermal reaction is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner at 150°C for 5 hours. After the reaction, the sample is allowed to cool naturally to room temperature, removed, thoroughly rinsed with deionized water, and dried in a vacuum drying oven at 80°C to obtain the AO-CuAl-LDH composite film.

[0057] (4) Introduction of cerium and construction of self-healing structure: During the growth of CuAl-LDH, cerium is introduced into Cu-containing structures... 2+ A 0.064 mol / L cerium nitrate (Ce(NO3)3·6H2O) solution was introduced into the alkaline reaction solution of the precursor, allowing cerium to enter the LDH interlayer and deposit on its surface to form cerium-based compounds, thereby preparing an AO-CuAl-LDH@Ce composite film with self-healing function.

[0058] (5) Superhydrophobic treatment: The obtained AO-CuAl-LDH@Ce composite film is modified with a low surface energy material using a hydrophobic agent to achieve superhydrophobic surface properties. The specific process includes the following steps: S1, prepare a hydrophobic agent by mixing hexadecyltrimethoxysilane, water and ethanol in a weight ratio of 3:1:16, and stir in a water bath at 40°C for 2 hours to ensure uniform mixing of each component; S2, immerse the AO-CuAl-LDH@Ce composite film obtained in step (4) in the hydrophobic agent at 40°C for 4 hours; S3, dry the hydrophobic treated AO-CuAl-LDH@Ce composite film in a vacuum drying oven at 60°C for 2 hours to obtain a superhydrophobic AO-CuAl-LDH@Ce composite film.

[0059] Example 3

[0060] A method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation includes the following steps:

[0061] (1) Substrate pretreatment: The 5083 aluminum alloy sheet was cut into a substrate with a size of Φ14mm×3mm. The substrate was pretreated by mechanical grinding, degreasing, pickling and alkaline etching to obtain a clean and activated metal surface. The specific treatment process is as follows: S1. The substrate surface was mechanically ground with 400#, 800#, 1000#, 1500# and 2000# silicon carbide sandpaper to make the surface flat and uniform; S2. The pretreated substrate was ultrasonically cleaned in acetone and anhydrous ethanol to remove surface oil, and then rinsed with deionized water; S3. The cleaned substrate was immersed in dilute sulfuric acid solution for pickling to remove the natural oxide film, and then rinsed with deionized water; S4. The sample was then immersed in NaOH solution for alkaline etching to further activate the surface, and finally cleaned with deionized water and ethanol and dried.

[0062] (2) Anodizing to construct a rough interface: The substrate treated in step (1) is placed in an electrolyte for anodizing treatment to form an anodized film with a porous structure on the surface of the substrate, thereby constructing a rough interface. The specific process includes the following steps: S1, using the substrate as the anode, the graphite plate as the cathode, and a mixture of sulfuric acid and aluminum sulfate as the electrolyte, wherein the concentration of sulfuric acid in the electrolyte is 160 g / L and the concentration of aluminum sulfate is 0.6 g / L; S2, controlling the anodizing current density to be 1.4 A / dm², the reaction temperature to be 20 ± 1℃, and the oxidation time to be 30 min; S3, after the anodizing is completed, the sample is taken out, thoroughly rinsed with deionized water to remove residual electrolyte, and naturally dried under cold air conditions to obtain an anodized film with a porous structure on the surface.

[0063] (3) In-situ growth of CuAl-LDH: The anolyzed matrix is ​​immersed in CuAl-LDH.2+ An alkaline reaction solution of the precursor is used to induce in-situ growth of CuAl layered double hydroxide (CuAl-LDH) in the pores and surface of the anolyl film via a hydrothermal reaction, resulting in an AO-CuAl-LDH composite film. The Cu / Al molar ratio in the CuAl layered double hydroxide is 3.0. The alkaline reaction solution is a mixture of 0.1 mol / L Cu(NO3)2·6H2O and 0.05 mol / L NaNO3, with the pH adjusted to 11.0 using a 2 mol / L NaOH solution. The hydrothermal reaction is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner at 160°C for 4 hours. After the reaction, the sample is allowed to cool naturally to room temperature, removed, thoroughly rinsed with deionized water, and dried in a vacuum drying oven at 80°C to obtain the AO-CuAl-LDH composite film.

[0064] (4) Introduction of cerium and construction of self-healing structure: During the growth of CuAl-LDH, cerium is introduced into Cu-containing structures... 2+ A 0.064 mol / L cerium nitrate (Ce(NO3)3·6H2O) solution was introduced into the alkaline reaction solution of the precursor, allowing cerium to enter the LDH interlayer and deposit on its surface to form cerium-based compounds, thereby preparing an AO-CuAl-LDH@Ce composite film with self-healing function.

[0065] (5) Superhydrophobic treatment: The obtained AO-CuAl-LDH@Ce composite film is modified with a low surface energy material using a hydrophobic agent to achieve superhydrophobic surface properties. The specific process includes the following steps: S1, prepare a hydrophobic agent by mixing hexadecyltrimethoxysilane, water and ethanol in a weight ratio of 3:1:16, and stir in a water bath at 45°C for 1.5h to ensure uniform mixing of each component; S2, immerse the AO-CuAl-LDH@Ce composite film obtained in step (4) in the hydrophobic agent at 45°C for 2h; S3, dry the hydrophobic treated AO-CuAl-LDH@Ce composite film in a vacuum drying oven at 70°C for 1.5h to obtain the superhydrophobic AO-CuAl-LDH@Ce composite film.

[0066] The polarization curve fitting corrosion parameters of AO-CuAl-LDH and AO-CuAl-LDH@Ce obtained in Examples 2 and 3 are shown in Table 5, and the EIS fitting parameters of the AO-CuAl-LDH@Ce coatings obtained in Examples 2 and 3 are shown in Table 6. The data in Tables 5 and 6 show that the AO-CuAl-LDH@Ce coating exhibits excellent corrosion resistance.

[0067] Table 5. Fitting corrosion parameters of polarization curves in Examples 2 and 3

[0068]

[0069] Table 6 EIS Fitting Parameters for Examples 2 and 3

[0070]

Claims

1. A method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation, characterized in that, The process includes the following steps: (1) Pretreatment of the substrate: The aluminum alloy substrate is pretreated by mechanical grinding, degreasing, pickling and alkaline etching to obtain a clean and activated metal surface; (2) Anodizing to build a rough interface: The substrate treated in step (1) is placed in an electrolyte for anodizing to form an anodized film with a porous structure on the substrate surface to build a rough interface; (3) In-situ growth of CuAl-LDH: The anodized substrate is immersed in a Cu-containing electrolyte. 2+ The alkaline reaction solution of the precursor is subjected to hydrothermal reaction to allow CuAl layered double hydroxide (CuAl-LDH) to grow in situ on the pores and surface of the anodic oxide film, thus obtaining an AO-CuAl-LDH composite film; (4) Introduction of cerium and construction of self-repairing structure: During the growth of CuAl-LDH, by introducing Cu-containing elements into the anodic oxide film, CuAl-LDH layered double hydroxide (CuAl-LDH) is grown in situ on the pores and surface of the anodic oxide film; (5) Introduction of cerium and construction of self-repairing structure: During the growth of CuAl-LDH, CuAl-LDH layered double hydroxide (CuAl-LDH) is grown in situ on the pores and surface of the anodic oxide film, thus obtaining an AO-CuAl-LDH composite film; 2+ Cerium salt is introduced into the alkaline reaction solution of the precursor, allowing cerium to enter the LDH interlayer and deposit on its surface to form cerium-based compounds, thereby preparing an AO-CuAl-LDH@Ce composite film with self-healing function.

2. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation as described in claim 1, characterized in that, It also includes step (5) hydrophobic modification treatment: using a hydrophobic agent to modify the obtained AO-CuAl-LDH@Ce composite film with low surface energy materials to achieve superhydrophobic surface properties.

3. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation according to claim 2, characterized in that, The hydrophobic agent in step (5) is a silane-based hydrophobic agent.

4. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation according to claim 3, characterized in that, The hydrophobic modification process in step (5) includes the following steps: S1, prepare a silane hydrophobic agent and stir it in a water bath at 40-60℃ for 1-2 hours to ensure that the components are mixed evenly; S2, immerse the AO-CuAl-LDH@Ce composite film obtained in step (4) in the hydrophobic agent at 40-50℃ for 2-4 hours; S3, dry the hydrophobic treated AO-CuAl-LDH@Ce composite film in a vacuum drying oven at 60-80℃ for 1-2 hours to obtain the superhydrophobic AO-CuAl-LDH@Ce composite film.

5. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation as described in claim 1, characterized in that, Step (2) of constructing a rough interface by anodizing includes the following steps: S1, using the substrate as the anode, the graphite plate as the cathode, and a mixture of sulfuric acid and aluminum sulfate as the electrolyte, wherein the concentration of sulfuric acid in the electrolyte is 160-170 g / L and the concentration of aluminum sulfate is 0.4-0.6 g / L; S2, controlling the anodizing current density to be 1.2-1.5 A / dm², the reaction temperature to be 20±1℃, and the oxidation time to be 20-40 min; S3, after the anodizing is completed, the sample is taken out, thoroughly rinsed with deionized water to remove residual electrolyte, and naturally dried under cold air conditions to obtain an anodized film with a porous structure on the surface.

6. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation according to claim 1, characterized in that, In the in-situ growth of CuAl-LDH in step (3), the alkaline reaction solution is a mixture of 0.1 mol / L Cu(NO3)2·6H2O and 0.05 mol / L NaNO3, and the pH of the mixture is adjusted to 10.8-11.2 using 2 mol / L NaOH solution.

7. The method for preparing a self-healing AO-CuAl-LDH@Ce composite film based on anodic oxidation according to claim 1, wherein the hydrothermal reaction in step (3) is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, and the hydrothermal reaction is carried out at 140-160℃ for 4-6 hours; after the reaction is completed, the sample is naturally cooled to room temperature, taken out, thoroughly rinsed with deionized water and dried to obtain the AO-CuAl-LDH composite film.

8. The method for preparing a self-healing AO-CuAl-LDH@Ce composite film based on anodic oxidation according to claim 1, wherein the Cu / Al molar ratio in the reaction system in step (3) is 1.5-3.

0.

9. The method for preparing a self-healing AO-CuAl-LDH@Ce composite thin film based on anodic oxidation as described in claim 1, characterized in that, The pretreatment of the substrate in step (1) includes the following processes: S1, mechanically polishing the surface of the substrate with silicon carbide sandpaper to make the surface smooth and uniform; S2, ultrasonically cleaning the polished substrate in acetone and anhydrous ethanol in sequence to remove surface oil stains, and then rinsing it with deionized water; S3, immersing the cleaned substrate in dilute sulfuric acid solution for acid washing to remove the natural oxide film, and then rinsing it with deionized water. S4. Immerse the substrate in NaOH solution for alkaline etching to further activate the surface. Finally, clean it with deionized water and ethanol in sequence and then dry it.

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