Corrosion-resistant coating and preparation method thereof

Abstract

The invention provides a corrosion-resistant coating and a preparation method thereof, and belongs to the technical field of coatings. Comprising the following components: 8 to 10 parts of polyaniline aqueous dispersion liquid, 21 to 25 parts of aqueous fluorocarbon resin, 25 to 30 parts of epoxy resin, 18 to 22 parts of butyl acetate, 16 to 17 parts of expandable graphite powder, 0.5 to 0.8 part of a silane coupling agent, 90 to 100 parts of deionized water, 2.0 to 2.3 parts of sodium stearate modified graphene and 2.5 to 2.7 parts of fluorine modified polyacrylamide. According to the invention, the impact resistance of the prepared corrosion-resistant coating can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and particularly relates to a corrosion-resistant coating and a preparation method thereof. Background Art

[0002] Metal corrosion is a common phenomenon that reduces the service life of materials and can even cause safety accidents in severe cases. Research on metal corrosion protection has great application value, and applying organic coatings on metal surfaces is a simple and effective anti-corrosion method. Currently, the anti-corrosion coatings available on the market are mainly solvent-based coating systems. From the perspective of energy saving and environmental protection, water-based coatings have been a hot topic in the research field in recent years. In the existing technology, polyaniline aqueous dispersions have unique redox properties and are used to prepare anti-corrosion coatings with a new anti-corrosion mechanism. A good anti-corrosion effect can be achieved using a relatively small amount of polyaniline aqueous dispersion, which is cost-effective.

[0003] In addition, in order to improve the fire resistance / flame retardancy of the coating, expandable graphite powder is added to the anti-corrosion coating. Expandable graphite powder is a filler with flame retardant and heat-insulating functions. When exposed to high temperatures, it expands to form a dense carbon layer, which blocks heat, effectively prevents fire, and enhances the coating's anti-leakage properties.

[0004] However, the worm-like carbon layers of expandable graphite powder (the interlayer spacing increases 80-300 times after expansion) can disrupt the resin continuity, resulting in a decrease in the coating's impact strength and impact resistance. Therefore, improving the impact strength of this fire-retardant and anti-corrosion coating is a worthy research question. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a corrosion-resistant coating and a preparation method thereof, which can effectively improve the impact strength / impact resistance of the finally obtained corrosion-resistant coating with fireproof / flame retardant properties.

[0006] In order to achieve the above-mentioned objectives, in a first aspect, the present invention provides a corrosion-resistant coating, comprising the following components, by weight: 8-10 parts of polyaniline aqueous dispersion, 21-25 parts of aqueous fluorocarbon resin, 25-30 parts of epoxy resin, 18-22 parts of butyl acetate, 16-17 parts of expandable graphite powder, 0.5-0.8 parts of silane coupling agent, 90-100 parts of deionized water, 2.0-2.3 parts of sodium stearate modified graphene and 2.5-2.7 parts of fluorine-modified polyacrylamide.

[0007] Furthermore, the preparation method of the stearic acid-modified graphene is as follows: A1. Add 100-120 mL of distilled water to 0.1-0.15 g of graphene oxide, disperse ultrasonically, add 5-6 mg of stearic acid, adjust the pH to 7-8, react at 70±2° C. for 2-2.5 h, add 1.0 mL of hydrazine hydrate, and heat the mixture at 100±2° C. for 24 h to obtain a reaction mixture; A2. The reaction mixture obtained in A1 is filtered through a semipermeable membrane, and washed alternately with distilled water, methanol, and anhydrous ethanol for multiple times, and dried to obtain stearic acid-modified graphene.

[0008] Furthermore, in A1, the frequency of ultrasonic dispersion is 50-60 KHz, and the time of ultrasonic dispersion is 30-35 min.

[0009] Furthermore, in A2, the drying temperature is 75-85° C., and the drying time is 5-7 h.

[0010] Furthermore, the preparation method of the fluorine-modified polyacrylamide is as follows: B1. Place hexadecyltrimethylammonium bromide, perfluorooctylethyl acrylate, and deionized water in a three-necked flask, place the flask in a constant temperature water bath at 50°C, and stir to dissolve. Then, add acrylamide and diallyldimethylammonium chloride, adjust the mixture to neutrality with 30% ammonia water, and then add an initiator to obtain a reaction solution. B2. The reaction solution obtained in B1 was subjected to a constant temperature polymerization reaction at 50°C for 8 hours to obtain a polymer and discharge the polymer. The polymer was dried and crushed, and then extracted and purified with acetone-ethanol for 12 hours, and then vacuum dried at 40-45°C for 50-60 minutes to obtain fluorine-modified polyacrylamide.

[0011] Furthermore, in the reaction solution, the mass fraction of hexadecyltrimethylammonium bromide is 1.3-1.5%, the mass fraction of perfluorooctylethyl acrylate is 0.25%-0.35%, the mass fraction of acrylamide is 81-83%, the mass fraction of diallyldimethylammonium chloride is 14-16%, and the mass fraction of the initiator is 0.2%-0.4%.

[0012] Furthermore, the initiator includes sodium bisulfite and potassium persulfate, and the molar ratio of the sodium bisulfite to potassium persulfate is 1:2.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned corrosion-resistant coating, comprising the following steps: S1. Adding polyaniline aqueous dispersion and aqueous fluorocarbon resin to deionized water, stirring at 65-68° C. for 100-110 minutes to obtain a mixture; S2. Add epoxy resin, butyl acetate, expandable graphite powder, silane coupling agent, stearic acid-modified graphene and fluorine-modified polyacrylamide to the mixture obtained in S1, ultrasonically disperse at 56-58° C., and cool in a water bath at 12-15° C. for 100-110 minutes to obtain the corrosion-resistant coating.

[0014] Furthermore, in S2, the frequency of ultrasonic dispersion is 80-90 kHz, and the time of ultrasonic dispersion is 130-140 min.

[0015] This application has the following beneficial effects: 1. The fluorinated chain segments of the fluorine-modified polyacrylamide of the present invention have a strong affinity with water-based fluorocarbon resins. At the same time, its amide group (-CONH2) adsorbs graphene sheets through hydrogen bonds, forming a "rigid sheet-flexible chain-matrix" transition interface, improving dispersibility and reducing stress concentration. The high molecular weight long chains of the fluorine-modified polyacrylamide absorb impact energy through reversible stretching and viscoelastic deformation when subjected to force. The fluorine-containing groups also enhance the slip ability of the molecular chains, improve energy dissipation efficiency, and thus improve the impact strength and impact resistance of the coating.

[0016] 2. Graphene sheets and long chains of polyacrylamide are interwoven with each other to form a "rigid-flexible" composite structure, which not only maintains shielding properties but also improves toughness; the fluorine-containing groups react with fluorocarbon resins to enhance interfacial bonding, and the hydrophobicity of stearic acid and the water retention of polyacrylamide balance the internal stress of the coating; the porous structure of the expandable graphite powder provides a carrier for fluorine-modified polyacrylamide and stearic acid-modified graphene, and the three together form an interpenetrating network. The impact energy is dissipated through multiple levels of graphene dispersion, polyacrylamide deformation and pore buffering, thereby synergistically improving the impact strength / impact resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , a comparative trend chart of impact resistance test data of the corrosion-resistant coatings prepared in Examples 1 to 4 and Comparative Examples 1 to 4 in the test examples of the present invention; Figure 2 , a comparative trend chart of the corrosion area test data of the corrosion-resistant coatings prepared in Examples 1 to 4 and Comparative Examples 1 to 4 in the test examples of the present invention. DETAILED DESCRIPTION

[0018] The present application is further described in detail below with reference to the embodiments.

[0019] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0020] Example 1: (1) Preparation of stearic acid-modified graphene, the preparation method is as follows: A1. To 0.12 g of graphene oxide, 110 mL of distilled water was added, and the mixture was ultrasonically dispersed at a frequency of 55 kHz for 32 min. Then, 5.5 mg of stearic acid was added, and the pH was adjusted to 7.5. The mixture was reacted at 70°C for 2.2 h. Then, 1.0 mL of hydrazine hydrate was added, and the mixture was heated at 100°C for 24 h to obtain a reaction mixture.

[0021] A2. The reaction mixture obtained in A1 was filtered through a semipermeable membrane, and washed alternately with distilled water, methanol, and anhydrous ethanol for a total of 9 times, and dried at 80° C. for 6 h to obtain stearic acid-modified graphene.

[0022] (2) Preparation of fluorine-modified polyacrylamide, the preparation method is as follows: B1. Place hexadecyltrimethylammonium bromide, perfluorooctylethyl acrylate, and deionized water in a three-necked flask, and place the flask in a constant temperature water bath at 50°C. Stir to dissolve them. Then, add acrylamide and diallyldimethylammonium chloride, adjust the mixture to neutrality with 30% ammonia water, and then add an initiator to obtain a reaction solution.

[0023] The mass fraction of the initiator is 0.3%, the mass fraction of hexadecyltrimethylammonium bromide is 1.4%, the mass fraction of perfluorooctylethyl acrylate is 0.3%, the mass fraction of acrylamide is 83%, the mass fraction of diallyldimethylammonium chloride is 15%, and the mass fraction of the initiator is 0.3%. The initiator includes sodium bisulfite and potassium persulfate, and the molar ratio of sodium bisulfite to potassium persulfate is 1:2.

[0024] B2. The reaction solution obtained in B1 was subjected to a constant temperature polymerization reaction at 50°C for 8 hours to obtain a polymer and discharge the polymer. The polymer was dried and crushed, and then extracted and purified with acetone-ethanol for 12 hours, and then vacuum dried at 42°C for 55 minutes to obtain fluorine-modified polyacrylamide.

[0025] (3) Preparation of corrosion-resistant coating, the preparation method is as follows: S1. Add 9 parts of polyaniline aqueous dispersion and 23 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0026] The polyaniline aqueous dispersion (MTA-15 composite corrosion inhibitor) is a nano-scale polyaniline aqueous liquid with an average particle size of 20 nm, purchased from Puyang Debel Chemical Co., Ltd. The water-based fluorocarbon resin (FEM-101A-2) with a content of ≥99.9% was purchased from Shandong Moore Chemical Co., Ltd.

[0027] S2. Add 28 parts of epoxy resin (bisphenol A type water-based epoxy resin), 20 parts of butyl acetate, 16.5 parts of expandable graphite powder, 0.6 parts of silane coupling agent (KH-550), 2.1 parts of stearic acid-modified graphene and 2.6 parts of fluorine-modified polyacrylamide to the mixture obtained in S1. After ultrasonic dispersion at a frequency of 85 kHz at 57°C for 135 minutes, cool in a water bath at 13°C for 105 minutes to obtain a corrosion-resistant coating.

[0028] Example 2: The difference between this example and Example 1 is that the corrosion-resistant coating is prepared by the following method: S1. Add 8 parts of polyaniline aqueous dispersion and 21 parts of aqueous fluorocarbon resin, by weight, to 90 parts of deionized water, and stir at 65° C. for 110 minutes to obtain a mixture.

[0029] S2. Add 25 parts of epoxy resin, 18 parts of butyl acetate, 16 parts of expandable graphite powder, 0.5 parts of silane coupling agent, 2.0 parts of stearic acid-modified graphene and 2.5 parts of fluorine-modified polyacrylamide to the mixture obtained in S1, and ultrasonically disperse at 56°C and a frequency of 80 kHz for 140 min. Then cool in a water bath at 12°C for 100 min to obtain a corrosion-resistant coating.

[0030] Example 3: The difference between this example and Example 1 is that the corrosion-resistant coating is prepared by the following method: S1. Add 10 parts of polyaniline aqueous dispersion and 25 parts of aqueous fluorocarbon resin to 100 parts of deionized water, and stir at 68° C. for 100 minutes to obtain a mixture.

[0031] S2. Add 30 parts of epoxy resin, 22 parts of butyl acetate, 17 parts of expandable graphite powder, 0.8 parts of silane coupling agent, 2.3 parts of stearic acid-modified graphene and 2.7 parts of fluorine-modified polyacrylamide to the mixture obtained in S1, and ultrasonically disperse at 58°C and a frequency of 90 kHz for 130 min. Then cool in a water bath at 15°C for 110 min to obtain a corrosion-resistant coating.

[0032] Example 4: The difference between this example and Example 1 is that the corrosion-resistant coating is prepared by the following method: S1. Add 9 parts of polyaniline aqueous dispersion and 22 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0033] S2. Add 30 parts of epoxy resin, 22 parts of butyl acetate, 17 parts of expandable graphite powder, 0.7 parts of silane coupling agent, 2.3 parts of stearic acid-modified graphene and 2.7 parts of fluorine-modified polyacrylamide to the mixture obtained in S1. Ultrasonic dispersion is carried out at 57°C and a frequency of 85 kHz for 135 minutes. The mixture is then cooled in a water bath at 13°C for 105 minutes to obtain a corrosion-resistant coating.

[0034] Comparative Example 1: The difference between this comparative example and Example 1 is that in the preparation of the corrosion-resistant coating, stearic acid-modified graphene and fluorine-modified polyacrylamide are not added.

[0035] Specifically, the corrosion-resistant coating is prepared, and the preparation method thereof is as follows: S1. Add 9 parts of polyaniline aqueous dispersion and 23 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0036] S2. Add 28 parts of epoxy resin, 20 parts of butyl acetate, 16.5 parts of expandable graphite powder and 0.6 parts of silane coupling agent to the mixture obtained in S1. Ultrasonic dispersion is carried out at 57°C and a frequency of 85 kHz for 135 minutes. The mixture is then cooled in a water bath at 13°C for 105 minutes to obtain a corrosion-resistant coating.

[0037] Comparative Example 2: The difference between this comparative example and Example 1 is that no fluorine-modified polyacrylamide is added in the preparation of the corrosion-resistant coating.

[0038] Specifically, the corrosion-resistant coating is prepared, and the preparation method thereof is as follows: S1. Add 9 parts of polyaniline aqueous dispersion and 23 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0039] S2. Add 28 parts of epoxy resin, 20 parts of butyl acetate, 16.5 parts of expandable graphite powder, 0.6 parts of silane coupling agent and 2.1 parts of stearic acid-modified graphene to the mixture obtained in S1. Ultrasonic dispersion is carried out at 57°C and a frequency of 85 kHz for 135 minutes. The mixture is then cooled in a water bath at 13°C for 105 minutes to obtain a corrosion-resistant coating.

[0040] Comparative Example 3: The difference between this comparative example and Example 1 is that stearic acid-modified graphene is not added in the preparation of the corrosion-resistant coating.

[0041] Specifically, the corrosion-resistant coating is prepared, and the preparation method thereof is as follows: S1. Add 9 parts of polyaniline aqueous dispersion and 23 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0042] S2. Add 28 parts of epoxy resin, 20 parts of butyl acetate, 16.5 parts of expandable graphite powder, 0.6 parts of silane coupling agent and 2.6 parts of fluorine-modified polyacrylamide to the mixture obtained in S1, and perform ultrasonic dispersion at 57°C and a frequency of 85 kHz for 135 minutes. Then cool in a water bath at 13°C for 105 minutes to obtain a corrosion-resistant coating.

[0043] Comparative Example 4: The difference between this comparative example and Example 1 is that no polyaniline aqueous dispersion is added in the preparation of the corrosion-resistant coating.

[0044] Specifically, the corrosion-resistant coating is prepared, and the preparation method thereof is as follows: S1. Add 23 parts of aqueous fluorocarbon resin, by weight, to 95 parts of deionized water, and stir at 66° C. for 105 minutes to obtain a mixture.

[0045] S2. Add 28 parts of epoxy resin, 20 parts of butyl acetate, 16.5 parts of expandable graphite powder, 0.6 parts of silane coupling agent, 2.1 parts of stearic acid-modified graphene and 2.6 parts of fluorine-modified polyacrylamide to the mixture obtained in S1. Ultrasonic dispersion is carried out at 57°C and a frequency of 85 kHz for 135 min. The mixture is then cooled in a water bath at 13°C for 105 min to obtain a corrosion-resistant coating.

[0046] Test example: Test object: Corrosion-resistant coatings were prepared using Examples 1 to 4 and Comparative Examples 1 to 3. Test items and methods: ① Impact resistance of paint film (impact strength): Referring to GB / T 1732-2020 "Determination of impact resistance of paint film", a paint film test plate was made and tested using a 100cm elevated paint film impactor. The maximum drop height at which the heavy hammer does not cause damage to the paint film was recorded. The larger the value, the higher the impact strength / impact resistance of the corresponding paint film. ② Corrosion resistance: The paint film test plate was immersed in a 6% NaCl solution for three months, and the corrosion area value was observed and measured and recorded. The smaller the value, the higher the corrosion resistance of the corresponding paint film. Test results: See Table 1.

[0047] Table 1. Test example data

[0048] Result analysis: Analyze Example 1-Example 4 and combine the data in Table 1 and Figure 1-Figure 2 It can be seen that the corrosion-resistant coatings prepared in the present invention (Example 1-Example 4) have excellent paint film impact resistance and corrosion resistance.

[0049] Analyze Example 1 and Comparative Examples 1-4 and combine the data in Table 1 and Figure 1-Figure 2Specifically, by comparing Comparative Example 1 and Comparative Example 2, it can be seen that compared with Comparative Example 1, the addition of stearic acid-modified graphene to the raw material components of Comparative Example 2 results in a decrease in the impact resistance of the paint film of the corrosion-resistant coating. This is mainly because the rigid lamellae of stearic acid-modified graphene differ significantly from the modulus of the resin matrix, resulting in stress concentration and microcrack propagation, resulting in a decrease in impact strength. In addition, the hydrophobic long chain of stearic acid has poor compatibility with the water-based resin, exacerbating graphene agglomeration and weakening interfacial bonding, resulting in a further decrease in the impact strength of the coating.

[0050] Specifically, by comparing Comparative Examples 1 and 3, it can be seen that compared with Comparative Example 1, the addition of fluorine-modified polyacrylamide to the raw material components of Comparative Example 3 results in improved impact resistance of the paint film of the corrosion-resistant coating. Furthermore, by comparing with Example 1, it can be seen that the addition of fluorine-modified polyacrylamide and stearic acid-modified graphene to the raw material components can produce a synergistic effect, synergistically improving the impact resistance of the paint film of the corrosion-resistant coating.

[0051] Specifically, by comparing Comparative Example 4 with Example 1, it can be seen that compared with Comparative Example 4, the corrosion resistance of the paint film of the corrosion-resistant coating obtained by adding polyaniline aqueous dispersion to the raw material components of Example 1 is significantly improved.

[0052] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0053] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A corrosion-resistant coating, characterized in that: The invention comprises the following components in parts by weight: 8-10 parts of polyaniline aqueous dispersion, 21-25 parts of aqueous fluorocarbon resin, 25-30 parts of epoxy resin, 18-22 parts of butyl acetate, 16-17 parts of expandable graphite powder, 0.5-0.8 parts of silane coupling agent, 90-100 parts of deionized water, 2.0-2.3 parts of sodium stearate modified graphene and 2.5-2.7 parts of fluorine-modified polyacrylamide.

2. The corrosion-resistant coating according to claim 1, characterized in that: The preparation method of the stearic acid modified graphene is as follows: A1. Add 100-120 mL of distilled water to 0.1-0.15 g of graphene oxide, disperse ultrasonically, add 5-6 mg of stearic acid, adjust the pH to 7-8, react at 70±2° C. for 2-2.5 h, add 1.0 mL of hydrazine hydrate, and heat the mixture at 100±2° C. for 24 h to obtain a reaction mixture; A2. The reaction mixture obtained in A1 is filtered through a semipermeable membrane, and washed alternately with distilled water, methanol, and anhydrous ethanol for multiple times, and dried to obtain stearic acid-modified graphene.

3. The corrosion-resistant coating according to claim 2, characterized in that: In A1, the frequency of ultrasonic dispersion is 50-60 KHz, and the time of ultrasonic dispersion is 30-35 min.

4. The corrosion-resistant coating according to claim 2, characterized in that: In A2, the drying temperature is 75-85°C and the drying time is 5-7h.

5. The corrosion-resistant coating according to claim 1, characterized in that: The preparation method of the fluorine-modified polyacrylamide is as follows: B1. Place hexadecyltrimethylammonium bromide, perfluorooctylethyl acrylate, and deionized water in a three-necked flask, place the flask in a constant temperature water bath at 50°C, and stir to dissolve. Then, add acrylamide and diallyldimethylammonium chloride, adjust the mixture to neutrality with 30% ammonia water, and then add an initiator to obtain a reaction solution. B2. The reaction solution obtained in B1 was subjected to a constant temperature polymerization reaction at 50°C for 8 hours to obtain a polymer and discharge the polymer. The polymer was dried and crushed, and then extracted and purified with acetone-ethanol for 12 hours, and then vacuum dried at 40-45°C for 50-60 minutes to obtain fluorine-modified polyacrylamide.

6. The corrosion-resistant coating according to claim 5, characterized in that: In the reaction solution, the mass fraction of hexadecyltrimethylammonium bromide is 1.3-1.5%, the mass fraction of perfluorooctylethyl acrylate is 0.25-0.35%, the mass fraction of acrylamide is 81-83%, the mass fraction of diallyldimethylammonium chloride is 14-16%, and the mass fraction of the initiator is 0.2-0.4%.

7. The corrosion-resistant coating according to claim 5 or 6, characterized in that: The initiator includes sodium bisulfite and potassium persulfate, and the molar ratio of the sodium bisulfite to the potassium persulfate is 1:

2.

8. A method for preparing the corrosion-resistant coating according to any one of claims 1 to 7, characterized in that: The steps include: S1. Adding polyaniline aqueous dispersion and aqueous fluorocarbon resin to deionized water, stirring at 65-68° C. for 100-110 minutes to obtain a mixture; S2. Add epoxy resin, butyl acetate, expandable graphite powder, silane coupling agent, stearic acid-modified graphene and fluorine-modified polyacrylamide to the mixture obtained in S1, ultrasonically disperse at 56-58° C., and cool in a water bath at 12-15° C. for 100-110 minutes to obtain the corrosion-resistant coating.

9. The method for preparing the corrosion-resistant coating according to claim 8, characterized in that: In S2, the frequency of ultrasonic dispersion is 80-90 kHz, and the time of ultrasonic dispersion is 130-140 min.

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