A composite rust conversion material based on MXene modification and a preparation method thereof

Abstract

This invention relates to a composite rust-transfer material based on MXene modification and its preparation method, belonging to the field of chemical materials technology. The rust-transfer material is a ternary composite material composed of two-dimensional nanomaterial MXene, gallic acid, and phytic acid. MXene is first prepared by etching, and then the MXene-PA-GA composite rust-transfer material is prepared in situ using an ice-water bath method, which is the rust-transfer material of this invention. Phytic acid and gallic acid in the rust-transfer material are readily available, stable, and weakly acidic, with high density of the main rust-transferring functional groups phosphate and phenolic hydroxyl groups. The combination of these two substances with MXene can fully utilize the physical shielding ability of the two-dimensional nanomaterial MXene, enhance the corrosion protection performance of the substrate, reduce the acidity of the rust-transfer material, improve the long-term stability of the rust-transfer material, and construct an efficient rust-transfer and corrosion-resistant solution. The preparation method is simple, and the preparation conditions are controllable. The obtained rust-transfer material has a regular morphology, uniform loading, and good rust-transfer ability.

Description

Technical Field

[0001] This invention relates to an MXene-modified composite rust-converting material and its preparation method. Specifically, it relates to an MXene-modified composite rust-converting material that can be applied to the surface of rusted steel, can achieve rust conversion and improve corrosion resistance, and its preparation method belongs to the field of chemical materials technology. Background Technology

[0002] In modern industrial systems, steel structures, as the most widely used and consumed engineering structural material, face the pressing challenge of corrosion and protection. Currently, coatings remain the primary and most widely applied anti-corrosion technology. However, traditional anti-corrosion coating application typically requires sandblasting or shot blasting of the substrate to achieve a high rust removal grade (Sa2.5, i.e., a smooth, rust-free surface). But facing the harsh conditions of on-site maintenance of large engineering equipment and in some special engineering fields where sandblasting or shot blasting is difficult, it is challenging to meet the required rust removal grade on the substrate surface, significantly limiting the performance of traditional coatings. Therefore, rust-converting materials (also known as rust-converting agents), as intermediate substances that can be coated on the surface of rusted substrates with simple surface treatment or no treatment, to achieve a good bond between the substrate and the anti-corrosion coating and improve the corrosion protection performance of the coating, have attracted widespread attention from researchers.

[0003] Phosphate-based and tannic acid-based substances are widely used in the field of rust-transfer materials, but their excessive reactivity can cause secondary corrosion to the substrate and cannot further improve the substrate's corrosion protection capabilities, exhibiting significant limitations in practical applications. To address these issues, various methods can be used to modify phosphate-based and tannic acid-based substances. For example, combining amino substances with traditional acidic substances can not only reduce the acidity of the rust-transfer material but also increase the density of rust-transfer functional groups, achieving a more efficient rust-transfer process. In their paper "Synthesis of 3,4,5-trihydroxy-2-[(hydroxyimino)methyl]benzoic acid as a novel rust converter," Feng et al. investigated a modification method for gallic acid. They grafted hydroxyimino groups onto 3,4,5-trihydroxybenzoic acid (i.e., gallic acid) to obtain a novel rust inhibitor—3,4,5-trihydroxy-2-[(hydroxyimino)methyl]benzoic acid. Salt spray tests demonstrated its excellent anti-corrosion properties, enabling it to form a relatively dense passivation film on the substrate surface, preventing the penetration of water molecules and chloride ions. Therefore, modification with phosphoric acid and tannic acid-based substances can effectively enhance the rust conversion efficiency of rust-converting materials, improve the corrosion resistance of the substrate, and construct a more long-lasting corrosion protection layer, which is of great significance for promoting the development of rust conversion technology. Summary of the Invention

[0004] To address the problems of high activity and strong acidity, but low rust-transfer efficiency and weak long-term stability of traditional phosphoric acid and tannic acid-based rust-transfer materials, this invention aims to provide a composite rust-transfer material based on MXene modification and its preparation method. The rust-transfer material is a compound of phytic acid and gallic acid, combined with the two-dimensional nanomaterial MXene. Phytic acid and gallic acid are readily available, stable, and weakly acidic, with a high density of their main rust-transfer functional groups (phosphate and phenolic hydroxyl groups). Simultaneously, the combination of these two substances with MXene fully utilizes the physical shielding ability of the MXene two-dimensional nanomaterial, enhancing the corrosion protection performance of the substrate, reducing the acidity of the rust-transfer material, improving its long-term stability, and constructing an efficient rust-transfer and corrosion-prevention solution.

[0005] To achieve the objectives of this invention, the following technical solutions are provided.

[0006] A composite rust-transforming material based on MXene modification, wherein the rust-transforming material is a ternary composite material composed of two-dimensional transition metal carbide (MXene), gallic acid (GA) and phytic acid (PA); The mass ratio of MXene, gallic acid and phytic acid is 1.0 ~ 1.5 : 0.25 ~ 0.35 : 1.5 ~ 2.5.

[0007] A method for preparing a composite rust-converting material based on MXene modification according to the present invention, the steps of which are as follows: MXene was first prepared by etching, and then MXene-PA-GA composite rust-transforming material was prepared in situ by ice-water bath method, which is a composite rust-transforming material based on MXene modification as described in this invention.

[0008] Specifically, the steps for preparing MXene by etching are as follows: LiF was slowly added to the hydrochloric acid solution to form a homogeneous solution. Then, titanium aluminum carbide (MAX) was slowly added over 30 min, and the mixture was continuously stirred in a water bath to remove the aluminum layer. The precipitate was centrifuged and washed until the pH value was greater than 6. Then, it was filtered and dried to obtain the powder product, which is MXene.

[0009] Furthermore, the hydrochloric acid solution has a mass fraction of 32% to 38%, i.e., a molar concentration of 10 mol / L to 12 mol / L; both LiF and MAX are powders, and based on the mass of the hydrochloric acid solution as 100%, the mass fraction of LiF is 4% to 5% of the mass of the hydrochloric acid solution, and the mass fraction of MAX is 4% to 5% of the mass of the hydrochloric acid solution. Furthermore, under water bath conditions, the continuous stirring rate is 400 r / min ~ 600 r / min, the water bath temperature is 35 ℃ ~ 45 ℃, and the time is 24 h ~ 48 h; The centrifugation speed for sedimentation is 4000 r / min ~ 6000 r / min; Washing involves first adding water to the precipitate, then adding anhydrous ethanol, and repeating the washing process several times. Drying is carried out in a vacuum at 30℃~40℃ for 4h~6h.

[0010] Specifically, the steps for in-situ preparation of MXene-PA-GA composite rust-transforming materials using the ice-water bath method are as follows: Gallic acid and phytic acid were dissolved in ice water and ultrasonically treated under ice-water bath conditions. Then, MXene was slowly added to the mixture and stirred thoroughly under ice-water bath conditions to allow the reaction to proceed, thus obtaining the MXene-PA-GA composite rust-transfer material.

[0011] Based on the mass of ice water as 100%, the mass fraction of gallic acid is 0.25% to 0.35% of the mass of ice water, the mass fraction of phytic acid is 1.5% to 2.5% of the mass of ice water, and the mass fraction of MXene is 1.0% to 1.5% of the mass of ice water. The duration of the ice-water bath ultrasonic treatment is 20 min to 30 min, and the ultrasonic power is 150 W to 200 W. The stirring speed during the grafting reaction was 400 r / min ~ 600 r / min, and the stirring time was 4 h ~ 6 h.

[0012] The basic principle of this invention is as follows: Gallic acid is a small-molecule monomer of tannic acid, characterized by its stability, weaker acidity compared to tannic acid, and readily available raw materials. Phytic acid, on the other hand, is characterized by its readily available raw materials, high stability, and strong complexing ability. The phenolic hydroxyl functional group in gallic acid and the polyphosphate structure in phytic acid can respectively undergo complexation reactions with different configurations of corrosive substances, inertly transforming the corrosive substances and fixing them on the substrate surface to form a relatively smooth and dense rust-transfer material, preventing further corrosion of the substrate. Simultaneously, the carboxyl groups on both acidic substances can undergo grafting reactions with the hydroxyl and other functional groups on the two-dimensional lamellar structure inside the MXene material, introducing MXene into the rust-transfer material. This reduces the acidity of the rust-transfer material, increasing its long-term stability, and also endows it with excellent physical shielding properties, further isolating external water and oxygen molecules through the labyrinth effect, thereby increasing the substrate's corrosion resistance.

[0013] Beneficial effects (1) This invention provides a composite rust-transforming material based on MXene modification and its preparation method. The MXene-PA-GA composite rust-transforming material is prepared in situ by ice-water bath method. The method is simple and the preparation conditions are controllable. The obtained rust-transforming material has the characteristics of regular microstructure and uniform load, and has good rust-transforming ability. (2) The present invention provides a composite rust-converting material based on MXene modification and its preparation method, wherein the phenolic hydroxyl groups and phosphate groups of gallic acid and phytic acid can be fully inertly converted against common different types of rust substances to form substances such as iron gallate and iron phytate, thereby reducing the reactivity of rust substances. (3) The present invention provides a composite rust-converting material based on MXene modification and its preparation method. The rust-converting material is applied to the surface of a rusted substrate, and the resulting iron gallate and iron phytate can adhere to the surface of the substrate to form a rust-converting material layer. At the same time, MXene can fill the defects of the rust-converting material layer and increase the physical shielding ability of the rust-converting material layer, forming a relatively flat and dense rust-converting material layer on the surface of the substrate. (4) This invention provides a composite rust-transfer material based on MXene modification and its preparation method. After applying the rust-transfer material to the surface of a rust-corroded substrate, an epoxy resin is coated to form a composite rust-transfer coating. In EIS testing, after the rust-transfer coating is immersed in a 3.5% NaCl solution for 60 days, the impedance modulus |Z| 0.01Hz 1.57×10 9 Ω·cm 2 It has good corrosion resistance; (5) The present invention provides a composite rust-converting material based on MXene modification and its preparation method. After the rust-converting material is applied to the surface of the rust-corroded substrate, an epoxy resin is coated to form a rust-converting coating. In the neutral salt spray test, no obvious corrosion phenomenon was observed after 720 h, indicating that the rust-converting material has outstanding corrosion protection ability. Attached Figure Description

[0014] Figure 1 The scanning electron microscope and energy-dispersive X-ray spectra of a composite rust-transfer material based on MXene modification prepared in Example 1 are shown. Figure 2 These are cobalt target X-ray diffraction images of the substrate surface before and after treatment with a composite rust-transfer material based on MXene modified in Example 1. Figure 3 These are scanning electron microscope images of the substrate surface before and after treatment with a composite rust-removing material based on MXene modified by Example 1. Figure 4 Neutral salt spray test images of the rust-transforming coatings described in Examples 1 and 2 and Comparative Examples 1 and 2; Figure 5 The impedance test comparison diagrams are shown for the rust-transforming coatings described in Examples 1 and 2 and Comparative Examples 1 and 2. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the present invention.

[0016] In Examples 1 and 2 and Comparative Examples 1 and 2 below, the mass fraction of the hydrochloric acid solution is 36%.

[0017] Example 1 A method for preparing a composite rust-converting material based on MXene modification is as follows: (1) Preparation of MXene by etching method First, 0.93 g of LiF was slowly added to 20 mL of a 10 mol / L hydrochloric acid solution, so that the mass fraction of LiF was 4% of the mass of the hydrochloric acid solution, forming a homogeneous solution. Then, 0.93 g of MAX powder was added uniformly over 30 min, so that the mass fraction of MAX was 4% of the mass of the hydrochloric acid solution. The aluminum layer was removed by continuous stirring at 400 r / min for 24 h in a water bath at 35 ℃. Then, the precipitate was centrifuged at 4000 r / min for 5 min. The precipitate was washed with deionized water and then with anhydrous ethanol, and the washing was repeated until the pH value was greater than 6. The precipitate was then filtered, and the solid obtained by filtration was dried in a vacuum oven at 30 ℃ for 4 h to obtain 0.37 g of MXene powder. (2) In-situ preparation of MXene-PA-GA composite rust-converting material by ice-water bath method 0.05 g gallic acid powder and 0.6 g phytic acid aqueous solution with a mass fraction of 50% were added to 20 ml of ice water, so that the mass fraction of gallic acid was 0.25% of the mass of ice water and the mass fraction of phytic acid was 1.5% of the mass of ice water. The mixture was treated with an ultrasonic power of 150W for 20 min under ice water bath conditions. Then, 0.2 g of MXene powder prepared in step (1) was added at a constant rate over 20 min, so that the mass fraction of MXene was 1.0% of the mass of ice water. The mixture was stirred at 400 r / min for 4 h to allow it to react fully, and an MXene-PA-GA composite rust-transforming material was obtained, which is the composite rust-transforming material based on MXene modification described in this invention.

[0018] To further evaluate the corrosion resistance, the rust-reducing material prepared in this embodiment was used to treat the rusted substrate, and an epoxy resin coating was applied to evaluate the differences in corrosion resistance. The specific method is as follows: The rust-transforming material prepared in this embodiment is uniformly coated onto the surface of a low-carbon steel rust-corroded substrate and dried at room temperature for 30 minutes. After the moisture evaporates naturally, a uniform rust-transforming layer is formed on the surface of the substrate, which is called the rust-transforming substrate. Add 0.75 g of curing agent T-31 to 5 g of E-20 epoxy resin (solid content 60%), so that the mass ratio of E-20 epoxy resin to curing agent T-31 is 4:1. Stir for 20 min to fully mix to obtain epoxy resin coating. Apply epoxy resin coating to the surface of rust-transfer substrate using a thin film coating machine. After drying and curing at room temperature for 1 day, an MXene modified composite rust-transfer coating with a dry film thickness of 100 μm is obtained, named MP-G1.0 / EP.

[0019] Example 2 A method for preparing a composite rust-converting material based on MXene modification is as follows: (1) Preparation of MXene by etching method First, 1.2 g of LiF was slowly added to 20 mL of 12 mol / L hydrochloric acid solution to make the mass fraction of LiF 5% of the mass of hydrochloric acid solution, forming a homogeneous solution. Then, 1.2 g of MAX powder was added uniformly over 30 min to make the mass fraction of MAX 5% of the mass of hydrochloric acid solution. The aluminum layer was removed by continuous stirring at 600 r / min for 48 h in a water bath at 45 ℃. Then, the precipitate was centrifuged at 6000 r / min for 5 min. The precipitate was washed with deionized water and then with anhydrous ethanol. The washing was repeated until the pH value was greater than 6. The precipitate was then filtered, and the solid obtained by filtration was dried in a vacuum oven at 40 ℃ for 6 h to obtain 0.51 g of MXene powder. (2) In-situ preparation of MXene-PA-GA composite rust-converting material by ice-water bath method 0.07 g gallic acid powder and 1.0 g phytic acid aqueous solution with a mass fraction of 50% were added to 20 ml of ice water, so that the mass fraction of gallic acid was 0.35% of the mass of ice water and the mass fraction of phytic acid was 2.5% of the mass of ice water. The mixture was treated with an ultrasonic power of 200 W for 30 min under ice water bath conditions. Then, 0.3 g of MXene powder prepared in step (1) was added at a constant rate over 30 min, so that the mass fraction of MXene was 1.5% of the mass of ice water. The mixture was stirred at 600 r / min for 6 h to allow it to react fully, and an MXene-PA-GA modified composite rust-transfer material was obtained, which is the MXene-modified composite rust-transfer material described in this invention.

[0020] To further evaluate the corrosion resistance, the rust-reducing material prepared in this embodiment was used to treat the rusted substrate, and an epoxy resin coating was applied to evaluate the differences in corrosion resistance. The specific method is as follows: The rust-transforming material prepared in this embodiment is uniformly coated onto the surface of a low-carbon steel rust-corroded substrate and dried at room temperature for 30 minutes. After the moisture evaporates naturally, a uniform rust-transforming layer is formed on the surface of the substrate, which is called the rust-transforming substrate. Add 0.75 g of curing agent T-31 to 5 g of E-20 epoxy resin (solid content 60%), so that the mass ratio of E-20 epoxy resin to curing agent T-31 is 4:1. Stir for 20 min to fully mix to obtain epoxy resin coating. Apply epoxy resin coating to the surface of rust-transfer substrate using a thin film coating machine. After drying and curing at room temperature for 1 day, an MXene modified composite rust-transfer coating with a dry film thickness of 100 μm is obtained, named MP-G1.5 / EP.

[0021] Comparative Example 1 A method for preparing a composite rust-converting material based on MXene modification is as follows: (1) Preparation of MXene by etching method Same as step (1) in Example 1; (2) In-situ preparation of MXene-PA-GA composite rust-converting material by ice-water bath method 0.03 g gallic acid powder and 0.4 g phytic acid aqueous solution with a mass fraction of 50% were added to 20 ml of ice water, so that the mass fraction of gallic acid was 0.15% of the mass of ice water and the mass fraction of phytic acid was 1% of the mass of ice water. The mixture was treated with an ultrasonic power of 100 W for 30 min under ice water bath conditions. Then, 0.1 g of MXene powder prepared in step (1) was added at a constant rate over 30 min, so that the mass fraction of MXene was 0.5% of the mass of ice water. The mixture was stirred at 400 r / min for 4 h to allow it to react fully, and an MXene-PA-GA modified composite rust-transfer material was obtained, which is a composite rust-transfer material based on MXene modification.

[0022] To further evaluate the corrosion resistance, the rust-transforming material prepared in this comparative example was used to treat the rusted substrate, and an epoxy resin coating was applied to evaluate the differences in corrosion resistance; the specific method is as follows: The rust-transforming material prepared in this embodiment is uniformly coated onto the surface of a low-carbon steel rust-corroded substrate and dried at room temperature for 30 minutes. After the moisture evaporates naturally, a uniform rust-transforming layer is formed on the surface of the substrate, which is called the rust-transforming substrate. Add 0.75 g of curing agent T-31 to 5 g of E-20 epoxy resin (solid content 60%), so that the mass ratio of E-20 epoxy resin to curing agent T-31 is 4:1. Stir for 20 min to fully mix to obtain epoxy resin coating. Apply epoxy resin coating to the surface of rust-transfer substrate using a thin film coating machine. After drying and curing at room temperature for 1 day, an MXene modified composite rust-transfer coating with a dry film thickness of 100 μm is obtained, named MP-G0.5 / EP.

[0023] Comparative Example 2 A method for preparing a composite rust-converting material based on MXene modification is as follows: (1) Preparation of MXene by etching method Same as step (1) in Example 2; (2) In-situ preparation of MXene-PA-GA composite rust-converting material by ice-water bath method 0.1 g gallic acid powder and 1.4 g phytic acid aqueous solution with a mass fraction of 50% were added to 20 ml of ice water, so that the mass fraction of gallic acid was 0.5% of the mass of ice water and the mass fraction of phytic acid was 3.5% of the mass of ice water. The mixture was treated with an ultrasonic power of 250 W for 30 min under ice water bath conditions. Then, 0.4 g of MXene powder prepared in step (1) was slowly added over 30 min, so that the mass fraction of MXene was 2.0% of the mass of ice water. The mixture was stirred at 600 r / min for 6 h to allow it to react fully, and an MXene-PA-GA modified composite rust-transfer material was obtained, which is a composite rust-transfer material based on MXene modification.

[0024] To further evaluate the corrosion resistance, the rust-transforming material prepared in this comparative example was used to treat the rusted substrate, and an epoxy resin coating was applied to evaluate the differences in corrosion resistance; the specific method is as follows: The rust-transforming material prepared in this embodiment is uniformly coated onto the surface of a low-carbon steel rust-corroded substrate and dried at room temperature for 30 minutes. After the moisture evaporates naturally, a uniform rust-transforming layer is formed on the surface of the substrate, which is called the rust-transforming substrate. Add 0.75 g of curing agent T-31 to 5 g of E-20 epoxy resin (solid content 60%), so that the mass ratio of E-20 epoxy resin to curing agent T-31 is 4:1. Stir for 20 min to fully mix to obtain epoxy resin coating. Apply epoxy resin coating to the surface of rust-transforming substrate using a thin film coating machine. After drying and curing at room temperature for 1 day, an MXene modified composite rust-transforming coating with a dry film thickness of 100 μm is obtained, named MP-G2.0 / EP.

[0025] Test Analysis Experiment The rust-transforming materials prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the rusted substrates before and after treatment with the rust-transforming materials, and the rust-transforming coatings were tested. The test methods and results are as follows: (1) Microscopic morphology, structure and material composition testing The rust-transforming material prepared in Example 1 was characterized using a Gemini SEM 300 scanning electron microscope. The scanning electron microscope and energy-dispersive X-ray spectra are shown below. Figure 1 As shown; where, Figure 1 Figures a and b on the left are surface and cross-sectional images of the rust-transforming material, respectively. It can be seen that the rust-transforming material exhibits a sheet-like stacking with relatively large interlayer spacing. Figure 1 The right side shows its elemental distribution image, revealing that the Ti, P, C and O components in the rust-transforming material are uniformly distributed, further confirming the successful grafting of PA and GA materials; the rust-transforming material described in this invention was successfully prepared and has the characteristic of regular microstructure; the rust-transforming material prepared in Example 2 was characterized, and the results were similar to those in Example 1; The surfaces of the rust-corroded substrate in Example 1 before and after treatment with the described rust-transfer material were examined using a D8 Advance cobalt target X-ray diffractometer. The results are as follows: Figure 2 As shown in the figure; where the horizontal axis is the diffraction angle and the vertical axis is the absorption intensity, the yellow and blue lines represent the diffraction images before and after the rust transformation, respectively. It can be seen that before the rust transformation, the surface of the rusted substrate, in addition to the strong peak of elemental iron, also has many peaks of different rust types. After the rust transformation, the peaks of various iron oxides representing rust disappear, indicating that the rust-transforming material reacts fully with the rust and can transform various rust products of different crystal forms into inert complexes that cover the substrate surface. Most of the transformation products exist in an amorphous manner, revealing that the rust-transforming material described in this invention has good rust-transforming ability. The surface of the substrate before and after treatment with the rust-transforming material in Example 2 was tested, and the results were similar to those in Example 1. The surfaces of the rust-converting substrate in Example 1 before and after treatment with the aforementioned rust-converting material were examined using a Gemini SEM 300 scanning electron microscope. The scanning electron microscope images and energy-dispersive X-ray spectra are shown below. Figure 3 As shown; where, Figure 3 a and Figure 3Figure b shows the surface morphology of the rusted substrate before the rust-transfer treatment at different scales of 20 micrometers and 2 micrometers, respectively. The surface exhibits a loose and porous structure, indicating that the rust material is relatively loosely distributed on the substrate surface, with a large porosity, and cannot resist the invasion of corrosive substances. Figures c and d are surface and cross-sectional images of the rusted substrate after the rust-transfer treatment, respectively. It can be seen that the rust-transfer material chelates with the rust products on the surface of the rusted substrate, transforming them into a dense complex, thereby protecting the internal metal substrate from further corrosion. The surface of the substrate before and after treatment with the rust-transfer material in Example 2 was inspected, and the results were similar to those in Example 1.

[0026] (2) Mechanical property testing The mechanical properties of the rust-transfer coatings prepared in Examples 1 and 2, and Comparative Examples 1 and 2 were tested: Test methods: Coating adhesion was tested according to standard GB / T31586.1-2015, "Paint Film Pull-Off Test"; Coating adhesion was tested according to standard GB / T1732. The impact resistance of coatings is tested using the "2020 Test Method for Impact Resistance of Coatings"; refer to the standard "GB / T / 1731". The "1993 Test Method for Coating Flexibility" tests the flexibility of coatings. Results and Analysis: The test results of the examples and comparative examples show that the rust-transforming coatings prepared in Examples 1 and 2 have better mechanical properties, and their adhesion, impact resistance and flexibility are better than those prepared in Comparative Examples 1 and 2. The specific results are shown in Table 1. Therefore, the amount of MXene, gallic acid, and phytic acid added affects the mechanical properties of the rust-transfer coating: when the amount of the three substances added is too small and the concentration of the rust-transfer material is low, the rust-transfer material does not fully transfer the rust to the rust substrate, and the loose and porous morphology of the rust substrate surface is difficult to completely transform, resulting in a reduction in the contact area between the epoxy resin and the rust substrate, leading to a decrease in the mechanical properties of the coating; while when the amount of the three substances added is too large and the concentration of the rust-transfer material is high, gallic acid and phytic acid will cause secondary corrosion of the rust substrate, reducing the contact area between the epoxy resin and the rust substrate, leading to a decrease in the mechanical properties of the rust-transfer coating.

[0027] Table 1. Test results of mechanical properties of the rust-transforming coatings prepared in the examples and comparative examples.

[0028] (2) Corrosion resistance test The corrosion resistance of the rust-transfer coatings prepared in Examples 1 and 2, and Comparative Examples 1 and 2, was tested as follows: ① Neutral Salt Spray Test (NSS) Neutral salt spray testing was conducted in a salt spray chamber (Shanghai Yiheng Instrument Co., Ltd.). The temperature in the salt spray chamber was 35 ± 1 ℃, the pressure was 1.5 MPa, and the mass fraction of the salt water used was 5.0 ± 0.5%. The surface condition of the rust-transforming coating was recorded at regular intervals using an optical camera. Test photos are shown below. Figure 4 As shown.

[0029] Figure 4 The image records optical photographs taken after different durations of neutral salt spray testing. The scratches show signs of rust, and the overall whitening of the coating indicates reduced adhesion between the coating and the rust-transformed layer, resulting in decreased corrosion resistance and the appearance of corrosion. In summary, after 720 hours of salt spray testing, Comparative Examples 1 and 2 showed obvious brownish-red rust at the scratches, along with significant whitening, indicating a tendency to corrode. In Examples 1 and 2, after 720 hours of salt spray testing, only a small amount of brownish-red rust appeared at the scratches; the samples retained their initial bluish-black color without whitening, demonstrating good rust-transformation and corrosion protection effects.

[0030] ② Electrochemical performance testing Electrochemical impedance spectroscopy (EIS) was used for testing, and the specific method is as follows: A standard three-electrode system was used, with the working electrode being the rust-coated sample, the counter electrode being a platinum electrode, and the reference electrode being a saturated calomel electrode (SCE). The electrodes were placed 1 cm apart. The electrolyte solution was simulated seawater, specifically a 3.5% (w / w) NaCl aqueous solution. The testing environment was room temperature (25 ± 1 ℃). Electrochemical impedance spectroscopy (EIS) was performed using an Autolab electrochemical workstation and Nova 2.1. All electrochemical measurements were taken at open-circuit potential by applying a controllable AC perturbation signal (10 mV). -2 ~ 10 5 Impedance response was collected within the Hz frequency range; the corrosion resistance of the coating was evaluated using electrochemical impedance spectroscopy obtained from simulated seawater immersion tests, and the relationship between the magnitude of the impedance modulus and the frequency in the Nyquist spectrum was used as the basis for assessing the corrosion protection performance of the rust-converting material.

[0031] Results and Analysis: The electrochemical impedance spectroscopy of the rust-transforming coating is shown in [reference needed]. Figure 5 ; Figure 5Figures a, 5b, 5c, and 5d show the 60-day impedance test comparisons for Examples 1, 2, Comparative Example 1, and Comparative Example 2, respectively. The subscript 1 indicates a Nyquist plot, and the subscript 2 indicates a Bode plot. The Nyquist plot uses the real part of the impedance on the horizontal axis and the imaginary part on the vertical axis. The Bode plot uses frequency and amplitude (|Z|) as the horizontal and vertical axes, respectively. The results showed that the rust-transforming coatings prepared in Comparative Examples 1 and 2 could only reach an initial low-frequency impedance modulus of 10. 9 Ω cm 2 The impedance decrease was significantly greater than that of the rust-transforming coatings prepared in Examples 1 and 2. Both exhibited double arcing (corrosion) after approximately 30 days of immersion, demonstrating poor corrosion resistance. In contrast, the rust-transforming coatings prepared in Examples 1 and 2 had an initial low-frequency impedance modulus reaching 10. 10 Ω cm 2 The above results show that the corrosion resistance of the rust-converting coating prepared in Examples 1 and 2 is one order of magnitude higher than that of the rust-converting coating prepared in the comparative example, and no double arc phenomenon was observed after immersion for 60 days, indicating that the rust-converting coating prepared in Examples 1 and 2 has excellent anti-corrosion performance.

[0032] The above results show that when the contents of MXene, gallic acid, and phytic acid are low, and the concentration of the rust-transfer material is low, the rust-transfer effect is incomplete, and MXene cannot fully exert its barrier effect. When the contents of the three substances are high, and the concentration of the rust-transfer material is high, gallic acid and phytic acid will corrode the substrate, and the high conductivity of MXene will accelerate the corrosion of the substrate, reducing the corrosion resistance of the rust-transfer coating. The amount of each of the three substances added to the rust-transfer material described in this invention will affect the rust-transfer performance of the rust-transfer material and the corrosion resistance of the rust-transfer coating. A suitable composite ratio will improve the rust-transfer performance and the corrosion resistance of the coating.

[0033] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A composite rust-converting material based on MXene modification, characterized in that: The rust-transforming material is a ternary composite material composed of two-dimensional nanomaterials MXene, gallic acid, and phytic acid.

2. The composite rust-transfer material based on MXene modification according to claim 1, characterized in that: The mass ratio of MXene, gallic acid and phytic acid is 1.0 ~ 1.5 : 0.25 ~ 0.35 : 1.5 ~ 2.

5.

3. A method for preparing a composite rust-converting material based on MXene modification as described in claim 1 or 2, characterized in that: MXene was first prepared by etching, and then MXene-PA-GA composite rust-transforming material was prepared in situ by ice-water bath method, which is a composite rust-transforming material based on MXene modification.

4. The method for preparing a composite rust-converting material based on MXene modification according to claim 3, characterized in that: The steps for preparing MXene by etching are as follows: LiF was added to hydrochloric acid solution to form a homogeneous solution; then MAX was added over 30 min and stirred continuously in a water bath; the precipitate was centrifuged and washed until the pH value was greater than 6, then filtered and dried to obtain the powder product, which is MXene.

5. A method for preparing a composite rust-converting material based on MXene modification according to claim 4, characterized in that: The mass fraction of the hydrochloric acid solution is 32% to 38%; based on the mass of the hydrochloric acid solution as 100%, the mass fraction of LiF is 4% to 5% of the mass of the hydrochloric acid solution, and the mass fraction of MAX is 4% to 5% of the mass of the hydrochloric acid solution.

6. A method for preparing a composite rust-converting material based on MXene modification according to claim 4 or 5, characterized in that: The stirring speed in the water bath is 400 r / min ~ 600 r / min, the water bath temperature is 35 ℃ ~ 45 ℃, and the time is 24 h ~ 48 h; the centrifugal sedimentation speed is 4000 r / min ~ 6000 r / min. Washing involves adding water to the precipitate first, then adding anhydrous ethanol, and repeating the washing process several times. Drying is carried out in a vacuum at 30 ℃~40 ℃ for 4 h~6 h.

7. The method for preparing a composite rust-converting material based on MXene modification according to claim 3, characterized in that: The steps for in-situ preparation of MXene-PA-GA composite rust-transforming materials using the ice-water bath method are as follows: Gallic acid and phytic acid were dissolved in ice water and ultrasonically treated under ice-water bath conditions. Then, MXene was added and the mixture was stirred thoroughly under ice-water bath conditions to allow the reaction to proceed, thus obtaining the MXene-PA-GA composite rust-transfer material.

8. A method for preparing a composite rust-converting material based on MXene modification according to claim 7, characterized in that: Based on the mass of ice water as 100%, the mass fraction of gallic acid is 0.25% to 0.35% of the mass of ice water, the mass fraction of phytic acid is 1.5% to 2.5% of the mass of ice water, and the mass fraction of MXene is 1.0% to 1.5% of the mass of ice water.

9. A method for preparing a composite rust-converting material based on MXene modification according to claim 7 or 8, characterized in that: The duration of the ice-water bath ultrasonic treatment was 20 to 30 minutes, and the ultrasonic power was 150 W to 200 W. The stirring speed during the grafting reaction was 400 r / min ~ 600 r / min, and the stirring time was 4 h ~ 6 h.

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