An anti-corrosion and wear-resistant coating with pH response and its preparation method

Abstract

The present invention belongs to the technical field of functional coatings, and specifically discloses a pH-responsive anti-corrosion and wear-resistant coating and a preparation method thereof. The anti-corrosion and wear-resistant coating is composed of composite nanocontainers and polymer resins, and the composite nanocontainers are composed of two-dimensional MXene nanosheets and zeolitic imidazolate frameworks. Among them, the mass ratio of the composite nanocontainers to the polymer resins is 1:200 to 1:30; the mass ratio of the zeolitic imidazolate frameworks to the two-dimensional MXene nanosheets is 1:2 to 1:10; the two-dimensional MXene nanosheets are selected from one or more of Ti3C2T x , V2CT x , Nb2CT x ; the zeolitic imidazolate frameworks include one or more of ZIF-7, ZIF-8, and ZIF-62; the polymer resins are one or more of polyurethane resins, silicone resins, epoxy resins, and fluorocarbon resins. The present invention also discloses a specific preparation method of the above coating, and the prepared coating can respond to the corrosion at the interface between the coating and the metal, showing great potential in intelligent protection applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional coatings, and particularly relates to an anti-corrosion and wear-resistant coating with pH responsiveness and a preparation method thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] During the severe marine service of polymer coatings, microcracks and micropores will inevitably occur, thereby causing local corrosion. Moreover, the continuous scouring of seawater will lead to the peeling failure of the coating, economic losses and even safety accidents. Therefore, it is very necessary to develop a composite coating with local corrosion response and coordinated anti-corrosion and wear resistance.

[0004] In view of the above situation, various corrosion inhibitors have been developed for the corrosion protection of metals or alloys. It is reported that inhibitors can affect the kinetics of electrochemical reactions during the corrosion process, thereby slowing down the dissolution of metals. Existing inhibitors (corrosion inhibitors) can be divided into two categories: organic corrosion inhibitors and inorganic corrosion inhibitors. However, it has been proved that traditional inorganic corrosion inhibitors (such as chromates, nitrates, metal oxides) usually show environmental toxicity, while most organic corrosion inhibitors are low in efficiency and high in price. Therefore, new corrosion inhibitors and a new generation of organic-inorganic composite corrosion inhibitors have attracted much attention in recent years. At present, technicians urgently need to develop a new strategy to construct an anti-corrosion and wear-resistant coating with local corrosion response to achieve high environmental adaptability for long-term anti-corrosion applications.

[0005] The self-assembled structure characteristics of metal-organic framework compounds (MOFs) generated by selecting appropriate metals and organic ligands endow the material with ideal structures and functions. Therefore, MOFs with corrosion inhibition ability have become a frontier topic. When erosive substances penetrate into the MOF structure, the corrosion inhibition process begins, resulting in the detachment of metal ions and organic ligands, and further releasing inhibitors to achieve corrosion protection. Among them, zeolitic imidazolate framework materials (ZIFs) are a typical type of MOFs, which have pH responsiveness and good compatibility with polymers, and show great potential in intelligent protection applications. Summary of the Invention

[0006] In response to the needs of the prior art, the purpose of the present invention is to provide an anti-corrosion and wear-resistant coating with pH responsiveness and a preparation method thereof, so as to expand the application of polymer coatings in the deep sea.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] In the first aspect of the present invention, a pH-responsive anti-corrosion and wear-resistant coating is provided. The pH-responsive anti-corrosion and wear-resistant coating is composed of composite nanocontainers and a polymer resin. The composite nanocontainers are composed of two-dimensional MXene nanosheets and zeolitic imidazolate frameworks;

[0009] Among them, the mass ratio of the composite nanocontainers to the polymer resin is 1:200 to 1:30;

[0010] In the composite nanocontainers, the mass ratio of the zeolitic imidazolate framework to the two-dimensional MXene nanosheets is 1:2 to 1:10.

[0011] The two-dimensional MXene nanosheets are selected from one or more of Ti3C2T x 、V2CT x 、Nb2CT x ;

[0012] The zeolitic imidazolate frameworks are selected from one or more of ZIF-7, ZIF-8, and ZIF-62;

[0013] The polymer resin is selected from one or more of polyurethane resin, silicone resin, epoxy resin, and fluorocarbon resin.

[0014] In the second aspect of the present invention, a preparation method of the above-mentioned pH-responsive anti-corrosion and wear-resistant coating is provided, including the following steps:

[0015] S1. Adding MAX powder to an etching solution for an etching reaction to obtain MXene nanosheets;

[0016] S2. Modifying the MXene nanosheets with zeolitic imidazolate frameworks to obtain composite nanocontainers;

[0017] S3. Mixing the composite nanocontainers with the polymer resin to form a composite coating.

[0018] Preferably, in step S1, the MAX powder is selected from one or more of Ti3AlC2, V2AlC, and Nb2AlC; the etching solution is selected from one or more of HF, HCl, and LiF.

[0019] Preferably, in step S1, the etching reaction time is 12 to 36 h; more preferably, the etching reaction time is 24 h; the mixture obtained after the etching reaction needs to be washed with deionized water, centrifuged, filtered, and freeze-dried in sequence;

[0020] Among them, the rotation speed of the centrifugation is set to 3300 to 3700 rpm; preferably, the rotation speed is set to 3500 rpm;

[0021] The pH value of the supernatant after centrifugation is not lower than 6;

[0022] The filtration is carried out by vacuum-assisted filtration using a polyvinylidene fluoride (PVDF) membrane with a pore size of 0.22 μm, and then the MXene deposit is washed again with deionized water;

[0023] The time for freeze-drying is 20 - 26 h; preferably, the time for freeze-drying is 24 h.

[0024] Preferably, in step S2, the zeolitic imidazolate framework is obtained by separately dissolving Zn(NO3)2·6H2O and benzimidazole, followed by mixing reaction, and then centrifugation, washing, and drying in sequence;

[0025] Among them, the molar ratio of Zn(NO3)2·6H2O to benzimidazole is 1:7;

[0026] Zn(NO3)2·6H2O is dissolved in DMF, and benzimidazole is dissolved in absolute methanol;

[0027] The time for the mixing reaction is 12 - 36 h; preferably, the time for the mixing reaction is 24 h;

[0028] The washing is carried out 2 - 4 times with an organic solvent; preferably, the organic solvent is methanol;

[0029] The temperature for drying is 35 - 45 °C, and the time is 20 - 26 h; preferably, the temperature for drying is 40 °C, and the time is 24 h.

[0030] Preferably, in step S2, the composite nanocontainer is obtained by separately dissolving MXene nanosheets and the zeolitic imidazolate framework in ethanol, followed by mixing reaction, and then centrifugation and drying in sequence;

[0031] Among them, the mass ratio of the MXene nanosheets to the zeolitic imidazolate framework is 1:1 - 3:1; preferably, the mass ratio of the MXene nanosheets to the zeolitic imidazolate framework is 2:1;

[0032] The time for the mixing reaction is 20 - 26 h; preferably, the time for the mixing reaction is 24 h;

[0033] The temperature for drying is 35 - 45 °C, and the time is 8 - 15 h; preferably, the temperature for drying is 40 °C, and the time is 12 h.

[0034] Preferably, in step S3, the composite coating is obtained by reacting an alcohol suspension of the composite nanocontainer, an aqueous curing agent, and a polymer resin, and then performing degassing treatment, coating on the electrode, and electrode curing in sequence;

[0035] Among them, the mass ratio of the waterborne curing agent to the polymer resin in the composite nanocontainer is 3:1 to 1:1; preferably, the mass ratio of the waterborne curing agent to the polymer resin in the composite nanocontainer is 3:2;

[0036] The alcohol suspension is preferably an ethanol suspension; the concentration of the ethanol suspension is 8 - 12 mg / mL; preferably, the concentration of the ethanol suspension is 10 mg / mL;

[0037] The time of the degassing treatment is 5 - 15 min; preferably, the time of the degassing treatment is 10 min;

[0038] The waterborne curing agent is selected from one or more of polyetheramine D230, polyetheramine D400, and polyetheramine D2000;

[0039] The specific operation of the coating is as follows: Use a wire bar coater to coat the composite coating on the surface of the pretreated carbon steel electrode, with a thickness of 80 ± 5 μm;

[0040] Preferably, the specific operation of the curing is to first cure the coated electrode at 25 - 30 °C for 8 - 12 h, and then raise the temperature to 40 - 80 °C for 8 - 12 h; more preferably, the coated electrode is first cured at 25 °C for 12 h, and then raised the temperature to 60 °C for 12 h.

[0041] In the third aspect of the present invention, there is provided an application of the above-mentioned anti-corrosion and wear-resistant coating with pH response in the deep sea.

[0042] The beneficial effects obtained by one or more of the above technical solutions of the present invention are as follows:

[0043] (1) In the present invention, MXene is first used as a substrate and ZIF-7 is used as a modifying particle to synthesize a two-dimensional composite nanocontainer, and then it is embedded in a polymer coating through a simple preparation method. In the initial stage of service, the two-dimensional composite nanocontainer can effectively extend the penetration path of the corrosive medium and exhibit excellent passive physical barrier effect;

[0044] When local corrosion appears in the early stage, due to its stimulus-responsive characteristics, the local acidification in the anodic region causes the decomposition of the two-dimensional composite nanocontainer, resulting in the rapid release of a large amount of benzimidazole (BIM), thereby effectively inhibiting the corrosion propagation at the coating / metal interface.

[0045] (2) The present invention relates to the versatility of embedding two-dimensional composite nanocontainers in coatings, and the designed intelligent system can be used to construct a new generation of intelligent protective materials for service in extremely harsh environments. Description of the Drawings

[0046] The accompanying drawings of the specification, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0047] Figure 1 Scanning electron microscope images of ZIF-7 nanoparticles and ZIF-7-loaded two-dimensional composite nanocontainers in Example 1 of the present invention (where, a1 are ZIF-7 nanoparticles; a2 is an enlarged view of ZIF-7 nanoparticles; b1 is a two-dimensional composite nanocontainer loaded with ZIF-7; b2 is an enlarged view of the two-dimensional composite nanocontainer loaded with ZIF-7);

[0048] Figure 2 Solubility photos and adsorption kinetic curves of ZIF-7 in solutions with different pH values in Example 1 of the present invention;

[0049] Figure 3 Impedance diagrams, phase angle diagrams, and Nyquist diagrams of carbon steel after immersion in 3.5 wt% NaCl solution with and without nanocontainers (500 mg / L) for different times;

[0050] Figure 4 Schematic diagram of the synergistic protection mechanism of the pH-responsive anti-corrosion and wear-resistant coating in Examples 1 to 3 of the present invention. Detailed Description of the Invention

[0051] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0052] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0053] Example 1 : This example provides a preparation method of a pH-responsive anti-corrosion and wear-resistant coating.

[0054] S1. Slowly add 1.5 g of Ti3C2T X powder to 30 mL of an etching solution mixed with HCl and LiF, and magnetically stir at room temperature for 5 - 30 min. Then react at room temperature for 24 h. Wash the mixture with deionized water and centrifuge several times at 3500 rpm until the pH value of the supernatant is not less than 6. Then perform vacuum-assisted filtration with a polyvinylidene fluoride (PVDF) membrane with a pore size of 0.22 μm, and re-wash the MXene sediment with deionized water. Finally, freeze-dry the sediment under vacuum for 24 h to obtain pure Ti3C2T XMXene nanosheets;

[0055] S2. Dissolve 3.2 g of Zn(NO3)2·6H2O in 100 mL of DMF, and dissolve 9 g of benzimidazole in 100 mL of anhydrous methanol. After ultrasonic dissolution, gradually mix the two and stir for 24 h at 25 °C using a constant-temperature heating magnetic stirrer. Then, centrifuge at 8000 rpm and remove the supernatant. Wash the final product with methanol, and then repeat centrifugation three times with a high-speed centrifuge, and wash with methanol each time. Dry the final product in a vacuum oven at 40 °C for 24 h to obtain pure white ZIF-7 powder;

[0056] S3. Take 0.5 g of Ti3C2T X MXene nanosheets and 0.25 g of ZIF-7 nanoparticles are respectively dissolved in 50 mL of ethanol, ultrasonically dissolved, and then mixed and stirred for 24 h. Centrifuge at a speed of 3000 rpm for 2 min, and place the final product in a vacuum drying oven (40 °C) for 12 h to obtain Mxene@ZIF-7 two-dimensional composite nanocontainers;

[0057] S4. Mix 5 mL of the ethanol suspension (10 mg / mL) of Mxene@ZIF-7 two-dimensional composite nanocontainers with an aqueous curing agent mixed with 3 g of polyetheramine D400 and polyetheramine D2000. Ultrasonically treat the mixture for 5 min and then stir with a glass rod for 10 min. Then add 2 g of EP resin (E-51), and then stir for 20 min. To ensure the density of the coating, degas the mixture in a vacuum oven at room temperature for 10 min. Finally, use a wire bar coater to coat the composite coating on the surface of a pretreated carbon steel electrode with a thickness of 80 ± 5 μm. Cure the coated electrode at room temperature for 12 h, and then place it in an oven at 60 °C for 12 h, and name it MXene@ZIF-7 / EP coating.

[0058] Example 2 : This example provides a preparation method of an anti-corrosion and wear-resistant coating with pH response.

[0059] S1. Slowly add 1.5 g of Ti3C2T X powder to an etching solution mixed with 30 mL of HCl and LiF, and magnetically stir at room temperature for 5 - 30 min. Then react at room temperature for 24 h. Wash the mixture with deionized water and centrifuge several times at 3500 rpm until the pH value of the supernatant is not less than 6. Then perform vacuum-assisted filtration with a polyvinylidene fluoride (PVDF) membrane with a pore size of 0.22 μm, and re-wash the MXene sediment with deionized water. Finally, freeze-dry the sediment in a vacuum for 24 h to obtain pure Ti3C2T X MXene nanosheets;

[0060] S2. Dissolve 3.2 g of Zn(NO3)2·6H2O in 100 mL of DMF, and dissolve 9 g of benzimidazole in 100 mL of absolute methanol. After ultrasonic dissolution, gradually mix the two and stir for 24 h using a constant temperature heating magnetic stirrer at 25 °C. Then centrifuge at 8000 rpm and remove the supernatant. Wash the final product with methanol, and then repeat centrifugation three times using a high-speed centrifuge, and wash with methanol each time. Dry the final product in a vacuum oven at 40 °C for 24 h to obtain pure white ZIF-7 powder;

[0061] S3. Take 0.5 g of Ti3C2T X MXene nanosheets and 0.1 g of ZIF-7 nanoparticles are respectively dissolved in 50 mL of ethanol by ultrasonic dissolution and then mixed and stirred for 24 h. Centrifuge at a speed of 3000 rpm for 2 min, and place the final product in a vacuum drying oven (40 °C) for 12 h to obtain MXene@ZIF-7 two-dimensional composite nanocontainers;

[0062] S4. Mix 5 mL of the ethanol suspension (10 mg / mL) of MXene@ZIF-7 two-dimensional composite nanocontainers with an aqueous curing agent obtained by mixing 3 g of polyetheramine D400 and polyetheramine D2000. Ultrasonically treat the mixture for 5 min and then stir with a glass rod for 10 min. Then add 2 g of EP resin (E-51), and then stir for 20 min. To ensure the denseness of the coating, degas the mixture in a vacuum oven at room temperature for 10 min. Finally, use a wire bar coater to coat the composite coating on the surface of a pretreated carbon steel electrode with a thickness of 80 ± 5 μm. Cure the coated electrode at room temperature for 12 h, and then put it into an oven at 60 °C for 12 h, and name it MXene@ZIF-7 / EP coating.

[0063] Example 3 : This example provides a preparation method of an anti-corrosion and wear-resistant coating with pH response.

[0064] S1. Slowly add 1.5 g of Ti3C2T X powder to an etching solution mixed with 30 mL of HCl and LiF, and stir magnetically at room temperature for 5 - 30 min. Then react at room temperature for 24 h. Wash the mixture with deionized water and centrifuge several times at 3500 rpm until the pH value of the supernatant is not less than 6. Then perform vacuum-assisted filtration using a polyvinylidene fluoride (PVDF) membrane with a pore size of 0.22 μm, and re-wash the MXene sediment with deionized water. Finally, freeze-dry the sediment in a vacuum for 24 h to obtain pure Ti3C2T X MXene nanosheets;

[0065] S2. Dissolve 3.2 g of Zn(NO3)2·6H2O in 100 mL of DMF, and dissolve 9 g of benzimidazole in 100 mL of anhydrous methanol. After ultrasonic dissolution, gradually mix the two and stir for 24 h using a constant-temperature heating magnetic stirrer at 25 °C. Subsequently, centrifuge at 8000 rpm and remove the supernatant. Wash the final product with methanol, and then repeat centrifugation three times using a high-speed centrifuge, each time washing with methanol. Dry the final product in a vacuum oven at 40 °C for 24 h to obtain pure white ZIF-7 powder;

[0066] S3. Take 0.5 g of Ti3C2T X MXene nanosheets and 0.05 g of ZIF-7 nanoparticles are respectively dissolved in 50 mL of ethanol by ultrasonic dissolution and then mixed and stirred for 24 h. Centrifuge at a speed of 3000 rpm for 2 min, and place the final product in a vacuum drying oven (40 °C) for 12 h to obtain MXene@ZIF-7 two-dimensional composite nanocontainers;

[0067] S4. Mix 5 mL of the ethanol suspension (10 mg / mL) of MXene@ZIF-7 two-dimensional composite nanocontainers with an aqueous curing agent mixture of 3 g of polyetheramine D400 and polyetheramine D2000. Ultrasonically treat the mixture for 5 min and then stir with a glass rod for 10 min. Subsequently, add 2 g of EP resin (E-51), and then stir for 20 min. To ensure the denseness of the coating, degas the mixture in a vacuum oven at room temperature for 10 min. Finally, use a wire bar coater to coat the composite coating on the surface of the pretreated carbon steel electrode with a thickness of 80 ± 5 μm. Cure the coated electrode at room temperature for 12 h, and then place it in an oven at 60 °C for 12 h, and name it MXene@ZIF-7 / EP coating.

[0068] Comparative Example 1

[0069] Compared with Example 1, this comparative example uses a two-dimensional composite nanocontainer without loaded ZIF-7.

[0070] S1. Slowly add 1.5 g of Ti3C2T X powder to the etching solution mixed with 30 mL of HCl and LiF, and stir magnetically at room temperature for 5 - 30 min. Then react at room temperature for 24 h. Wash the mixture with deionized water and centrifuge several times at 3500 rpm until the pH value of the supernatant is not less than 6. Then perform vacuum-assisted filtration using a polyvinylidene fluoride (PVDF) membrane with a pore size of 0.22 μm, and re-wash the MXene sediment with deionized water. Finally, freeze-dry the sediment under vacuum for 24 h to obtain pure Ti3C2T X MXene nanosheets;

[0071] S2. Mix the ethanol suspension of 5 mL of Ti3C2Tx MXene nanosheets (10 mg / mL) with 3 g of a water-based curing agent which is a mixture of polyetheramine D400 and polyetheramine D2000. After sonication of the mixture for 5 min, stir it with a glass rod for 10 min. Subsequently, add 2 g of EP resin (E-51), and then stir for 20 min. To ensure the denseness of the coating, degas the mixture in a vacuum oven at room temperature for 10 min. Finally, use a wire bar coater to coat the composite coating on the surface of the pretreated carbon steel electrode with a thickness of 80 ± 5 μm. Cure the coated electrode at room temperature for 12 h, and then put it into an oven at 60 °C for 12 h, and name it MXene / EP coating. X

[0072] Comparative Example 2 This comparative example provides a method for preparing an EP coating.

[0073] S1. Mix 2 g of EP resin (E-51) with 3 g of a water-based curing agent which is a mixture of polyetheramine D400 and polyetheramine D2000, and then stir for 20 min. To ensure the denseness of the coating, degas the mixture in a vacuum oven at room temperature for 10 min. Finally, use a wire bar coater to coat the composite coating on the surface of the pretreated carbon steel electrode with a thickness of 80 ± 5 μm.

[0074] S2. Cure the coated electrode at room temperature for 12 h, and then put it into an oven at 60 °C for 12 h, and name it EP coating.

[0075] Test Example 1

[0076] In this test example, electrochemical impedance spectroscopy (EIS) was used to study the corrosion inhibition performance of MXene@ZIF-7 two-dimensional composite nanocontainers on steel electrodes.

[0077] Figure 3 shows the variation of the impedance diagram of carbon steel in 3.5 wt% NaCl solution with and without nanocontainers (500 mg / L) over time. Generally, the electrochemical reactivity can be reflected by the impedance modulus (Z f = 0.01 Hz) in the low-frequency region. Therefore, in this test example, the interaction between the two-dimensional composite nanocontainers and the electrode surface was evaluated by collecting the change in impedance.

[0078] As Figure 3 shown in a1, the steel electrode showed a relatively low impedance value (the impedance value was lower than 569.4 Ω·cm) during the 12-h test in pure 3.5 wt% NaCl solution. 2 ​, (log value is 2.76). For the carbon steel substrate, the interaction with the electrolyte easily leads to the formation of micro-galvanic couples. The metal substrate is oxidized, losing electrons to produce metal ions. Then, the metal ions undergo hydrolysis reactions, resulting in acidification in the anodic region.

[0079] As Figure 3 shown in b1, the impedance value of the steel electrode slightly increases in the NaCl solution containing only MXene.

[0080] In contrast, as Figure 3 shown in c1, in the NaCl solution containing the MXene@ZIF-7 two-dimensional composite nanocontainer prepared in Example 1 of the present application, the typical impedance modulus of steel increases from 667.2 (log value is 2.82, 1 h) to 1600 Ω·cm 2 (log value is 3.20, 12 h), indicating that the metal oxidation process has been effectively inhibited by the two-dimensional composite nanocontainer.

[0081] In addition, the corrosion degree and failure process of different samples can also be analyzed through the changes in the phase angle diagram and Nyquist diagram. Generally, the micro-corrosion of the coating is closely related to the breakpoint frequency (f b ), and f b is defined as the frequency at -45° in the phase angle diagram. As can be seen from Figure 3 a2, b2, and c2, the f b containing two-dimensional nanocontainers is the lowest. As can be seen from Figure 3 a3, b3, and c3, the electrochemical results of the two-dimensional nanocontainers always maintain the largest capacitive reactance arc radius throughout the immersion period, indicating that the two-dimensional nanocontainers prepared by the present invention have relatively excellent corrosion inhibition performance.

[0082] According to the above discussion, it can be concluded that the synthesized MXene@ZIF-7 two-dimensional composite nanocontainer has pH-responsive characteristics. Or rather, local acidification stimulates the dissociation of the nanosensor to produce BIM, which can act as an inhibitor to protect the metal substrate from corrosion.

[0083] Test Example 2

[0084] In this test example, the changes in the corrosion inhibition performance (impedance value) of the two-dimensional composite nanocontainers formed by ZIF-7, ZIF-8, and ZIF-62 were tested and compared in a 3.5 wt% NaCl solution, and the test results are shown in Table 1.

[0085] Table 1 Test results of the slow-release performance

[0086]

[0087] As can be seen from Table 1, compared with the two-dimensional composite nanocontainers formed by ZIF-8 and ZIF-62, the change in the typical impedance modulus value of steel in the NaCl solution of the two-dimensional composite nanocontainer formed by ZIF-7 shows that it has a more excellent corrosion inhibition effect.

[0088] The organic ligand of ZIF-7 is benzimidazole. Such corrosion inhibitors are adsorption-type corrosion inhibitors, and their functional groups can bond with the metal surface through molecular interface adsorption, inhibition effect, group coverage effect, and hydrogen bond association effect, enabling benzimidazole molecules to adsorb on the metal surface and form a dense passivation film. In addition, due to its high porosity, ZIF-7 responds more rapidly to pH values, thus achieving a more excellent corrosion inhibition effect. The organic ligand of ZIF-8 is 2-methylimidazole. Due to its high bond energy, it is not conducive to the release of corrosion inhibitor molecules, resulting in its less sensitive response to pH values. The ligand of ZIF-62 is imidazole and benzimidazole. Due to the special structure of imidazole, it has certain hydrophobic properties, which seriously hinders its dissolution in aqueous solution, thus reducing its corrosion inhibition performance.

[0089] Test Example 3

[0090] In this test example, the friction coefficients of the coatings in Examples 1 to 3 and Comparative Examples 1 to 2 were tested. Specifically, by using an Rtec MFT-5000 multifunctional friction and wear testing machine, in the form of reciprocating friction, the loading force was set to 10 N for a 20-minute test. The test results are shown in Table 2.

[0091] Table 2 Friction Coefficient Test Results

[0092] Example / Comparative Example Coefficient of friction Wear rate Example 1 0.18 0.005 Example 2 0.2 0.013 Example 3 0.24 0.022 Comparative Example 1 0.21 0.018 Comparative Example 2 0.43 0.197

[0093] As can be seen from Table 2, the self-lubricating Ti3C2T x MXene nanosheets can resist severe plastic deformation, thereby reducing the wear rate of C-MXene. In addition, Ti3C2T x MXene nanosheets are prone to relative sliding, thus reducing the friction coefficient of the coating.

[0094] The anti-corrosion mechanism of the composite coatings in Examples 1 to 3 is as Figure 4 shown. In the early stage of service, the applied coating mainly plays its barrier role, extending the diffusion path of the electrolyte. After serving for a relatively long time, the corrosive medium will inevitably penetrate the coating and contact the metal matrix, thus generating a primary battery at the metal / coating interface. At this time, due to the hydrolysis of metal ions, a local acidic environment can be established in the anodic region, which dissociates the two-dimensional composite nanocontainer, enabling the MXene sheet loaded with ZIF-7 to respond and generate Zn 2+Ions and BIM active molecules. The generated iron ions can be rapidly captured by the detached BIM, so the free BIM can act as an inhibitor to effectively inhibit the further propagation at the local corrosion site.

[0095] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A pH-responsive anti-corrosion and wear-resistant coating, characterized in that, The pH-responsive anti-corrosion and wear-resistant coating is composed of composite nanocontainers, polymer resin and aqueous curing agent, and the composite nanocontainers are composed of two-dimensional MXene nanosheets and zeolitic imidazolate frameworks; Among them, the composite nanocontainers are prepared into an ethanol suspension of composite nanocontainers at 10 mg / mL, and the dosage ratio of the ethanol suspension of composite nanocontainers to polymer resin is 5 mL:2 g; In the composite nanocontainers, the mass ratio of zeolitic imidazolate framework to two-dimensional MXene nanosheets is 1:2 to 1:5; The two-dimensional MXene nanosheets are Ti3C2T x ; The zeolitic imidazolate framework is ZIF-7; The polymer resin is epoxy resin.

2. A preparation method of the anti-corrosion and wear-resistant coating with pH response as described in claim 1, characterized in that, It includes the following steps: S1. Add MAX powder to the etching solution for etching reaction to obtain MXene nanosheets; S2. Modify the MXene nanosheets with zeolitic imidazolate frameworks to obtain composite nanocontainers; S3. Mix the composite nanocontainers with polymer resin to form a composite coating.

3. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 2, characterized in that, In step S1, the MAX powder is Ti3AlC2; the etching solution is a mixed solution of HCl and LiF.

4. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 3, characterized in that, The time of the etching reaction is 24 h; the mixture obtained after the etching reaction needs to be successively washed with deionized water, centrifuged, filtered and freeze-dried.

5. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 4, characterized in that, The rotation speed of the centrifugation is set at 3500 rpm.

6. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 4, wherein, The pH value of the supernatant after centrifugation is not less than 6.

7. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 4, characterized in that The filtration is carried out by vacuum-assisted filtration using a polyvinylidene fluoride membrane with a pore size of 0.22 μm, and then the MXene deposit is washed again with deionized water.

8. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 4, characterized in that, The time of the freeze-drying is 24 h.

9. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 2, wherein In step S2, the zeolitic imidazolate framework is obtained by dissolving Zn(NO3)2·6H2O and benzimidazole respectively, mixing them for reaction, and then successively centrifuging, washing and drying.

10. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 9, characterized in that, The molar ratio of Zn(NO3)2·6H2O to benzimidazole is 1:

7.

11. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 9, characterized in that, Zn(NO3)2·6H2O is dissolved in DMF, and benzimidazole is dissolved in absolute methanol.

12. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 9, characterized in that, The time of the mixing reaction is 24 h.

13. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 9, characterized in that, The washing is carried out 2 to 4 times with an organic solvent.

14. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 13, wherein, The organic solvent is methanol.

15. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 9, wherein, The drying temperature is 40°C and the time is 24 h.

16. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 2, characterized in that, In step S2, the composite nanocontainers are obtained by dissolving MXene nanosheets and zeolitic imidazolate frameworks in ethanol respectively, mixing them for reaction, and then successively centrifuging and drying.

17. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 16, characterized in that, The mass ratio of MXene nanosheets to zeolitic imidazolate frameworks is 2:

1.

18. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 16, characterized in that, The time of the mixing reaction is 24 h.

19. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 16, characterized in that, The drying temperature is 40°C and the time is 12 h.

20. The preparation method of the anti-corrosion and wear-resistant coating with pH response according to claim 2, characterized in that, In step S3, the composite coating is obtained by reacting the ethanol suspension of composite nanocontainers, aqueous curing agent and polymer resin, and then successively carrying out degassing treatment, coating on the electrode, and electrode curing.

21. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 20, characterized in that, The mass ratio of the aqueous curing agent to polymer resin is 3:

2.

22. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 20, wherein, The time of the degassing treatment is 10 min.

23. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 20, characterized in that, The aqueous curing agent is a mixture of polyetheramine D400 and polyetheramine D2000.

24. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 20, characterized in that, The specific operation of the coating is as follows: use a wire bar coater to coat the composite coating on the surface of the pretreated carbon steel electrode with a thickness of 80 ± 5 μm.

25. The preparation method of the pH-responsive anti-corrosion and wear-resistant coating according to claim 20, characterized in that, The coated electrode is first cured at 25 °C for 12 h, and then the temperature is raised to 60 °C for 12 h.

26. Application of the anti-corrosion and wear-resistant coating with pH response as described in claim 1 in the deep sea.

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