An acid-doped polyaniline and a method for preparing the same, and an anticorrosive coating

Abstract

The present application relates to the field of anticorrosive materials, in particular to an acid-doped polyaniline, a preparation method thereof and an anticorrosive paint. The preparation method of the acid-doped polyaniline provided by the present application comprises the following steps: reacting polyaniline with a specific organic acid in a solvent medium, then performing solid-liquid separation, washing and drying the obtained solid product to obtain the acid-doped polyaniline. The acid-doped polyaniline obtained by the present application has a small particle size and a high doping degree, and when used in the anticorrosive paint, the acid-doped polyaniline has a high dispersibility when mixed with resin, a good anticorrosive effect and a good adhesion. Moreover, the acid-doped polyaniline obtained by the present application has a low addition amount, thereby reducing the production cost and expanding the application range. In addition, the preparation method of the present application is simple and has a low preparation cost.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion materials, and particularly to an acid-doped polyaniline, its preparation method, and an anti-corrosion coating. Background Technology

[0002] Polyaniline's unit composition consists of phenylenediamine and quinone diimide. The proportions of these two components vary depending on the oxidation state of the polyaniline. The most extensively studied and widely used form is intermediate-state polyaniline, which has three benzene rings and one quinone ring as its repeating unit. As one of the most promising conductive polymers, polyaniline has been studied extensively since its inception. When Mengoli et al. attempted to electrochemically polymerize aniline onto iron sheets to form polyaniline films, they discovered that the synthesized polyaniline films exhibited a certain degree of corrosion resistance to metallic iron. Since then, researchers have gradually begun to explore the applications of polyaniline in the field of corrosion protection. Polyaniline is simple to synthesize, stable in properties, and does not suffer from heavy metal pollution. Anti-corrosion coatings prepared by mixing appropriate amounts of polyaniline with other additives have wide applications in bridges, highways, and even marine and aerospace industries.

[0003] Early experiments with polyaniline for corrosion protection primarily involved electrochemical methods to uniformly form a film of polyaniline on metal surfaces, resulting in a film with good corrosion resistance. In 1985, Professor Deberry electrochemically polymerized a polyaniline film on stainless steel, allowing the metal surface to maintain a passivated state for hours ranging from several hours to 1200 hours, demonstrating excellent corrosion resistance. However, pure polyaniline films have poor adhesion to metals and are prone to peeling off. Furthermore, the resulting polyaniline films lack density and cannot physically shield the metal from external corrosive elements. In addition, the cost of electrochemically prepared polyaniline films prevents large-scale commercialization. Therefore, while electrochemical methods can achieve films with good corrosion resistance, chemical synthesis of polyaniline remains the most promising approach. Anti-corrosion coatings prepared by mixing chemically synthesized polyaniline with matrix materials such as resins or polyurethane can combine the adhesion and shielding properties of resins with the excellent corrosion resistance of polyaniline.

[0004] Wesslin applied a chemically synthesized polyaniline dispersion to the surface of low-carbon steel. After coating, the corrosion potential increased significantly, by 800 mV compared to uncoated low-carbon steel of the same specifications. After the polyaniline film had formed for a period of time, it was removed, revealing that the metal still possessed a certain degree of corrosion resistance. Using polyvinyl alcohol-doped sulfonated polyaniline as a water-based anti-corrosion material, its anti-corrosion performance was tested electrochemically in a 3% sodium chloride solution. Compared to bare metal plates, the metal plate coated with the anti-corrosion material showed a significant positive shift in corrosion potential, with a corrosion efficiency reaching 84.39%.

[0005] The use of multiple materials in combination can significantly enhance the anti-corrosion effect of materials. Commonly used inorganic materials include silica, graphene, and montmorillonite. Polyaniline is polymerized in situ on inorganic materials, relying on the nanoscale size and mechanical properties of the inorganic materials to achieve nanoscale dispersion of polyaniline. In situ polymerization of aniline on graphene oxide (GO) yields GO-Pani nanosheets. Graphene oxide possesses excellent barrier properties; by modifying graphene oxide, its agglomeration problem can be reduced. In situ polymerization of aniline on graphene oxide significantly enhances the barrier properties of the composite coating. Cerium oxide is considered a substitute for the traditional corrosion inhibitor chromate. GO-Pani-CeO hybrid coatings, prepared by mixing cerium oxide with GO-Pani nanosheets, showed excellent anti-corrosion effects in electrochemical tests.

[0006] Polyaniline was doped with three different acids—sulfuric acid, p-toluenesulfonic acid, and sulfonyl salicylic acid—to obtain polyaniline powders with different doping states. The three doped polyanilines were immersed in a 3.5% sodium chloride solution, and the changes in impedance values ​​over 100 days were measured using electrochemical impedance spectroscopy. The sulfuric acid-doped polyaniline showed the best impedance at initial time |Z| at 10... 10 The above indicates that p-toluenesulfonic acid-doped polyaniline is close to 10. 12 sulfonyl salicylic acid-doped polyaniline at 10 11 In the above analysis, sulfonyl salicylic acid showed the lowest degradation rate during 100 days of immersion, demonstrating the best anti-corrosion performance. However, traditional acid-doped polyaniline manufacturing does not pay enough attention to the doping process. The doping process requires excessive amounts of acid, excessively long doping times, and excessively high doping temperatures, resulting in a waste of resources and time. Furthermore, the doping effect is poor, and the doping degree is low, preventing the acid-doped polyaniline from achieving the maximum reduction in particle size. Summary of the Invention

[0007] In view of this, the present invention provides an acid-doped polyaniline, a method for preparing the same, and an anti-corrosion coating. The acid-doped polyaniline provided by the present invention can effectively improve the anti-corrosion effect and adhesion of the anti-corrosion coating.

[0008] This invention provides a method for preparing acid-doped polyaniline, comprising the following steps:

[0009] Polyaniline reacts with organic acid in a solvent medium, then the solid and liquid are separated, the resulting solid product is washed and dried to obtain acid-doped polyaniline;

[0010] in,

[0011] The organic acid is hydroxyethylidene diphosphate.

[0012] Preferably, the molar ratio of the organic acid to the phenylenediamine unit in the polyaniline is (0.3-2.5):1.

[0013] Preferably, the molar ratio of the organic acid to the phenylenediamine unit in the polyaniline is 1.5:1.

[0014] Preferably, the reaction temperature is 10–60°C and the reaction time is 0.5–24 h.

[0015] Preferably, the reaction is carried out at a temperature of 30°C for 6 hours.

[0016] Preferably, the polyaniline, organic acid, and solvent medium are brought into contact in any of the following ways (1) to (3):

[0017] Method (1): Add polyaniline and organic acid solution to a container respectively, and then add solvent to dilute;

[0018] Method (2): Add polyaniline and diluted organic acid solution to a container and mix them separately;

[0019] Method (3): Polyaniline, organic acid, and solvent are added to a container and mixed separately;

[0020] In the method (1): the mass fraction of the organic acid solution is 55% to 65%; the ratio of the amount of solvent added to the amount of polyaniline used when adding solvent for dilution is (10 to 20) mL: 1g.

[0021] Preferably, the solvent is water;

[0022] The degree of washing is such that the pH of the washing solution is 4.5 to 6 after washing;

[0023] The drying process is freeze-drying.

[0024] The present invention also provides an acid-doped polyaniline, which is prepared by the preparation method described in the above technical solution.

[0025] The present invention also provides an anti-corrosion coating, wherein the polyaniline is the acid-doped polyaniline described in the above technical solution.

[0026] Preferred ingredients include polyaniline and epoxy resin.

[0027] Acid doping of polyaniline significantly improves its performance by increasing the doping degree. However, existing technologies often involve excessive amounts of doping acid, prolonged doping times, and excessively high doping temperatures, resulting in wasted resources and time, poor doping effects, and low doping degrees, preventing the maximum reduction in particle size. The preparation method provided by this invention involves reacting polyaniline with a specific organic acid in a solvent medium, followed by solid-liquid separation, washing and drying of the resulting solid product to obtain acid-doped polyaniline. This method can be completed under mild conditions, and the doped polyaniline obtained by this invention effectively improves the doping effect, resulting in high doping degree and small particle size. Furthermore, the method of this invention can be completed under mild conditions, requires low acid dosage, and has a short reaction time, thus saving costs.

[0028] Experimental results show that the diameter of a single particle in the acid-doped polyaniline product obtained by this invention is reduced to below 3 μm, and the doping degree reaches more than 14%; under preferred conditions, the diameter of a single particle in the product is reduced to below 1.5 μm, and the doping degree reaches more than 20%. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a SEM image of intrinsic polyaniline;

[0031] Figure 2 This is a SEM image of the doped polyaniline obtained in Example 8 of the present invention;

[0032] Figure 3 XPS plot of intrinsic polyaniline;

[0033] Figure 4 This is an XPS image of the doped polyaniline obtained in Example 8 of the present invention. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0036] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0037] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0038] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 10~60℃ means that the units for the left endpoint "10" and the right endpoint "60" are both in℃.

[0039] A method for preparing acid-doped polyaniline includes the following steps:

[0040] Polyaniline reacts with organic acid in a solvent medium, then the solid and liquid are separated, the resulting solid product is washed and dried to obtain acid-doped polyaniline;

[0041] in,

[0042] The organic acid is hydroxyethylidene diphosphate.

[0043] In this invention, the polyaniline is preferably intrinsic polyaniline. The particle size of the intrinsic polyaniline is preferably 4–6 μm, more preferably 5 μm. The polyaniline is preferably intermediate polyaniline, i.e., the molar ratio of phenylenediamine units to quinone diimide units in the repeating unit is 3:1. This invention does not impose any particular limitation on the source of the intrinsic polyaniline; it can be a commercially available product or prepared according to methods known in the art.

[0044] In this invention, the organic acid is hydroxyethylidene diphosphonic acid. Using this specific organic acid to dope polyaniline provides excellent corrosion protection for various metals such as steel, iron, aluminum, and copper.

[0045] In this invention, the molar ratio of the organic acid to the phenylenediamine unit in polyaniline is preferably (0.3-2.5):1, specifically 0.3:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, and more preferably 1.5:1 or 2.5:1.

[0046] In this invention, the solvent is preferably water. The water is preferably deionized water.

[0047] In this invention, the preferred method for contacting the polyaniline, organic acid, and solvent medium is any one of the following methods (1) to (3):

[0048] Method (1): Add polyaniline and organic acid solution to a container respectively, and then add solvent to dilute;

[0049] Method (2): Add polyaniline and diluted organic acid solution to a container and mix them separately;

[0050] Method (3): Add polyaniline, organic acid and solvent to a container and mix them separately.

[0051] Regarding method (1): the organic acid solution is a solution formed by dissolving an organic acid in a solvent; wherein, the range of solvent selection is consistent with the range of solvent types described in the previous technical solution, and will not be repeated here. The mass fraction of the organic acid solution is preferably 55% to 65%, specifically 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, and more preferably 60%. The range of solvent selection used for dilution is consistent with the range of solvent types described in the previous technical solution, and will not be repeated here. Preferably, it is consistent with the solvent in the organic acid solution (for example, when the solvent in the organic acid solution is water, dilution is also performed using water). When diluting with solvent, the ratio of the amount of solvent added to the amount of polyaniline is preferably (10-20) mL:1g, specifically 10mL:1g, 11mL:1g, 12mL:1g, 13mL:1g, 14mL:1g, 15mL:1g, 16mL:1g, 17mL:1g, 18mL:1g, 19mL:1g, or 20mL:1g.

[0052] Regarding method (2): The main difference between method (2) and method (1) is that the organic acid solution is prepared by diluting the organic acid solution with a solvent in advance, and then the polyaniline and the diluted organic acid solution are directly added to the container for mixing; that is, the "adding solvent to dilute" step in method (1) is moved forward, while the types of materials and the overall usage remain unchanged, which will not be elaborated here.

[0053] Regarding method (3): The main difference between method (3) and method (1) is that instead of using a solvent to dissolve the organic acid, polyaniline, organic acid, and solvent are directly added to the container for mixing. The types of materials and the overall amount of each material are the same as in method (1), and will not be repeated here.

[0054] In addition to the methods (1) to (3) above, other material contact methods that are only formally modified but essentially the same also fall within the scope of protection of this invention. In this invention, the most preferred method is (1).

[0055] In this invention, the reaction temperature is preferably 10–60°C, specifically 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, and more preferably 30°C. The reaction time is preferably 0.5–24 h, specifically 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 12 h, 24 h, and more preferably 6 h. The reaction is preferably a isothermal reaction. More preferably, the reaction is an isothermal stirring reaction, i.e., the reaction is accompanied by stirring; wherein the stirring rate is preferably 400–1000 rpm, specifically 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, and 1000 rpm.

[0056] Acid doping of polyaniline significantly improves its performance by increasing the doping degree. In this invention, the optimal reaction conditions are: a molar ratio of organic acid to phenylenediamine units in polyaniline of 1.5:1 or 2.5:1, a reaction temperature of 30°C, and a reaction time of 6 hours. Under these optimal acid ratio, reaction temperature, and time, the highest doping degree can be achieved, resulting in doped polyaniline with a particle size reduced to approximately 1.5 μm.

[0057] In this invention, solid-liquid separation is performed after the above reaction. This invention does not impose any particular limitation on the method of solid-liquid separation; any conventional solid-liquid separation method in the art is acceptable, with filtration being preferred. The filtration is preferably vacuum filtration.

[0058] In this invention, after solid-liquid separation, the obtained solid product is washed. Preferably, the washing is done with water, preferably distilled water. The degree of washing is preferably until the pH of the washing liquid is 4.5–6, specifically 4.5, 5.0, 5.5, or 6.0; the washing liquid refers to the washing liquid discharged after washing. In this invention, after washing, it is preferable to further remove the washing liquid by vacuum filtration.

[0059] In this invention, after the above washing, the obtained solid product is dried. For vacuum filtration, the solid product is the filter cake after filtration. In this invention, the drying is preferably freeze-drying. After the above drying, acid-doped polyaniline is obtained. In this invention, the particle size of the obtained acid-doped polyaniline is below 2 μm. The particle size of the original intrinsic state polyaniline is about 5 μm. After doping with the specific organic acid of this invention, the particle size of polyaniline can be effectively reduced to below 2 μm, and under optimal doping conditions, it can be reduced to about 1.5 μm.

[0060] This invention also provides an acid-doped polyaniline, prepared by the method described in the above technical solution. In this invention, the particle size of the acid-doped polyaniline is below 2 μm, and can be reduced to approximately 1.5 μm under optimal doping conditions.

[0061] The present invention also provides an anti-corrosion coating, wherein the polyaniline is the acid-doped polyaniline described in the above technical solution.

[0062] In this invention, the anti-corrosion coating preferably comprises acid-doped polyaniline and epoxy resin. The type of epoxy resin is not particularly limited; any conventional epoxy resin used in anti-corrosion coatings is acceptable. In this invention, the amount of acid-doped polyaniline is 0.5% to 2% of the mass of the epoxy resin. This low addition amount achieves excellent anti-corrosion effects and reduces costs. In this invention, the preparation method of the anti-corrosion coating is not particularly limited; any conventional preparation method in the art is acceptable, such as blending acid-doped polyaniline and epoxy resin.

[0063] Acid doping of polyaniline significantly improves its performance by increasing the doping degree. However, existing technologies often involve excessive amounts of doping acid, prolonged doping times, and excessively high doping temperatures, resulting in wasted resources and time, poor doping effects, and low doping degrees, preventing the maximum reduction in particle size. The preparation method provided by this invention involves reacting polyaniline with a specific organic acid in a solvent medium, followed by solid-liquid separation, washing and drying of the resulting solid product to obtain acid-doped polyaniline. This method can be completed under mild conditions, and the doped polyaniline obtained by this invention effectively improves the doping effect, resulting in high doping degree and small particle size. Furthermore, the method of this invention can be completed under mild conditions, requires low acid dosage, and has a short reaction time, thus saving costs.

[0064] The acid-doped polyaniline obtained by this invention exhibits high dispersion when mixed with resin in anti-corrosion coatings, resulting in good anti-corrosion effect and adhesion. Furthermore, the acid-doped polyaniline obtained by this invention requires a low addition amount, thus reducing the amount of acid-doped polyaniline used, thereby lowering production costs and expanding its application range. In addition, the preparation method of this invention is simple and has low preparation cost.

[0065] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0066] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. The intrinsic polyaniline has a particle size of approximately 5 μm and was synthesized using the solution polymerization method described in the article "Research Progress on the Synthesis and Polymerization Mechanism of Polyaniline". The obtained polyaniline product was continuously stirred in a 0.5 mol / L ammonia solution for 24 h, filtered through a G4 sintered glass funnel, and washed with a large amount of deionized water until the filtrate was neutral to obtain the intrinsic polyaniline. The epoxy resin was ordinary bisphenol A type epoxy resin E44, provided by Jiangsu Sanmu.

[0067] Example 1

[0068] Weigh 1g of intrinsic polyaniline and place it in a reactor. Add an aqueous solution of hydroxyethylidene diphosphoric acid (mass fraction 60%) to the reactor, wherein the molar ratio of hydroxyethylidene diphosphoric acid to the phenylenediamine unit in polyaniline is 2:1. Then add 15mL of deionized water for dilution. Then, stir the reaction at 50℃ for 0.5h (stirring rate 600rpm). After that, filter, wash the obtained solid product with distilled water to make the pH of the filtrate 5, filter under reduced pressure, freeze-dry the filter cake to obtain doped polyaniline.

[0069] Example 2

[0070] The procedure was carried out as in Example 1, except that the reaction time was adjusted to 12 hours.

[0071] Example 3

[0072] The procedure was carried out as in Example 1, except that the reaction time was adjusted to 24 hours.

[0073] Example 4

[0074] Weigh 1g of intrinsic polyaniline and place it in a reactor. Add an aqueous solution of hydroxyethylidene diphosphoric acid (mass fraction 60%) to the reactor, wherein the molar ratio of hydroxyethylidene diphosphoric acid to the phenylenediamine unit in polyaniline is 2:1. Then add 15mL of deionized water for dilution. Then, stir the reaction at 10°C for 6h (stirring rate is the same as in Example 1). After that, filter the product and wash the obtained solid product with distilled water to make the pH of the filtrate 5. Filter under reduced pressure and freeze-dry the filter cake to obtain doped polyaniline.

[0075] Example 5

[0076] The experiment was carried out according to Example 4, except that the reaction temperature was adjusted to 60°C.

[0077] Example 6

[0078] Weigh 1g of intrinsic polyaniline and place it in a reactor. Add an aqueous solution of hydroxyethylidene diphosphoric acid (mass fraction 60%) to the reactor, wherein the molar ratio of hydroxyethylidene diphosphoric acid to the phenylenediamine unit in polyaniline is 0.3:1. Then add 15mL of deionized water for dilution. Then, stir the reaction at 30°C for 6h (stirring rate is the same as in Example 1). After that, filter the product and wash the obtained solid product with distilled water to make the pH of the filtrate 5. Filter under reduced pressure and freeze-dry the filter cake to obtain doped polyaniline.

[0079] Example 7

[0080] The method was implemented according to Example 6, except that the molar ratio of hydroxyethylidene diphosphate to the phenylenediamine unit in polyaniline was 2.5:1.

[0081] Example 8

[0082] The method was implemented according to Example 6, except that the molar ratio of hydroxyethylidene diphosphate to the phenylenediamine unit in polyaniline was 1.5:1.

[0083] Product Testing :

[0084] (1) Scanning electron microscopy (SEM) characterization

[0085] SEM images of intrinsic polyaniline and doped polyaniline obtained in Example 8 are shown below. Figure 1-2 As shown, it can be seen that the particle size of the doped polyaniline obtained in Example 8 is significantly reduced compared to the intrinsic state. Figure 2 The diameter of individual particles in the medium-sized aggregates has been reduced to below 1.5 μm.

[0086] (2) X-ray photoelectron spectroscopy (XPS) analysis

[0087] The XPS plots of the intrinsic polyaniline and the doped polyaniline obtained in Example 8 are shown below. Figure 3-4 As shown, Figure 3 The peak at 399.68 eV in the intrinsic state XPS spectrum represents an aniline unit, and the peak at 398.83 eV represents a quinone imine unit. The ratio of their peak areas is approximately 1:1, proving that the intrinsic state polyaniline is undoped. Figure 4 The peak at 401.28 eV represents the protonated imine unit, and the peak at 399.31 eV represents the aniline unit. The ratio of the peak area at the protonated imine unit to the total peak area represents the doping degree, which is 20.63%.

[0088] The doped polyaniline of Examples 1-8 and Comparative Example 1 were subjected to the above tests, and the results are shown in Table 1.

[0089] Table 1: Test Results of Products Obtained from Each Example and Comparative Example

[0090] Individual particle diameter in the product Doping Example 1 2-3μm 14.53％ Example 2 1-2μm 18.03％ Example 3 0.8-2μm 19.35％ Example 4 0.8-2μm 19.35％ Example 5 0.8-1.8μm 20.03％ Example 6 1-2μm 17.36％ Example 7 0.6-1.5μm 21.26％ Example 8 Below 1.5μm 20.63％

[0091] As can be seen from the test results in Table 1, Examples 1-8 of the present invention have good doping levels and reduced polyaniline particle size. Among them, Examples 7-8 have the best overall effect.

[0092] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing acid-doped polyaniline, characterized in that, Includes the following steps: Polyaniline reacts with organic acid in a solvent medium, then the solid and liquid are separated, the resulting solid product is washed and dried to obtain acid-doped polyaniline; in, The organic acid is hydroxyethylidene diphosphate; The molar ratio of the organic acid to the phenylenediamine unit in the polyaniline is 1.5:1 or 2.5:1; The reaction was carried out at a temperature of 30°C for 6 hours.

2. The preparation method according to claim 1, characterized in that, The polyaniline, organic acid, and solvent medium are brought into contact in any of the following ways (1) to (3): Method (1): Add polyaniline and organic acid solution to a container respectively, and then add solvent to dilute; Method (2): Add polyaniline and diluted organic acid solution to a container and mix them separately; Method (3): Polyaniline, organic acid, and solvent are added to a container and mixed separately; In the method (1): the mass fraction of the organic acid solution is 55%~65%; the ratio of the amount of solvent added to the amount of polyaniline used when adding solvent for dilution is (10~20) mL: 1g.

3. The preparation method according to claim 1, characterized in that, The solvent is water; The degree of washing is such that the pH of the washing solution is 4.5-6 after washing; The drying process is freeze-drying.

4. An acid-doped polyaniline, characterized in that, It is prepared by any one of claims 1 to 3.

5. An anti-corrosion coating, characterized in that, The polyaniline therein is the acid-doped polyaniline as described in claim 4.

6. The anti-corrosion coating according to claim 5, characterized in that, include: Polyaniline and epoxy resin.

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