A method for preparing a metal-organic framework film layer with self-repairing performance by electrodeposition

Abstract

The application provides a method for preparing a metal organic framework film layer with self-repairing performance by an electrodeposition method, comprising the following steps: taking an aluminum alloy as an anode, taking an aluminum foil as a cathode, pressurizing and oxidizing in a tannic acid solution, forming an anodic oxidation film on the surface of the aluminum alloy, and obtaining an anodized aluminum alloy; adding N,N-dimethylformamide, a metal source and trimesic acid into the reacted tannic acid solution and uniformly mixing to obtain a film layer preparation liquid; taking the anodized aluminum alloy as a cathode and taking graphite as an anode, and performing electrodeposition in the film layer preparation liquid to form a self-repairing film layer on the aluminum alloy. The tannic acid is used as an acid solution of an anodic oxidation liquid, can prepare an anodic oxidation film on the surface of the metal, and can also be used as raw material for preparing a metal-MOF self-repairing film layer in the subsequent preparation; the use of waste acid is reduced, and the preparation process is simplified; the electrochemical performance and corrosion resistance of the film layer are improved, and the film layer has good self-repairing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion-resistant intelligent film layers of metal materials, and in particular to a method for preparing a metal organic framework corrosion-resistant self-repairing film layer containing the polyphenol compound tannic acid on the surface of an aluminum alloy. Background Art

[0002] Aluminum alloys, with their low density, high strength, and ease of processing, are widely used in transportation, machinery, and construction. Many machines and equipment operate in tidal marine environments. Although aluminum alloys form a dense oxide film in air, exposure to corrosive media can lead to uneven oxide films, resulting in galvanic corrosion, pitting, and stress corrosion cracking. These conditions can shorten the metal's service life and even damage devices, posing safety risks. To address these issues, researchers have employed a variety of treatment techniques. Among them, metal-organic framework (MOF) films can slow the reaction between the cathode and anode, increasing the ingress pathway for corrosive media and thereby blocking the metal's corrosion process. Polyphenol compounds, upon contact with metals, form a film on the metal surface that is a metal complex with corrosion resistance. Encapsulating the polyphenol compounds in a MOF with adjustable pore size enables a combined active and passive corrosion protection scheme, releasing corrosion inhibitors to provide secondary protection even after the film is destroyed.

[0003] There are currently many methods for preparing MOF film-coated corrosion inhibitors, but most methods require the preparation of MOF-coated corrosion inhibitor powder first, then adding it to a certain coating, and finally applying it to the metal surface by coating. This method is time-consuming and labor-intensive, and is prone to problems such as poor bonding strength. In patent CN116815268A, an aluminum alloy is first anodized using a mixed solution of phosphoric acid and oxalic acid as an electrolyte for anodization, and then an MOF film is further prepared on the aluminum alloy surface by electrodeposition, which can reduce the reaction time to a certain extent and improve the bonding strength. However, in its preparation process, the remaining mixed solution after the anodization is completed becomes waste liquid, and in the subsequent preparation of MOF, an electrolyte solution needs to be prepared separately, which makes the process complicated and easily generates unnecessary pollution sources. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a metal-MOF organic framework film layer with self-repairing properties. The self-repairing corrosion-resistant film layer of the MOF-coated corrosion inhibitor is directly prepared on the metal surface by the electroplating method, which has the advantages of simple process, short time and good bonding strength. The polyphenol compound tannic acid is directly prepared into an anodic oxidation electrolyte for preparing an anodic oxide layer; at the same time, the solution can still be used as part of the solution in the subsequent steps, and continue to participate in the experiment after the anodization is completed to provide a corrosion inhibitor, and then prepare the MOF film layer by electroplating. It not only provides an electrolyte for anodization, but also provides a corrosion inhibitor for subsequent steps, reduces the discharge of acid waste liquid, and is more environmentally friendly. In addition, in the subsequent step of preparing MOF, the solution and the required corrosion inhibitor are mixed in one step, thereby simplifying the operation process. At the same time, the prepared MOF-coated corrosion inhibitor film layer also has the function of corrosion resistance and self-repair, further improving the corrosion resistance of the aluminum alloy surface. The purpose of the present invention is achieved through the following technical solutions:

[0005] The present invention provides a method for preparing a metal organic framework film layer with self-repairing properties by electrodeposition, which specifically comprises the following steps:

[0006] S1. Using an aluminum alloy as an anode and an aluminum foil as a cathode, oxidizing under pressure in a tannic acid solution to form an anodic oxide film on the surface of the aluminum alloy to obtain an anodic oxide aluminum alloy;

[0007] S2. Add N,N-dimethylformamide, a metal source, and trimesic acid to the reacted tannic acid solution and mix them evenly to obtain a film preparation solution;

[0008] S3. Using anodized aluminum alloy as cathode and graphite as anode, electrodeposition is performed in the film preparation solution to form a self-repairing film on the aluminum alloy.

[0009] As some specific embodiments of the present invention, in step S1, the aluminum alloy is first subjected to grinding, degreasing and drying treatments in sequence before anodizing.

[0010] As some specific embodiments of the present invention, the degreasing liquid used in the degreasing treatment is a mixed solution of sodium silicate nonahydrate and sodium phosphate dodecahydrate.

[0011] Furthermore, in the degreasing liquid, the concentration of sodium silicate nonahydrate is 0.005-0.015 g / mL;

[0012] And / or, the concentration of the sodium phosphate dodecahydrate is 0.02-0.06 g / mL.

[0013] As some specific embodiments of the present invention, the oil removal treatment time is 1 to 3 minutes;

[0014] And / or, the temperature of the degreasing treatment is 70-80°C.

[0015] Preferably, the degreasing treatment time is 2 min;

[0016] And / or, the temperature of the degreasing treatment is 80°C.

[0017] As some specific embodiments of the present invention, after the degreasing treatment, the aluminum alloy is ultrasonically cleaned in ethanol and distilled water.

[0018] As some specific embodiments of the present invention, in step S1, the concentration of the tannic acid solution is 0.01-0.03 g / mL.

[0019] Preferably, in step S1, the concentration of the tannic acid solution is 0.01 g / mL. The present invention also optimizes the concentration of tannic acid as an anodic oxidation solution, as different concentrations can affect the film-forming effect of the anodic oxide film on the metal surface, thereby affecting the subsequent electrodeposition preparation of the MOF film. The optimal concentration of tannic acid after optimization is 10 g / L, i.e., 0.01 g / mL.

[0020] As some specific embodiments of the present invention, in step S1, the voltage of the pressurized oxidation is 10-20 V;

[0021] And / or, the pressurized oxidation time is 0.5 to 1.5 h.

[0022] As some specific embodiments of the present invention, in step S1, after obtaining the anodized aluminum alloy, it is cleaned and then dried.

[0023] As some specific embodiments of the present invention, in step S2, when preparing the film preparation solution, the volume ratio of N,N-dimethylformamide to tannic acid solution added is 3:2~2:3;

[0024] And / or, in the film preparation solution, the concentration of trimesic acid is 0.015-0.035 g / mL.

[0025] As some specific embodiments of the present invention, in step S2, the metal source is at least one of cerium nitrate hexahydrate, cobalt nitrate hexahydrate, and nickel nitrate hexahydrate.

[0026] As some specific embodiments of the present invention, in step S2, the concentration of the metal source is 0.03-0.07 g / mL.

[0027] Preferably, the metal source is cerium nitrate hexahydrate, and the concentration of the cerium nitrate hexahydrate is 0.03-0.07 g / mL.

[0028] As some specific embodiments of the present invention, the self-healing film layer is metal-MOF@TA, specifically at least one of Ce-MOF@TA, Co-MOF@TA, and Ni-MOF@TA.

[0029] As some specific embodiments of the present invention, in step S3, the voltage of electrodeposition is 8 to 20 V;

[0030] and / or, the electrodeposition temperature is 20-30°C;

[0031] And / or, the electrodeposition time is 20 to 60 min.

[0032] Preferably, in step S3, the voltage of electrodeposition is 15 V;

[0033] and / or, the electrodeposition temperature is 25°C;

[0034] And / or, the electrodeposition time is 40 min.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention uses tannic acid, a polyphenol weak acid corrosion inhibitor, as the acid solution of the anodic oxidation solution. While preparing an anodic oxidation film on the metal surface, it can also continue to serve as a raw material for the subsequent preparation of a metal-MOF self-repairing film layer. This reduces the use of waste acid and simplifies the preparation process.

[0037] (2) The anodizing and electrodeposition steps of the present invention use low voltage and short time, which is more energy-saving and environmentally friendly;

[0038] (3) When preparing the membrane preparation liquid, the present invention adopts a method of adding and dissolving the raw materials in one step, which simplifies the preparation steps, and the prepared self-repairing membrane has excellent self-repairing properties;

[0039] (4) The electrochemical test of the self-repairing film showed that its corrosion current density could reach 3.65×10 -9 A.cm -2 The anti-corrosion efficiency of aluminum alloy reaches 99.97%, and the AC impedance value reaches 4.83×10 7 Ω·cm 2 , the electrochemical performance of the self-repairing film prepared by the present invention is better;

[0040] (5) The self-repairing film layer was immersed in 3.5 wt.% sodium chloride salt water and 5 wt.% sodium chloride neutral salt spray test. After immersion in salt water for 14 days, the film layer was still intact and had good corrosion resistance. In the neutral salt spray test, no obvious changes were found on the surface of the film layer after 80 days of salt spray, which showed good corrosion resistance and salt spray resistance.

[0041] (6) The EDS carbon and oxygen element spectrum analysis of the scratches on the self-repairing film layer before and after salt spray was carried out. After the salt spray test, the content of C and O elements in the scratched part increased significantly compared with that before salt spray. The corrosion inhibitor tannic acid was released on the surface of the aluminum alloy and actively combined with aluminum ions to form an anti-corrosion metal complex, forming a layer of corrosion inhibition film, which provided secondary protection for the aluminum alloy and repaired the aluminum alloy surface at the scratch, preventing the corrosive medium from contacting the substrate, thereby achieving the purpose of continuing to protect the metal surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0043] Figure 1 SEM images of the aluminum alloy, anodic oxide film, and Ce-MOF@TA film layer in Example 1; wherein, a is an SEM image of the aluminum alloy, b is an SEM image of the porous oxide film (anodic oxide film) on the surface of the aluminum alloy, and c is an SEM image of the self-healing film layer Ce-MOF@TA formed on the surface of the aluminum alloy;

[0044] Figure 2 The electrochemical test results of the aluminum alloy, anodic oxide film, and Ce-MOF@TA film in Example 1 are shown, where a is the potentiodynamic polarization curve and b is the electrochemical impedance spectroscopy.

[0045] Figure 3 This is the electrochemical impedance modulus test spectrum of the aluminum alloy surface after the Ce-MOF@TA film layer is attached to the aluminum alloy surface in Example 1 and then immersed in a 5 wt.% NaCl solution for 0-14 days;

[0046] Figure 4 This is a graph showing the results of a 0-80 day salt spray test after the film layer is attached to the aluminum alloy surface in Example 1;

[0047] Figure 5 EDS carbon and oxygen element spectra of the scratches before and after salt spray. a, b are the C and O elements of the scratches of Ce-MOF@TA before salt spray; c, d are the C and O elements of the scratches of Ce-MOP@TA after salt spray. DETAILED DESCRIPTION

[0048] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0049] Example 1

[0050] A method for preparing a corrosion-resistant Ce-MOF@TA self-repairing film coated with tannic acid is provided. The specific steps are as follows:

[0051] (1) Aluminum alloy pretreatment

[0052] A 15 × 15 × 3 mm aluminum alloy 6061 substrate was polished using 180#, 600#, and 1000# sandpaper. A 50 mL aqueous solution of 0.5 g sodium silicate nonahydrate and 2 g sodium phosphate dodecahydrate was used as a degreasing solution. The polished aluminum alloy sheet was placed in the degreasing solution and degreased at 80°C for 2 minutes. The sheet was then ultrasonically cleaned with ethanol and then distilled water for 10 minutes each, then removed and dried for later use.

[0053] (2) Preparation of anodic oxide film:

[0054] Weigh 0.4 g of tannic acid to prepare 20 mL of anodizing solution;

[0055] The pretreated aluminum sheet was used as the anode and the aluminum foil was used as the cathode. A DC power supply was used to react in the anodizing solution at 15V at room temperature for 1 hour. The aluminum sheet was taken out and rinsed with deionized water. The aluminum sheet was then dried in an oven to obtain an anodized film.

[0056] (3) Preparation of Ce-MOF@TA film:

[0057] 20 mL of N,N-dimethylformamide was added to the anodizing solution, 2 g of cerium nitrate hexahydrate and 1 g of trimesic acid were added to the solution, and the solution was dissolved by ultrasonic stirring to obtain the film preparation solution.

[0058] Connect the aluminum alloy containing the anodic oxide film to the cathode of a DC power supply, and the graphite to the anode of a DC power supply. Place the aluminum alloy in the film preparation solution to form a current path. Set the deposition voltage to 15 V and perform constant-voltage deposition at 25°C for 40 minutes. After deposition, rinse with distilled water and dry in a 50°C oven.

[0059] The tannic acid, sodium silicate nonahydrate, sodium phosphate dodecahydrate, cerium nitrate hexahydrate, trimesic acid and N,N-dimethylformamide are all of chemical purity or above.

[0060] The self-repairing film obtained in Example 1 was subjected to various performance verifications, as follows:

[0061] 1. SEM morphology characterization

[0062] The aluminum alloy in Example 1, the anodic (porous) oxide film formed on the surface of the aluminum alloy, and the Ce-MOF@TA self-repairing film formed on the surface of the aluminum alloy were characterized by SEM images.Figure 1 As shown. Among them, a is the SEM image of aluminum alloy, b is the SEM image of the porous oxide film on the surface of aluminum alloy, and c is the SEM image of Ce-MOF@TA. Figure 1 It can be seen that the Ce-MOF@TA self-healing film layer was successfully synthesized, has good bonding with the aluminum alloy substrate, and is evenly distributed on the aluminum alloy surface.

[0063] 2. Corrosion resistance test and electrochemical impedance test

[0064] The corrosion resistance of the Ce-MOF@TA self-healing film prepared in Example 1 was tested using a CHI760 electrochemical workstation in a three-electrode system (calomel electrode as reference electrode, platinum electrode as auxiliary electrode, aluminum alloy / aluminum alloy with an anodic oxide film on the surface / aluminum alloy with a Ce-MOF@TA self-healing film on the surface as working electrode, and 3.5 wt.% sodium chloride solution as electrolyte). The potentiodynamic polarization curve was used to study the corrosion resistance of the aluminum alloy surface film. After the open circuit potential was stabilized, the test was performed at a scan rate of 10 mV / s. The frequency range of the impedance test was 10 5 Hz to 10 -2 Hz, a 10 mV sinusoidal signal perturbation was swept through the open circuit potential. The measured potentiodynamic polarization curve and electrochemical impedance spectrum are shown in Figure 2 shown.

[0065] according to Figure 2 The potentiodynamic polarization curve in a shows that the corrosion potential of the Ce-MOF@TA film on the aluminum alloy surface prepared in Example 1 is -0.553 V, and the corrosion current density is 3.65×10 -9 A.cm -2 The corrosion potential of the anodic oxide film is -0.698 V, and the corrosion current density is 9.42×10 -7 A.cm -2 The corrosion potential of 6061 aluminum alloy substrate is -0.699 V, and the corrosion current density is 1.24×10 -5 A.cm -2 It can be seen that the corrosion potential of the Ce-MOF@TA film layer has shifted positively, and the corrosion current density is reduced by 4 and 2 orders of magnitude compared with the anodic oxide film and aluminum alloy substrate, respectively.

[0066] according to Figure 2 b is the electrochemical impedance spectrum. It can be seen that after the Ce-MOF@TA film is prepared on the aluminum alloy surface, the impedance fitting results show that the R ct The value is 2.58×10 3 Ω·cm 2 Increased to 4.83×10 7 Ω·cm2 , significantly improving the corrosion resistance of aluminum alloy, and the anti-corrosion efficiency of aluminum alloy can reach 99.97%.

[0067] The corrosion current density of the Ce-MOF@LS film prepared in patent CN116815268A is 1.045×10 -8 A.cm -2 , AC impedance value 3.0×10 6 Ω·cm 2 In comparison, the self-repairing film layer prepared by the present invention has lower corrosion current density, higher AC impedance value, better electrochemical performance, and stronger corrosion resistance.

[0068] 3. Immersion test and intermittent salt spray test

[0069] The working environment includes immersion test and intermittent salt spray test.

[0070] (1) Immersion test: The Ce-MOF@TA film prepared in Example 1 was immersed in a 3.5 wt.% NaCl solution. The impedance test was performed on the film at 0, 2, 7, and 14 days. The changes in the corrosion resistance of the film were analyzed by the modulus diagram. The results are as follows: Figure 3 shown.

[0071] From the modulus diagram of the immersion experiment ( Figure 3 ) analysis: Ce-MOF@TA membrane layer was immersed in salt solution, and its |Z| 0.01 The Hz value has increased from 1.0×10 7 Ω·cm 2 Gradually reduced to 1.8×10 5 Ω·cm 2 On the fourteenth day, it rose slightly, decreasing by two orders of magnitude compared to the initial level, but still maintaining a 5-fold increase, thus providing relatively long-lasting protection for the substrate. Even after fourteen days of immersion, the Ce-MOF@TA film still maintained good corrosion resistance.

[0072] (2) Salt spray test:

[0073] The test was conducted with a 12-hour spray (5 wt.% NaCl solution) and a 12-hour rest period. After the rest period, photos were collected and analyzed. The results are as follows: Figure 4 shown.

[0074] From the salt spray results ( Figure 4) , the Ce-MOF@TA film showed no obvious corrosion spots after 80 days. Pitting on the scratched Ce-MOF@TA film appeared after approximately 20 days, with no subsequent corrosion spots appearing elsewhere. This demonstrates that the Ce-MOF@TA film provides extended protection for the aluminum alloy substrate in a salt spray environment. After blocking the intrusion of the corrosive medium, the film is damaged. The tannic acid in the film then actively combines with aluminum ions to form an anti-corrosion metal complex, forming a secondary protective film that repairs the scratched aluminum alloy surface. In summary, the addition of the corrosion inhibitor TA improves the film's durability.

[0075] (3) Perform EDS image test on the scratches on the film before and after the salt spray test (such as Figure 5 As shown), the C and O elements are intercepted, Figure 5 a and b are the C and O elements at the scratch of Ce-MOF@TA before salt spray, Figure 5 Figures c and d show the C and O elements in the scratched area of ​​Ce-MOF@TA after salt spray testing, respectively. The C and O elements in the scratched area significantly increased after the salt spray test compared to before the test. This indicates that the corrosion inhibitor was successfully released on the aluminum alloy surface, actively forming a corrosion-inhibiting film on the metal substrate, preventing the corrosive medium from contacting the substrate and thus continuing to protect the metal surface.

[0076] Example 2

[0077] A method for preparing a corrosion-resistant Ni-MOF@TA self-healing film coated with tannic acid is provided. The other steps for preparing the self-healing film are the same as those in Example 1, except that in step (3), cerium nitrate hexahydrate is replaced with nickel nitrate hexahydrate. The amount of nickel nitrate hexahydrate added is 1.5 g. The nickel nitrate hexahydrate is of chemical purity or higher.

[0078] After the Ni-MOF@TA film was prepared on the aluminum alloy surface, its corrosion current density was measured to be 1.48×10 -7 A.cm -2 The Ni-MOF@TA film prepared in Example 2 also has good self-healing properties. After the Ni-MOF on the metal surface is destroyed, the released TA will be adsorbed onto the aluminum alloy and coordinate with the aluminum ions through the metal heteroatom / π electron interaction to form a self-assembled corrosion-resistant film, thereby automatically repairing the original corrosion-resistant film defects on the aluminum alloy surface.

[0079] Example 3

[0080] A method for preparing a corrosion-resistant Co-MOF@TA self-healing film coated with tannic acid is provided. The other steps for preparing the self-healing film are the same as those in Example 1, except that in step (3), cerium nitrate hexahydrate is replaced with cobalt nitrate hexahydrate, and the amount of cobalt nitrate hexahydrate added is 1.5 g. The cobalt nitrate hexahydrate is of chemical purity or higher.

[0081] After the Co-MOF@TA film was prepared on the aluminum alloy surface, the corrosion current density was 1.45×10 -7 A.cm -2 The Co-MOF@TA film prepared in Example 3 also has good self-healing properties. After the Co-MOF on the aluminum alloy surface is destroyed, the released TA molecules coordinate with the aluminum ions through the metal heteroatom / π electron interaction to form a self-assembled corrosion-resistant film, thereby automatically repairing the original corrosion-resistant film defects on the aluminum alloy surface.

[0082] In addition to the metal sources cerium nitrate hexahydrate, nickel nitrate hexahydrate and cobalt nitrate hexahydrate used in Examples 1-3, the present invention also uses other metal sources for verification. The results show that when the cerium element in cerium nitrate hexahydrate is replaced by other elements such as Mn and Zn, it is impossible to further form a self-repairing film layer on the surface of the aluminum alloy after the anodized film is synthesized. Only Ce, Ni and Co elements can form a self-repairing film layer on the surface of the aluminum alloy.

[0083] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a metal organic framework film layer with self-repairing properties by electrodeposition, characterized in that: The steps include: S1. Using an aluminum alloy as an anode and an aluminum foil as a cathode, oxidizing under pressure in a tannic acid solution to form an anodic oxide film on the surface of the aluminum alloy to obtain an anodic oxide aluminum alloy; S2. Add N,N-dimethylformamide, a metal source, and trimesic acid to the reacted tannic acid solution and mix them evenly to obtain a film preparation solution; S3, using anodized aluminum alloy as a cathode and graphite as an anode, performing electrodeposition in a film preparation solution to form a self-repairing film on the aluminum alloy; In step S1, the concentration of the tannic acid solution is 0.01-0.03 g / mL, and the voltage of the pressurized oxidation is 10-20 V; in step S2, the metal source is at least one of cerium nitrate hexahydrate, cobalt nitrate hexahydrate, and nickel nitrate hexahydrate, the volume ratio of N,N-dimethylformamide to tannic acid solution is 3:2-2:3, and the concentration of trimesic acid is 0.015-0.035 g / mL.

2. The method according to claim 1, characterized in that In step S1, the pressure oxidation time is 0.5 to 1.5 hours.

3. The method according to claim 1, characterized in that In step S2, the concentration of the metal source in the film preparation solution is 0.03-0.07 g / mL.

4. The method according to claim 1, wherein In step S3, the voltage of electrodeposition is 8 to 20 V; and / or, the electrodeposition temperature is 20-30°C; And / or, the electrodeposition time is 20 to 60 min.

5. The method according to claim 1, wherein In step S1, the aluminum alloy is first subjected to grinding, degreasing and drying treatments before anodizing.

6. The method according to claim 5, characterized in that The degreasing liquid used in the degreasing treatment is a mixed solution of sodium silicate nonahydrate and sodium phosphate dodecahydrate.

7. The method according to claim 6, characterized in that In the degreasing liquid, the concentration of sodium silicate nonahydrate is 0.005-0.015 g / mL; And / or, the concentration of the sodium phosphate dodecahydrate is 0.02-0.06 g / mL.

8. The method according to claim 7, characterized in that The degreasing treatment time is 1 to 3 minutes; And / or, the temperature of the degreasing treatment is 70-80°C.

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