Corrosion resistant coating and its use in aluminium alloy heat exchanger tubes

Abstract

The application relates to the field of corrosion-resistant coatings and discloses a corrosion-resistant coating and application of the corrosion-resistant coating in aluminum alloy heat exchange pipes, the corrosion-resistant coating comprising: a water-based epoxy resin, modified silicon dioxide nanotubes, modified composite fillers and an additive; the modified silicon dioxide nanotubes are prepared by reacting with an aminating modifier after 4-isocyanobenzoyl chloride is used to acylate the silicon dioxide nanotubes; the aminating modifier is synthesized by using pentaerythritol and phosphorus oxychloride to prepare a spirocyclic phosphate diacyl chloride, and then using 2-aminobenzimidazole and 3,5-diamino-1,2,4-triazole to substitute the spirocyclic phosphate diacyl chloride; the modified composite fillers are prepared by using dopamine to self-polymerize on the outer surface of mica to form a polydopamine layer, then using a sol-gel method and high-temperature calcination to wrap zinc oxide on the outer layer of the dopamine-modified mica, and then using KH550 modification, the coating prepared by the application has good mechanical properties, corrosion resistance, heat insulation, flame retardation and antibacterial effects.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant coating technology, specifically relating to a corrosion-resistant coating and its application in aluminum alloy heat exchange tubes. Background Technology

[0002] Aluminum alloys have good corrosion resistance, but they are prone to pitting corrosion in marine salt spray environments, such as aluminum alloy heat exchange tubes. A heat exchange tube coating is a protective layer applied to the surface of the heat exchange tube to improve its corrosion resistance and mechanical properties. The coating prevents direct contact between the metal surface and the medium, thereby reducing corrosion and wear.

[0003] Epoxy resin coatings possess excellent mechanical, thermal, and anti-corrosion properties, making them widely used in corrosion-resistant coatings. However, they also exhibit some shortcomings. For instance, during the curing process, solvent evaporation can create micropores and defects, allowing corrosive media to gradually penetrate and cause corrosion over time. Therefore, inorganic nanofillers are often added to fill the epoxy resin to improve its performance. However, these inorganic nanofillers are often difficult to disperse in the base material, thus affecting mechanical properties. Furthermore, existing epoxy resin coatings have shortcomings in heat insulation, flame retardancy, and antibacterial properties, and their corrosion resistance needs further improvement. Current technologies enhance flame retardancy and antibacterial properties by adding inorganic flame retardants or antibacterial agents, but simple physical mixing easily leads to precipitation, making it difficult to guarantee the coating's long-lasting flame retardant or antibacterial effect. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a corrosion-resistant coating and its application in aluminum alloy heat exchange tubes. By adding modified silica nanotubes and modified composite fillers, the coating is endowed with good mechanical properties, corrosion resistance, heat insulation, flame retardancy, and antibacterial effects.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A corrosion-resistant coating comprises the following components in parts by weight: 45-70 parts of waterborne epoxy resin, 7-16 parts of modified silica nanotubes, 4-9 parts of modified composite filler, 5-12 parts of curing agent, 0.5-2.5 parts of wetting agent, 0.3-1 part of defoamer, 0.2-0.8 parts of leveling agent, and 0.1-0.6 parts of dispersant;

[0007] The modified silica nanotubes are prepared by chlorinating silica nanotubes with 4-isocyanobenzoyl chloride and then reacting them with an amylating modifier; the amylating modifier is prepared by synthesizing spirocyclic phosphate diacyl chloride using pentaerythritol and phosphorus oxychloride as raw materials, and then reacting 2-aminobenzimidazole and 3,5-diamino-1,2,4-triazole with the chlorine atoms at both ends of the spirocyclic phosphate diacyl chloride.

[0008] The silica nanotubes are prepared by reacting toluene-2,4-diisocyanate with hydroxylated carbon nanotubes to obtain isocyanate-based carbon nanotubes, which are then covalently grafted with polyethylene glycol to prepare modified carbon nanotubes. Subsequently, using the modified carbon nanotubes as templates and tetraethyl orthosilicate as raw material, the nanotubes are prepared by sol-gel method under alkaline conditions and after heat treatment to remove the template.

[0009] The modified composite filler is made by modifying the composite filler with silane coupling agent KH550; the composite filler is made by self-polymerizing dopamine on the outer surface of mica to form a polydopamine layer, and then coating the dopamine-modified mica with a layer of zinc oxide by sol-gel method and high temperature calcination.

[0010] Preferably, the method for preparing the modified silica nanotubes includes the following steps:

[0011] A. Take pentaerythritol, chlorobenzene, phosphorus oxychloride and 4-dimethylaminopyridine in a reactor, purge the reaction under nitrogen protection, and react at 60~70℃ for 2~3h. Then raise the temperature to 95~100℃ and continue the reaction for 6~8h. After the reaction is completed, stop heating and let stand for 8~10h. Filter the product, wash it with dichloromethane, and dry it under vacuum to prepare spirocyclic phosphate diacyl chloride.

[0012] B. Spirocyclic phosphate diacyl chloride and acetonitrile were placed in a reactor and heated to 50-60℃ under a nitrogen atmosphere. 2-aminobenzimidazole, 3,5-diamino-1,2,4-triazole and anhydrous methanol were stirred and mixed evenly, and then added to the reactor. The mixture was stirred and reacted at 65-75℃ for 6-8 hours. After the reaction was completed, the mixture was filtered, washed and dried to prepare the amination modifier.

[0013] C. Disperse silica nanotubes ultrasonically in acetone solvent, then add 4-isocyanobenzoyl chloride and dibutyltin dilaurate and stir to mix. Place the mixture at 40~60℃ and stir to react for 12~24h. After the reaction is completed, filter, wash and dry to prepare acyl chloride silica nanotubes.

[0014] D. Acyl chloride silica nanotubes were ultrasonically dispersed in tetrahydrofuran solvent, and then an amino modifier and pyridine were added and stirred. The mixture was placed at 25~40℃ and stirred for 6~18h. After the reaction was completed, the modified silica nanotubes were prepared by filtration, washing and drying.

[0015] Preferably, in step A, the molar ratio of pentaerythritol to phosphorus oxychloride is 1:2 to 2.5; and in step B, the molar ratio of spirocyclic phosphate diacyl chloride, 2-aminobenzimidazole, and 3,5-diamino-1,2,4-triazole is 1:1 to 1.1:1 to 1.1.

[0016] Preferably, the method for preparing silica nanotubes in step C includes the following steps:

[0017] C1. Hydroxylated carbon nanotubes were dispersed in toluene-2,4-diisocyanate and reacted at 75-85℃ for 70-72h under nitrogen protection. After the reaction was completed, the nanotubes were filtered, washed and dried to prepare isocyanate-based carbon nanotubes.

[0018] C2. Isocyanated carbon nanotubes, polyethylene glycol and toluene are placed in a reactor and ultrasonically dispersed at 55-70℃ for 20-30 min under nitrogen protection. Then, the mixture is reacted at 90-100℃ for 30-36 h. After the reaction is completed, the mixture is filtered, washed and dried to prepare modified carbon nanotubes.

[0019] C3. The modified carbon nanotubes were ultrasonically dispersed in an ethanol solution, and tetraethyl orthosilicate was added dropwise. The mixture was then ultrasonically dispersed for 20-30 minutes, followed by the addition of ammonia. The mixture was stirred and reacted at room temperature for 20-24 hours, and then allowed to stand for aging. After filtration, washing, and drying, the modified carbon nanotubes coated with silica were calcined in air at 480-520°C for 5-7 hours to prepare silica nanotubes.

[0020] Preferably, in step D, the mass ratio of acyl chloride silica nanotubes to aminated modifier is 1:0.5~1.

[0021] Preferably, the preparation method of the modified composite filler includes the following steps:

[0022] (1) Take tris(hydroxymethyl)aminomethane and deionized water in a reactor, adjust the pH to 8.5 with hydrochloric acid, then add the ground mica powder, disperse it evenly by ultrasonication, and then add dopamine hydrochloride while stirring. Stir the reaction at room temperature for 20-24 hours. After the reaction is completed, filter, wash and dry to prepare dopamine-modified mica.

[0023] (2) Dopamine-modified mica was ultrasonically dispersed in ethanol and deionized water, heated to 65-75℃, and zinc nitrate hexahydrate and polyethylene glycol dispersant were added. The mixture was stirred for 1-1.5 h, and then a mixed solution of ammonia and deionized water was added dropwise. After the addition was complete, the reaction was continued for 1.5-2 h. After the reaction was completed, the mixture was filtered, washed, dried, ground, and placed in a tube furnace. It was then calcined at 950-1000℃ for 2-2.5 h to prepare the composite filler.

[0024] (3) Take the composite filler and ultrasonically disperse it in a mixed solution of anhydrous ethanol and silane coupling agent KH550. Place it at 55~70℃ and stir for 3~5h. Then slowly add deionized water and stir for 2~3h. After the reaction is completed, filter, wash and dry to prepare the modified composite filler.

[0025] Preferably, in step (2), the mass ratio of dopamine-modified mica to zinc nitrate hexahydrate is 0.07~0.08:2.4; and the heating rate of the tube furnace is 8~10℃ / min.

[0026] Preferably, the curing agent is an amine curing agent; the wetting agent is polydimethylsiloxane; the defoamer is one of fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether; the leveling agent is sodium polyacrylate; and the dispersant is one of BYK-190 or BYK-191.

[0027] Preferably, the method for preparing the corrosion-resistant coating includes the following steps: weighing each raw material according to the weight parts, mixing the water-based epoxy resin and dispersant evenly, then adding modified silica nanotubes, modified composite fillers, wetting agents, and leveling agents and stirring evenly, then adding curing agents and defoamers and continuing to stir evenly to prepare the corrosion-resistant coating.

[0028] One application of the corrosion-resistant coating is to apply the corrosion-resistant coating to the surface of an aluminum alloy heat exchange tube by a coating method.

[0029] The beneficial effects of this invention are:

[0030] This invention utilizes pentaerythritol and phosphorus oxychloride as raw materials to synthesize spirocyclic phosphate diacyl chloride. Then, 2-aminobenzimidazole and 3,5-diamino-1,2,4-triazole are used to undergo substitution reactions with the chlorine atoms at both ends of the spirocyclic phosphate diacyl chloride to prepare an aminated modifier. Simultaneously, this invention utilizes 4-isocyanobenzoyl chloride to react with the hydroxyl groups on the surface of silica nanotubes to prepare acyl chloride silica nanotubes. Then, an amidation reaction is used to graft the aminated modifier onto the surface of the silica nanotubes, thereby introducing antibacterial benzimidazole groups, synergistic flame-retardant phosphorus and nitrogen elements onto the silica nanotube surface. This imparts excellent antibacterial and flame-retardant properties to the coating, and the strong chemical bonds facilitate long-term effects. Furthermore, the grafting reaction improves the surface oleophilicity of the silica nanotubes, allowing them to be relatively uniformly dispersed in the matrix material, thus avoiding performance defects caused by silica nanotube agglomeration.

[0031] In this invention, toluene-2,4-diisocyanate is reacted with hydroxylated carbon nanotubes to prepare isocyanate-based carbon nanotubes. Then, polyethylene glycol is covalently grafted onto the surface of the isocyanate-based carbon nanotubes to prepare modified carbon nanotubes with good dispersibility. Subsequently, using the modified carbon nanotubes as templates and tetraethyl orthosilicate as raw material, hollow silica nanotubes are prepared under alkaline conditions using a sol-gel method and after heat treatment to remove the template. These silica nanotubes possess good thermal stability, mechanical properties, and high-temperature resistance. Furthermore, their hollow structure can absorb stress, prevent crack propagation, improve the impact resistance of the coating, and also have good thermal insulation effects.

[0032] This invention utilizes the self-polymerizing property of dopamine to coat a layer of polydopamine onto the surface of mica, preparing dopamine-modified mica. Then, a zinc oxide shell is grown around the dopamine-modified mica using a sol-gel method and high-temperature calcination, preparing a composite filler. The mica, with its sheet-like shape, forms a large-area protective layer that can delay the diffusion and penetration of corrosive media. At the same time, zinc oxide has a broad-spectrum antibacterial effect, and the zinc oxide coating on the mica significantly improves the mechanical and anti-corrosion properties of the coating. In addition, the hydrophobicity of the composite filler is improved by modifying it with the silane coupling agent KH550, which also improves the compatibility of the composite filler with the matrix material and avoids the aggregation of the composite filler. Furthermore, the grafted amino groups can participate in the curing of epoxy resin together with the curing agent, so that its comprehensive performance can be fully utilized. Detailed Implementation

[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1: A method for preparing silica nanotubes includes the following steps:

[0035] C1. 100 mg of hydroxylated carbon nanotubes were dispersed in 50 mL of toluene-2,4-diisocyanate and reacted at 80 °C for 72 h under nitrogen protection. After the reaction was completed, the mixture was filtered, washed and dried to prepare isocyanate-based carbon nanotubes.

[0036] C2. Take 10 mg of isocyanate-derived carbon nanotubes, 400 mg of polyethylene glycol (Mn=4000 g / mol) and 10 mL of toluene in a reactor, and disperse them ultrasonically at 60 °C for 25 min under nitrogen protection. Then, react them at 100 °C for 36 h. After the reaction is completed, filter, wash and dry to prepare modified carbon nanotubes.

[0037] C3. Take 5 mg of modified carbon nanotubes and ultrasonically disperse them in 100 mL of 95% ethanol solution. Add 0.1 mL of tetraethyl orthosilicate and ultrasonically disperse for another 20 min. Then add 0.1 mL of 25% ammonia solution. Stir and react at room temperature for 24 h and let stand for aging. After filtration, washing and drying, place the obtained silica-coated modified carbon nanotubes in an air atmosphere at 500 °C for 6 h to prepare silica nanotubes.

[0038] Example 2: A method for preparing modified silica nanotubes includes the following steps:

[0039] A. Take 27.2g pentaerythritol, 100mL chlorobenzene, 76.6g phosphorus oxychloride and 0.1g 4-dimethylaminopyridine into a reactor. The reaction is protected by nitrogen gas and placed at 65℃ for 2h. Then the temperature is raised to 98℃ and the reaction is continued for 8h. After the reaction is completed, the heating is stopped and the mixture is allowed to stand for 10h. The product is filtered, washed with dichloromethane, and dried under vacuum to prepare spirocyclic phosphate diacyl chloride.

[0040] B. Take 29.7g of spirocyclic phosphate diacyl chloride and 100mL of acetonitrile in a reactor, heat to 60℃ under a nitrogen atmosphere, take 13.4g of 2-aminobenzimidazole, 10g of 3,5-diamino-1,2,4-triazole and 50mL of anhydrous methanol, stir and mix evenly, then add to the reactor, place at 70℃ and stir to react for 8h. After the reaction is completed, filter, wash and dry to prepare the amination modifier;

[0041] C. Take 1g of the silica nanotubes prepared in Example 1 and ultrasonically disperse them in 50mL of acetone solvent. Then add 0.4g of 4-isocyanobenzoyl chloride and 0.01g of dibutyltin dilaurate and stir to mix. Place the mixture at 50℃ and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare acyl chloride silica nanotubes.

[0042] D. Take 1g of acyl chloride silica nanotubes and ultrasonically disperse them in 80mL of tetrahydrofuran solvent. Then add 0.7g of amylating modifier and 0.02g of pyridine and stir to mix. Place the mixture at 30℃ and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare modified silica nanotubes.

[0043] Example 3: A method for preparing a modified composite filler includes the following steps:

[0044] (1) Take 0.5g of tris(hydroxymethyl)aminomethane and 300mL of deionized water in a reactor, adjust the pH to 8.5 with 0.1mol / L hydrochloric acid, then add 0.3g of ground mica powder, disperse it evenly by ultrasonication, and then add 0.3g of dopamine hydrochloride while stirring. Stir the reaction at room temperature for 24h. After the reaction is completed, filter, wash and dry to prepare dopamine-modified mica.

[0045] (2) Take 75 mg of dopamine-modified mica and ultrasonically disperse it in 20 mL of ethanol and 50 mL of deionized water. Heat it to 70 °C, add 2.4 g of zinc nitrate hexahydrate and 0.02 g of dispersant polyethylene glycol, stir and react for 1 h, then add dropwise a mixed solution of 2.5 mL of ammonia water and 30 mL of deionized water. After the dropwise addition is complete, continue to react for 2 h. After the reaction is complete, filter, wash and dry, grind and put it into a tube furnace, calcine it at 1000 °C for 2 h, with a heating rate of 10 °C / min, to prepare the composite filler;

[0046] (3) Take 50 mg of composite filler and ultrasonically disperse it in a mixed solution of 30 mL of anhydrous ethanol and 0.05 g of silane coupling agent KH550. Stir and react at 70 °C for 3 h. Then slowly add 30 mL of deionized water and stir and react for 3 h. After the reaction is completed, filter, wash and dry to prepare the modified composite filler.

[0047] Example 4 A corrosion-resistant coating comprising the following components by weight: 48 parts of waterborne epoxy resin, 7.5 parts of modified silica nanotubes prepared in Example 2, 4.2 parts of modified composite filler prepared in Example 3, 5.5 parts of curing agent m-phenylenediamine, 0.8 parts of wetting agent polydimethylsiloxane, 0.4 parts of defoamer fatty alcohol polyoxyethylene ether, 0.3 parts of leveling agent sodium polyacrylate, and 0.2 parts of dispersant BYK-190.

[0048] The preparation method of the above-mentioned corrosion-resistant coating includes the following steps: weigh each raw material according to the weight parts, mix the water-based epoxy resin and dispersant evenly, then add modified silica nanotubes, modified composite fillers, wetting agents and leveling agents and stir evenly, then add curing agents and defoamers and continue to stir evenly to prepare a corrosion-resistant coating.

[0049] Example 5 A corrosion-resistant coating comprising the following components by weight: 60 parts of waterborne epoxy resin, 10 parts of modified silica nanotubes prepared in Example 2, 6.8 parts of modified composite filler prepared in Example 3, 8.5 parts of curing agent m-phenylenediamine, 1.7 parts of wetting agent polydimethylsiloxane, 0.7 parts of defoamer alkylphenol polyoxyethylene ether, 0.5 parts of leveling agent sodium polyacrylate, and 0.4 parts of dispersant BYK-191.

[0050] The preparation method of the above corrosion-resistant coating is the same as in Example 4.

[0051] Example 6 A corrosion-resistant coating comprising the following components by weight: 67 parts of waterborne epoxy resin, 14 parts of modified silica nanotubes prepared in Example 2, 8.5 parts of modified composite filler prepared in Example 3, 10.5 parts of curing agent m-phenylenediamine, 2.1 parts of wetting agent polydimethylsiloxane, 0.8 parts of defoamer fatty alcohol polyoxyethylene ether, 0.7 parts of leveling agent sodium polyacrylate, and 0.5 parts of dispersant BYK-190.

[0052] The preparation method of the above corrosion-resistant coating is the same as in Example 4.

[0053] Comparative Example 1: A method for preparing a modified composite filler includes the following steps:

[0054] 20 mg of mica and 30 mg of zinc oxide were ultrasonically dispersed in a mixed solution of 30 mL of anhydrous ethanol and 0.05 g of silane coupling agent KH550. The mixture was stirred at 70 °C for 3 h. Then, 30 mL of deionized water was slowly added dropwise and the mixture was stirred for another 3 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified composite filler.

[0055] Comparative Example 2: A corrosion-resistant coating comprising the following components by weight: 67 parts of waterborne epoxy resin, 14 parts of nano-silica, 8.5 parts of the modified composite filler prepared in Example 3, 10.5 parts of m-phenylenediamine as a curing agent, 2.1 parts of polydimethylsiloxane as a wetting agent, 0.8 parts of fatty alcohol polyoxyethylene ether as a defoamer, 0.7 parts of sodium polyacrylate as a leveling agent, and 0.5 parts of BYK-190 as a dispersant.

[0056] The preparation method of the above corrosion-resistant coating is the same as in Example 4.

[0057] Comparative Example 3: A corrosion-resistant coating comprising the following components by weight: 67 parts of waterborne epoxy resin, 14 parts of silica nanotubes prepared in Example 1, 8.5 parts of modified composite filler prepared in Example 3, 10.5 parts of curing agent m-phenylenediamine, 2.1 parts of wetting agent polydimethylsiloxane, 0.8 parts of defoamer fatty alcohol polyoxyethylene ether, 0.7 parts of leveling agent sodium polyacrylate, and 0.5 parts of dispersant BYK-190.

[0058] The preparation method of the above corrosion-resistant coating is the same as in Example 4.

[0059] Comparative Example 4: A corrosion-resistant coating comprising the following components by weight: 67 parts of waterborne epoxy resin, 14 parts of modified silica nanotubes prepared in Example 2, 8.5 parts of modified composite filler prepared in Comparative Example 1, 10.5 parts of curing agent m-phenylenediamine, 2.1 parts of wetting agent polydimethylsiloxane, 0.8 parts of defoamer fatty alcohol polyoxyethylene ether, 0.7 parts of leveling agent sodium polyacrylate, and 0.5 parts of dispersant BYK-190.

[0060] The preparation method of the above corrosion-resistant coating is the same as in Example 4.

[0061] Performance testing

[0062] The corrosion-resistant coatings prepared in Examples 4-6 and Comparative Examples 2-4 were applied to the polished AA2024 aluminum alloy substrate using a wire rod. The coatings were cured at room temperature for 24 hours and then at 60°C for 12 hours. Performance testing was then performed.

[0063] (1) The impact resistance, adhesion and pencil hardness of the coating were tested according to the methods specified in GB / T 1732-2020, GB / T9286-2021 and GB / T 6739-2022 respectively. The data results are shown in Table 1.

[0064] (2) Corrosion resistance test: The test was conducted in accordance with GB / T 9274-1988. The acid resistance was tested with 10% sulfuric acid solution, the alkali resistance with 10% sodium hydroxide solution, and the salt resistance with 5% sodium chloride solution. The test ended when the coating showed blistering, rusting or severe discoloration. Slight discoloration was allowed. The data results are shown in Table 1.

[0065] (3) Thermal insulation performance test: The heat source temperature is 250℃. After 60min and 420min of thermal insulation test, the temperature difference between the heat source and the surface of the coated sample is measured. The data results are shown in Table 1.

[0066] (4) Flame retardant performance test: The data results obtained by limiting oxygen index test are shown in Table 1.

[0067] (5) Antibacterial performance test: The antibacterial rate test was conducted in accordance with GB / T 21866-2008. The test strain was Staphylococcus aureus. The data results are shown in Table 1.

[0068] Table 1 Sample performance test results

[0069]

[0070] As can be seen from the data in Table 1, the coatings prepared in Examples 4-6 of this invention have strong adhesion, high impact strength and pencil hardness, and good corrosion resistance, heat insulation, flame retardant effect and antibacterial effect. In Comparative Example 2, modified silica nanotubes were replaced with an equal amount of nano-silica. In Comparative Example 3, no modification treatment was performed on the silica nanotubes. The mechanical properties, limiting oxygen index, and antibacterial rate of Comparative Examples 2-3 were found to be lower than those of Examples 4-6. This may be due to the agglomeration of nanoparticles leading to a decrease in mechanical properties. At the same time, the lack of introduction of antibacterial benzimidazole groups, synergistic flame-retardant phosphorus and nitrogen elements led to a decrease in flame-retardant performance and antibacterial effect. Furthermore, the impact strength and thermal insulation temperature difference of Comparative Example 2 were found to be significantly lower than those of Examples 4-6, indicating that the addition of modified silica nanotubes can improve the mechanical properties, thermal insulation performance, flame-retardant effect, and antibacterial effect of the coating. In Comparative Example 4, mica and zinc oxide were simply mixed. The pencil hardness, impact strength, corrosion resistance, and thermal insulation temperature difference were found to be lower than those of Examples 4-6, indicating that the addition of modified composite filler improved the mechanical properties, corrosion resistance, and thermal insulation effect of the coating to a certain extent.

[0071] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A corrosion resistant coating, characterized in that, The composition comprises the following components by weight: 45-70 parts of water-based epoxy resin, 7-16 parts of modified silica nanotube, 4-9 parts of modified composite filler, 5-12 parts of curing agent, 0.5-2.5 parts of wetting agent, 0.3-1 part of defoaming agent, 0.2-0.8 part of leveling agent, and 0.1-0.6 part of dispersing agent; The modified silica nanotube is prepared by acylating the silica nanotube with 4-isocyanobenzoyl chloride and then reacting with an amination modifier; the amination modifier is synthesized by using pentaerythritol and phosphorus oxychloride as raw materials to synthesize spirophosphate diacyl chloride, and then using 2-aminobenzimidazole and 3,5-diamino-1,2,4-triazole to respectively substitute the chlorine atoms at both ends of the spirophosphate diacyl chloride; The silica nanotube is prepared by reacting toluene-2,4-diisocyanate with hydroxylated carbon nanotubes to obtain isocyanate carbon nanotubes, and then covalently grafting polyethylene glycol to prepare modified carbon nanotubes, and then using the modified carbon nanotubes as a template, using tetraethyl orthosilicate as a raw material, and using a sol-gel method under alkaline conditions and removing the template by heat treatment to obtain the silica nanotube; The modified composite filler is prepared by modifying the composite filler with silane coupling agent KH550; the composite filler is prepared by using dopamine to self-polymerize a polydopamine layer on the outer surface of mica, and then using a sol-gel method and high-temperature calcination to wrap a layer of zinc oxide on the outer layer of dopamine-modified mica; The preparation method of the modified composite filler comprises the following steps: (1) Put trimethylol aminomethane and deionized water into a reactor, adjust the pH to 8.5 with hydrochloric acid, then add ground mica powder, ultrasonic dispersion, then add hydrochloric acid dopamine under stirring, stir at room temperature for 20-24 h, after the reaction is completed, filter, wash, dry, and prepare dopamine-modified mica; (2) Ultrasonic dispersion of dopamine-modified mica in ethanol and deionized water, heating to 65-75℃, adding zinc nitrate hexahydrate and dispersant polyethylene glycol, stirring for 1-1.5 h, then adding a mixed solution of ammonia and deionized water dropwise, continuing to react for 1.5-2 h after the dropwise addition is completed, after the reaction is completed, filter, wash, dry, grind, and then put into a tube furnace, calcine at 950-1000℃ for 2-2.5 h, and prepare the composite filler; (3) Ultrasonic dispersion of the composite filler in a mixed solution of anhydrous ethanol and silane coupling agent KH550, stirring at 55-70℃ for 3-5 h, then slowly adding deionized water, stirring for 2-3 h, after the reaction is completed, filter, wash, dry, and prepare the modified composite filler.

2. The corrosion resistant coating of claim 1, wherein, The preparation method of the modified silica nanotube comprises the following steps: A, take pentaerythritol, chlorobenzene, phosphorus oxychloride and 4-dimethylamino pyridine in a reactor, protect with nitrogen gas, heat to 60-70℃ for 2-3 h, then heat to 95-100℃, continue to react for 6-8 h, after the reaction is completed, stop heating and stand for 8-10 h, filter the product, wash with dichloromethane, and dry under vacuum to prepare spirophosphate diacyl chloride; B. Spirocyclic phosphate diacyl chloride and acetonitrile were placed in a reactor and heated to 50-60℃ under a nitrogen atmosphere. 2-aminobenzimidazole, 3,5-diamino-1,2,4-triazole and anhydrous methanol were stirred and mixed evenly, and then added to the reactor. The mixture was stirred and reacted at 65-75℃ for 6-8 hours. After the reaction was completed, the mixture was filtered, washed and dried to prepare the amination modifier. C. Disperse silica nanotubes ultrasonically in acetone solvent, then add 4-isocyanobenzoyl chloride and dibutyltin dilaurate and stir to mix. Place the mixture at 40~60℃ and stir to react for 12~24h. After the reaction is completed, filter, wash and dry to prepare acyl chloride silica nanotubes. D. Acyl chloride silica nanotubes were ultrasonically dispersed in tetrahydrofuran solvent, and then an amino modifier and pyridine were added and stirred. The mixture was placed at 25~40℃ and stirred for 6~18h. After the reaction was completed, the modified silica nanotubes were prepared by filtration, washing and drying.

3. The corrosion resistant coating of claim 2, wherein, In step A, the molar ratio of pentaerythritol to phosphorus oxychloride is 1:2~2.5; in step B, the molar ratio of spirocyclic phosphate diacyl chloride, 2-aminobenzimidazole, and 3,5-diamino-1,2,4-triazole is 1:1~1.1:1~1.

1.

4. The corrosion resistant coating of claim 2, wherein, The preparation method of silica nanotubes in step C includes the following steps: C1. Hydroxylated carbon nanotubes were dispersed in toluene-2,4-diisocyanate and reacted at 75-85℃ for 70-72h under nitrogen protection. After the reaction was completed, the nanotubes were filtered, washed and dried to prepare isocyanate-based carbon nanotubes. C2. Isocyanated carbon nanotubes, polyethylene glycol and toluene are placed in a reactor and ultrasonically dispersed at 55-70℃ for 20-30 min under nitrogen protection. Then, the mixture is reacted at 90-100℃ for 30-36 h. After the reaction is completed, the mixture is filtered, washed and dried to prepare modified carbon nanotubes. C3. The modified carbon nanotubes were ultrasonically dispersed in an ethanol solution, and tetraethyl orthosilicate was added dropwise. The mixture was then ultrasonically dispersed for 20-30 minutes, followed by the addition of ammonia. The mixture was stirred and reacted at room temperature for 20-24 hours, and then allowed to stand for aging. After filtration, washing, and drying, the modified carbon nanotubes coated with silica were calcined in air at 480-520°C for 5-7 hours to prepare silica nanotubes.

5. The corrosion resistant coating of claim 2, wherein, In step D, the mass ratio of acyl chloride silica nanotubes to aminated modifier is 1:0.5~1.

6. The corrosion resistant coating of claim 1, wherein, In step (2), the mass ratio of dopamine-modified mica to zinc nitrate hexahydrate is 0.07~0.08:2.4; the heating rate of the tube furnace is 8~10℃ / min.

7. The corrosion resistant coating of claim 1, wherein, The curing agent is an amine-based curing agent; the wetting agent is polydimethylsiloxane; the defoamer is one of fatty alcohol polyoxyethylene ether or alkylphenol polyoxyethylene ether; the leveling agent is sodium polyacrylate; and the dispersant is one of BYK-190 or BYK-191.

8. The corrosion resistant coating of claim 1, wherein, The preparation method of the corrosion-resistant coating comprises the following steps: weighing raw materials according to weight parts, uniformly mixing the water-based epoxy resin with the dispersant, then uniformly stirring the modified silicon dioxide nanotube, the modified composite filler, the wetting agent and the leveling agent, subsequently uniformly stirring the curing agent and the defoaming agent, and preparing the corrosion-resistant coating.

9. Use of a corrosion resistant coating according to claim 1, characterized in that, The corrosion-resistant coating is coated on the surface of the aluminum alloy heat exchange pipe through a coating method.

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