Anticorrosive steel pipe powder coating and preparation method thereof

Abstract

The application discloses a kind of anticorrosive steel pipe powder coating and preparation method thereof, it is related to powder coating technical field;The anticorrosive steel pipe powder coating is composed of anticorrosive synergistic filler, modified epoxy resin, dicyandiamide curing agent, levelling agent and 2-methyl imidazole accelerator;Anticorrosive synergistic filler is uniformly and stably dispersed in modified epoxy resin by chemical bonding and physical bonding, effectively improve the interface compatibility and combination of both, not only rely on dense physical barrier, electrochemical protection and self-repairing multiple action mode to enhance the anticorrosive ability of powder coating, also significantly improve the adhesion, reduce the risk of crack, fracture and fall after powder coating solidification, prolong the service cycle of coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of powder coating, and particularly relates to a kind of anticorrosive steel pipe powder coating and its preparation method. BACKGROUND

[0002] The powder coating is 100% solid component, does not contain any organic solvent, and almost does not produce volatile organic compounds in the production and use process, is friendly to the environment; the coating can form a dense, continuous, non-porous film on the surface of the steel pipe, effectively isolates water, oxygen, chloride ion, sulfur dioxide and other corrosive media from contacting the steel pipe matrix, the rust-proof pigment in the coating can react with the surface of the steel pipe to form a passivation film, inhibit the electrochemical corrosion reaction, and the high-quality powder coating has excellent hardness, toughness and adhesion, can withstand mechanical impact, wear and tear and stress during transportation and installation, etc., prevents the coating from being damaged and causes corrosion, in order to further enhance the corrosion resistance of the coating or functional effect, different types of fillers can be added to improve the comprehensive performance of the coating; in short, the powder coating forms a strong, durable and efficient protective layer on the surface of the steel pipe by electrostatic spraying and high-temperature curing, to resist corrosion of the steel pipe in various environments, thereby prolonging its service life, at the same time, the powder not adhered to the steel pipe during spraying can be collected by the recycling system for reuse, the utilization rate can be as high as more than 99%, reducing waste.

[0003] The existing technology mainly has the following problems:

[0004] The dispersibility of the filler in the powder coating is poor, which limits the application effect, is not conducive to enhancing the corrosion resistance, and also causes the adhesion between the powder coating and the matrix to be weak after curing, which is prone to cracking, brittle cracking or peeling. SUMMARY

[0005] In view of the above situation, in order to overcome the defects of the prior art, the present application provides an anticorrosive steel pipe powder coating, which comprises the following components by weight: 10-20 parts of anticorrosive synergistic filler, 60-80 parts of modified epoxy resin, 3-5 parts of dicyandiamide curing agent, 1-3 parts of leveling agent and 0.4-0.8 parts of 2-methylimidazole accelerator.

[0006] The anticorrosive synergistic filler is made of the following components by weight: 10-20 parts of polypyrrole-coated graphene composite powder, 8-10 parts of pyrrole, 8-10 parts of gamma-aminopropyl triethoxysilane, 1.0-1.5 parts of benzotriazole and 18-22 parts of ammonium persulfate.

[0007] The modified epoxy resin comprises the following components by weight: 80-100 parts of bisphenol A type epoxy resin, 10-20 parts of phenolic epoxy resin, 8-10 parts of polypropylene glycol diglycidyl ether, 50-60 parts of octadecanedioic acid and 5-10 parts of gallic acid.

[0008] The preparation method of the anticorrosion synergistic filler specifically comprises the following steps:

[0009] (1) 0.6-0.8 g of cetyltrimethylammonium bromide and 25 mL of deionized water are magnetically stirred for 20-30 min, and then fluorinated graphene is slowly added and magnetically stirred for another 20-30 min, followed by ultrasonic dispersion treatment for 30-40 min, 600-800 rpm centrifugation for 5-10 min, collection of the supernatant to obtain dispersion liquid I, 0.5-1.5 g of pyrrole is added to 30 mL of 50% ethanol solution, ultrasonic treatment for 20-30 min to obtain solution II, 1.8-3.0 g of anhydrous ferric chloride is dissolved in 20 mL of deionized water, ultrasonic treatment for 20-30 min to obtain solution III, then the dispersion liquid I and the solution II are mixed under the condition of 0-5℃ ice bath, and the solution III is added dropwise after uniform stirring, followed by stirring for 12-24 h after dropwise addition, centrifugation, collection of the solid product and washing with deionized water until the pH is 7.0, drying, and in-situ polymerization of polypyrrole on the surface and edges of the fluorinated graphene sheet to form a continuous, dense and uniform coating layer, which not only enhances the labyrinth effect of the fluorinated graphene, prolongs the path and time of the diffusion of corrosion media such as water, oxygen and chloride ions to the surface of the steel pipe, but also improves the wettability and dispersibility of the fluorinated graphene, reduces the stacking and agglomeration, wherein the long molecular chain of the polypyrrole can intertwine and interpenetrate with the molecular chain of the epoxy resin to form a firm physical combination, which is conducive to the formation of strong and tough interface combination and reduces the risk of peeling, and a polypyrrole-coated graphene composite powder is obtained;

[0010] (2) dispersing the polypyrrole-coated graphene composite powder of step (1) in 50 mL of deionized water, ultrasonic dispersion treatment for 2-3 h to obtain a polypyrrole-coated graphene dispersion solution, then adding 0.8-1.0 g of pyrrole into 150 mL of 50% ethanol solution, stirring for 20-30 min, then adding γ-aminopropyl triethoxysilane and benzotriazole, continuing to stir for 30-40 min, then adding into the polypyrrole-coated graphene dispersion solution, then slowly adding ammonium persulfate solution at a speed of 1000-2000 rpm, reacting in an ice water bath at 0-5°C for 10-12 h, wherein the ammonium persulfate solution is prepared by dissolving 1.8-2.2 g of ammonium persulfate in 10-20 mL of deionized water, after the reaction is completed, performing suction filtration, washing, drying the precipitate, and crushing, in this process, the polypyrrole-coated graphene composite powder is taken as the core, γ-aminopropyl triethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer, and the polypyrrole layer generated by secondary polymerization is taken as the outermost layer, firmly anchoring and embedding the intermediate layer, the chemical bonding of γ-aminopropyl triethoxysilane and the physical bonding formed by the entanglement and interpenetration of the outermost polypyrrole molecular chain present excellent and stable dispersion, at the same time, the amino group of γ-aminopropyl triethoxysilane can not only bridge the filler and the epoxy resin, but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, thereby improving the adhesion, and the coating layer with excellent compatibility and adhesion can maximize the multiple physical barrier effect, effectively block the penetration of corrosive media, greatly improve the corrosion resistance, and obtain a corrosion-increasing filler;

[0011] Preferably, in step (1), the amount of fluorinated graphene added is 0.5-1.0 g, the surface of the fluorinated graphene is hydrophobic, reducing the water permeability and delaying the invasion of corrosive media from the source, the C-F bond of the fluorinated graphene is very stable, and the fluorinated graphene itself is resistant to acid, alkali and solvent, providing an extremely stable and durable physical and chemical barrier, and the fluorinated graphene is an insulator, completely avoiding the risk of forming an electric couple with the steel substrate at the coating defect to accelerate metal corrosion;

[0012] Preferably, in step (2), the amounts of γ-aminopropyl triethoxysilane and benzotriazole added are 0.8-1.0 mL and 0.10-0.15 g, respectively, the γ-aminopropyl triethoxysilane can prevent the penetration of corrosive media along the filler-resin interface or the coating-metal interface, enhancing the interface corrosion resistance, when the corrosive medium penetrates the coating and contacts the surface of the steel pipe, the benzotriazole will quickly migrate to the metal surface and chemisorb, forming a dense monomolecular protective film, effectively inhibiting the corrosion current and preventing corrosion from spreading at the damage, and imparting the ability of self-repairing to the damage.

[0013] This invention also provides a method for preparing anti-corrosion steel pipe powder coating, specifically including the following steps:

[0014] S1. Add 8.0-10.0g of bisphenol A epoxy resin, 1.0-2.0g of phenolic epoxy resin, 0.8-1.0g of polypropylene glycol diglycidyl ether, 5.0-6.0g of octadecanoic acid, and 0.5-1.0g of gallic acid sequentially to a reaction vessel, and purge the air from the reaction vessel with nitrogen. Heat to 90-95℃ and stir for 20-30 minutes. Then add 0.01g of triphenylphosphine and heat to 120-140℃, maintaining the temperature while continuously stirring until the acid value is <5mgKOH / g. Stop the reaction, cool, and chemically modify the mixed epoxy resin with octadecanoic acid and gallic acid to produce… An epoxy ester resin with flexible long chains and phenolic hydroxyl groups is obtained. The flexible long chains introduced by octadecanoic acid not only disrupt the regularity of the epoxy resin molecular chain and reduce the intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also improve flexibility. The internal stress generated when the coating is cured and cooled or subjected to external impact can be effectively absorbed and released by the flexible chain segments, improving adhesion and avoiding coating brittleness, cracking or peeling caused by excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of metal substrates, generating strong physical adsorption and enhancing interfacial bonding, thus obtaining a modified epoxy resin.

[0015] S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at a speed of 800-1200 rpm for 5-10 minutes to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 100-110℃ and the screw speed to 200-400 rpm. After extrusion, the mixture is cooled to room temperature, and the resulting extrudate is then pulverized. The anti-corrosion synergistic filler is uniformly dispersed in the modified epoxy resin, and the two are tightly bonded together. With the synergy of other additives, a uniform, dense, and multi-layered anti-corrosion powder coating system is constructed, which significantly improves the adhesion and anti-corrosion properties of the coating and extends the service life of the coating, thus obtaining an anti-corrosion steel pipe powder coating.

[0016] Preferably, in step S1, the bisphenol A type epoxy resin is type E-20 and the phenolic epoxy resin is type F51. E-20 is the main skeleton of the resin system, providing integrity, mechanical strength and basic adhesion. F51 is a performance enhancer, which is inserted into the main skeleton of E-20 like steel bars, improving the resin's corrosion resistance and mechanical strength. The combination of the two maintains both super corrosion resistance and heat resistance, while ensuring good processability and a certain degree of toughness, avoiding brittleness problems.

[0017] The beneficial effects achieved by this invention are as follows:

[0018] This invention effectively improves the interfacial compatibility and bonding between anti-corrosion and synergistic fillers by uniformly and stably dispersing them in modified epoxy resin through chemical bonding and physical adhesion. This not only enhances the anti-corrosion capability of powder coatings through multiple mechanisms such as a dense physical barrier, electrochemical protection, and self-healing, but also significantly improves adhesion, reduces the risk of cracking, breakage, and peeling after curing, and extends the service life of the coating. In the anti-corrosion and synergistic filler, the polypyrrole generated during the first polymerization coats the surface and edges of the fluorinated graphene sheets, enhancing the fluorinated graphene... The labyrinth effect of graphene prolongs the path and time for corrosive media to diffuse to the steel pipe surface, and also improves the wettability and dispersibility of fluorinated graphene, reducing stacking and agglomeration. Using polypyrrole-coated graphene composite powder as the core, γ-aminopropyltriethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer. The polypyrrole layer generated by the second polymerization serves as the outermost coating, firmly anchoring the γ-aminopropyltriethoxysilane in the intermediate layer and exposing the amino groups and benzotriazole embedded within. The chemical properties of γ-aminopropyltriethoxysilane... The bonding effect, along with the physical bonding caused by the entanglement and interpenetration of the outer polypyrrole molecular chains, effectively eliminates the risk of interfacial separation between the filler and epoxy resin, achieving excellent and stable dispersibility of the filler. Simultaneously, the amino groups of γ-aminopropyltriethoxysilane not only bridge the filler and epoxy resin but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, constructing a robust chemical anchoring point between the filler, resin, and metal substrate, thus enhancing adhesion. Furthermore, coatings with excellent compatibility, dispersibility, and adhesion can further leverage the multiple physical barriers. To maximize the effectiveness of the coating, it effectively blocks the penetration of corrosive media and greatly improves the anti-corrosion performance. Fluorinated graphene, as an insulator, provides electrochemical protection, avoiding the risk of accelerated metal corrosion caused by the formation of an electric couple between the coating defects and the steel substrate. Benzotriazole's damage self-healing ability can be quickly released and migrated to the metal surface to form a protective film, effectively inhibiting corrosion current and preventing the corrosion from spreading further. Furthermore, the outer polypyrrole also has a certain degree of toughness, which can play a role in buffering and stress relaxation, making the filler both rigid and flexible, and improving the risk of cracks and brittle fracture after the coating is cured.In the modified epoxy resin, octadecanoic acid and gallic acid chemically modify the mixed epoxy resin. The flexible long chains introduced by octadecanoic acid not only disrupt the regularity of the epoxy resin molecular chains and reduce intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also absorb and release internal stress generated during coating curing and cooling or external impact through flexible chain segments, thereby improving adhesion and preventing coating brittleness, cracking, or peeling caused by excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of the metal substrate, generating strong physical adsorption and enhancing the interface. The long fatty chains impart excellent hydrophobicity, effectively blocking the penetration of water molecules and corrosive ions. They also prevent the coating from developing microcracks during thermal expansion and contraction or slight deformation, maintaining the integrity of the barrier. Gallic acid acts as small cross-linking points, reacting with multiple epoxy molecules to improve the coating's density and significantly enhance its anti-corrosion performance. This invention uses anti-corrosion synergistic fillers, modified epoxy resin, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator to create an anti-corrosion steel pipe powder coating. This improves the dispersibility of the filler, enhances anti-corrosion performance, and also improves adhesion to the substrate, effectively extending the service life of the powder coating. Attached Figure Description

[0019] Figure 1 These are adhesion results diagrams for Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0020] Figure 2 The images show the maximum corrosion length results for Examples 1-4 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0023] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0024] Example 1

[0025] This embodiment proposes an anti-corrosion steel pipe powder coating, comprising the following components in parts by weight: 20 parts of anti-corrosion and enhancing filler, 80 parts of modified epoxy resin, 5 parts of dicyandiamide curing agent, 3 parts of leveling agent, and 0.8 parts of 2-methylimidazole accelerator.

[0026] The corrosion-resistant and enhanced filler is made from the following components in parts by weight: 20 parts of polypyrrole-coated graphene composite powder, 10 parts of pyrrole, 10 parts of γ-aminopropyltriethoxysilane, 1.5 parts of benzotriazole, and 22 parts of ammonium persulfate.

[0027] The modified epoxy resin comprises the following components in parts by weight: 100 parts of bisphenol A type epoxy resin, 20 parts of phenolic epoxy resin, 10 parts of polypropylene glycol diglycidyl ether, 60 parts of octadecanoic acid, and 10 parts of gallic acid.

[0028] The preparation method of corrosion-resistant and corrosion-enhancing fillers specifically includes the following steps:

[0029] (1) Stir 0.8g of hexadecyltrimethylammonium bromide and 25mL of deionized water magnetically for 30min, then slowly add fluorinated graphene. The amount of fluorinated graphene added is 1.0g. Fluorinated graphene has a hydrophobic surface, which reduces water permeability and delays the intrusion of corrosive media from the source. The CF bond of fluorinated graphene is very stable. It is resistant to acid, alkali and solvent, providing an extremely stable and durable physicochemical barrier. Fluorinated graphene is also an insulator, which completely avoids the risk of forming an electric couple with the steel substrate at the coating defect and accelerating metal corrosion. Continue stirring magnetically for 30min, then perform ultrasonic dispersion treatment for 40min, centrifuge at 800rpm for 10min, collect the supernatant to obtain dispersion I, then add 1.5g of pyrrole to 30mL of 50% ethanol solution, and sonicate for 30min to obtain solution II. Dissolve 3.0g of anhydrous ferric chloride in 20 mL of deionized water was used to sonicate for 30 min to obtain solution III. Then, under an ice bath at 5 °C, dispersion I and solution II were mixed and stirred evenly before adding solution III dropwise. After the addition was complete, the mixture was stirred for 24 h, centrifuged, and the solid product was collected and washed with deionized water until the pH reached 7.0. After drying, polypyrrole was found to be coated on the surface and edges of fluorinated graphene sheets through in-situ polymerization, forming a continuous, dense, and uniform coating layer. This not only enhanced the labyrinth effect of fluorinated graphene and prolonged the path and time for corrosive media such as water, oxygen, and chloride ions to diffuse to the surface of the steel pipe, but also improved the wettability and dispersibility of fluorinated graphene, reducing stacking and agglomeration. In particular, the long molecular chains of polypyrrole can entangle and interpenetrate with the molecular chains of epoxy resin to form a strong physical bond, which is conducive to forming a strong and tough interfacial bond and reducing the risk of peeling. The resulting composite powder of polypyrrole-coated graphene was obtained.

[0030] (2) Disperse the polypyrrole-coated graphene composite powder obtained in step (1) in 50 mL of deionized water and ultrasonically disperse it for 3 h to obtain a polypyrrole-coated graphene dispersion solution for later use. Then add 1.0 g of pyrrole to 150 mL of 50% ethanol solution and stir for 30 min. Next, add γ-aminopropyltriethoxysilane and benzotriazole. The amount of γ-aminopropyltriethoxysilane and benzotriazole added is 1.0 mL and 0.15 g, respectively. γ-aminopropyltriethoxysilane can prevent corrosion. The medium penetrates along the filler-resin interface or coating-metal interface, enhancing the interfacial corrosion resistance. When the corrosive medium penetrates the coating and comes into contact with the steel pipe surface, benzotriazole rapidly migrates to the metal surface and undergoes chemical adsorption, forming a dense monomolecular protective film. This effectively inhibits corrosion current, prevents corrosion from spreading at the damage site, and endows the damage with self-repairing capabilities. After stirring for 40 minutes, it is added to the polypyrrole-coated graphene dispersion solution, followed by the slow addition of ammonium persulfate solution at 2000 rpm, and then heated to 5°C. The reaction was carried out in a water bath for 12 hours. The ammonium persulfate solution was prepared by dissolving 2.2 g of ammonium persulfate in 20 mL of deionized water. After the reaction, the mixture was filtered, washed, and the precipitate was dried and pulverized. In this process, polypyrrole-coated graphene composite powder serves as the core. γ-aminopropyltriethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer. The polypyrrole layer generated by secondary polymerization acts as the outermost layer, firmly anchoring and embedding the intermediate layer. γ-aminopropyltriethoxysilane... The chemical bonding and the physical bonding formed by the entanglement and interpenetration of the outer polypyrrole molecular chains exhibit excellent and stable dispersibility. At the same time, the amino groups of γ-aminopropyltriethoxysilane can not only bridge the filler and epoxy resin, but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, thereby improving adhesion. Furthermore, the coating with excellent compatibility, dispersibility and adhesion can maximize the effect of multiple physical barriers, effectively block the penetration of corrosive media, greatly improve the anti-corrosion performance, and obtain an anti-corrosion and enhanced filler.

[0031] This embodiment provides a method for preparing anti-corrosion steel pipe powder coating, specifically including the following steps:

[0032] S1. 10.0g of bisphenol A epoxy resin, 2.0g of phenolic epoxy resin, 1.0g of polypropylene glycol diglycidyl ether, 6.0g of octadecanoic acid, and 1.0g of gallic acid are sequentially added to the reactor. The bisphenol A epoxy resin is type E-20, and the phenolic epoxy resin is type F51. E-20 forms the main framework of the resin system, providing integrity, mechanical strength, and basic adhesion. F51 is a performance enhancer, acting like reinforcing bars within the E-20 framework, improving the resin's corrosion resistance and mechanical strength. The combination of these two components maintains superior corrosion and heat resistance while ensuring good processability and a certain degree of toughness, avoiding brittleness issues. Nitrogen gas is introduced to displace the air in the reactor. The temperature is raised to 95℃ and stirred for 30 minutes. Then, 0.01g of triphenylphosphine is added, and the temperature is raised to 140℃. The mixture is held at this temperature. The reaction was continued until the acid value was <5 mg KOH / g, at which point the reaction was stopped and cooled. The mixed epoxy resin was chemically modified by octadecanoic acid and gallic acid to generate an epoxy ester resin with flexible long chains and phenolic hydroxyl groups. The flexible long chains introduced by octadecanoic acid not only disrupted the regularity of the epoxy resin molecular chains and reduced the intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also improved the flexibility. The internal stress generated when the coating is cured and cooled or subjected to external impact can be effectively absorbed and released by the flexible chain segments, improving the adhesion and avoiding the coating from becoming brittle, cracking or peeling off due to excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of metal substrates, generating strong physical adsorption and enhancing the interfacial bonding force, thus obtaining the modified epoxy resin.

[0033] S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at 1200 rpm for 10 minutes to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 110℃ and the screw speed to 400 rpm. After extrusion, the mixture is cooled to room temperature, and the resulting extrudate is then pulverized. The anti-corrosion synergistic filler is uniformly dispersed in the modified epoxy resin, and the two are tightly bonded together. With the synergy of other additives, a uniform, dense, and multi-layered anti-corrosion powder coating system is constructed, which significantly improves the adhesion and anti-corrosion properties of the coating and extends the service life of the coating, thus obtaining an anti-corrosion steel pipe powder coating.

[0034] Example 2

[0035] This embodiment proposes an anti-corrosion steel pipe powder coating, comprising the following components in parts by weight: 10 parts of anti-corrosion and enhancing filler, 60 parts of modified epoxy resin, 3 parts of dicyandiamide curing agent, 1 part of leveling agent, and 0.4 parts of 2-methylimidazole accelerator.

[0036] The corrosion-resistant and enhanced filler is made from the following components in parts by weight: 10 parts of polypyrrole-coated graphene composite powder, 8 parts of pyrrole, 8 parts of γ-aminopropyltriethoxysilane, 1.0 part of benzotriazole, and 18 parts of ammonium persulfate.

[0037] The modified epoxy resin comprises the following components in parts by weight: 80 parts of bisphenol A type epoxy resin, 10 parts of phenolic epoxy resin, 8 parts of polypropylene glycol diglycidyl ether, 50 parts of octadecanoic acid, and 5 parts of gallic acid.

[0038] The preparation method of corrosion-resistant and corrosion-enhancing fillers specifically includes the following steps:

[0039] (1) Stir 0.6g of hexadecyltrimethylammonium bromide and 25mL of deionized water magnetically for 20min, then slowly add fluorinated graphene. The amount of fluorinated graphene added is 0.5g. Fluorinated graphene has a hydrophobic surface, which reduces water permeability and delays the invasion of corrosive media from the source. The CF bond of fluorinated graphene is very stable. It is resistant to acid, alkali and solvent, providing an extremely stable and durable physicochemical barrier. Fluorinated graphene is also an insulator, which completely avoids the risk of forming an electric couple with the steel substrate at the coating defect and accelerating metal corrosion. Continue to stir magnetically for 20min, then perform ultrasonic dispersion treatment for 30min, centrifuge at 600rpm for 5min, collect the supernatant to obtain dispersion I, then add 0.5g of pyrrole to 30mL of 50% ethanol solution, and sonicate for 20min to obtain solution II. Dissolve 1.8g of anhydrous ferric chloride in 2 0 mL of deionized water was ultrasonically treated for 20 min to obtain solution III. Then, under 0℃ ice bath conditions, dispersion I and solution II were mixed and stirred evenly before adding solution III dropwise. After the addition was completed, the mixture was stirred for 12 h, centrifuged, and the solid product was collected and washed with deionized water until the pH reached 7.0. After drying, polypyrrole was coated on the surface and edges of fluorinated graphene sheets through in-situ polymerization, forming a continuous, dense and uniform coating layer. This not only enhanced the labyrinth effect of fluorinated graphene and prolonged the path and time for corrosive media such as water, oxygen, and chloride ions to diffuse to the surface of the steel pipe, but also improved the wettability and dispersibility of fluorinated graphene and reduced stacking and agglomeration. Among them, the long molecular chains of polypyrrole can entangle and interpenetrate with the molecular chains of epoxy resin to form a strong physical bond, which is conducive to forming a strong and tough interfacial bond and reducing the risk of peeling. The resulting composite powder of polypyrrole-coated graphene was obtained.

[0040] (2) Disperse the polypyrrole-coated graphene composite powder obtained in step (1) in 50 mL of deionized water and ultrasonically disperse for 2 h to obtain a polypyrrole-coated graphene dispersion solution for later use. Then add 0.8 g of pyrrole to 150 mL of 50% ethanol solution and stir for 20 min. Next, add γ-aminopropyltriethoxysilane and benzotriazole. The amount of γ-aminopropyltriethoxysilane and benzotriazole added is 0.8 mL and 0.10 g, respectively. γ-aminopropyltriethoxysilane can prevent corrosion. The medium penetrates along the filler-resin interface or coating-metal interface, enhancing the interfacial corrosion resistance. When the corrosive medium penetrates the coating and comes into contact with the steel pipe surface, benzotriazole rapidly migrates to the metal surface and undergoes chemical adsorption, forming a dense monomolecular protective film. This effectively inhibits corrosion current, prevents corrosion from spreading at the damage site, and endows the damage with self-repairing capabilities. After stirring for 30 minutes, it is added to the polypyrrole-coated graphene dispersion solution, followed by the slow addition of ammonium persulfate solution at 1000 rpm. The mixture is then kept at 0°C. The reaction was carried out in a water bath for 10 hours. The ammonium persulfate solution was prepared by dissolving 1.8 g of ammonium persulfate in 10 mL of deionized water. After the reaction, the mixture was filtered, washed, and the precipitate was dried and pulverized. In this process, polypyrrole-coated graphene composite powder serves as the core. γ-aminopropyltriethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer. The polypyrrole layer generated by secondary polymerization acts as the outermost layer, firmly anchoring and embedding the intermediate layer. γ-aminopropyltriethoxysilane... The chemical bonding and the physical bonding formed by the entanglement and interpenetration of the outer polypyrrole molecular chains exhibit excellent and stable dispersibility. At the same time, the amino groups of γ-aminopropyltriethoxysilane can not only bridge the filler and epoxy resin, but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, thereby improving adhesion. Furthermore, the coating with excellent compatibility, dispersibility and adhesion can maximize the effect of multiple physical barriers, effectively block the penetration of corrosive media, greatly improve the anti-corrosion performance, and obtain an anti-corrosion and enhanced filler.

[0041] This embodiment provides a method for preparing anti-corrosion steel pipe powder coating, specifically including the following steps:

[0042] S1. Add 8.0g of bisphenol A epoxy resin, 1.0g of phenolic epoxy resin, 0.8g of polypropylene glycol diglycidyl ether, 5.0g of octadecanoic acid, and 0.5g of gallic acid sequentially to the reactor. The bisphenol A epoxy resin is type E-20, and the phenolic epoxy resin is type F51. E-20 forms the main framework of the resin system, providing integrity, mechanical strength, and basic adhesion. F51 is a performance enhancer, acting like reinforcing bars within the E-20 framework, improving the resin's corrosion resistance and mechanical strength. The combination of these two components maintains superior corrosion and heat resistance while ensuring good processability and a certain degree of toughness, avoiding brittleness issues. Nitrogen gas is then introduced to displace the air in the reactor. The temperature is raised to 90℃ and stirred for 20 minutes. Then, 0.01g of triphenylphosphine is added, and the temperature is raised to 120℃ and maintained at this temperature. The reaction was continued until the acid value was <5 mg KOH / g, at which point the reaction was stopped and cooled. The mixed epoxy resin was chemically modified by octadecanoic acid and gallic acid to generate an epoxy ester resin with flexible long chains and phenolic hydroxyl groups. The flexible long chains introduced by octadecanoic acid not only disrupted the regularity of the epoxy resin molecular chains and reduced the intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also improved the flexibility. The internal stress generated when the coating is cured and cooled or subjected to external impact can be effectively absorbed and released by the flexible chain segments, improving the adhesion and avoiding the coating from becoming brittle, cracking or peeling off due to excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of metal substrates, generating strong physical adsorption and enhancing the interfacial bonding force, thus obtaining the modified epoxy resin.

[0043] S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at 800 rpm for 5 minutes to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 100℃ and the screw speed to 200 rpm. After extrusion, the mixture is cooled to room temperature, and the resulting extrudate is then pulverized. The anti-corrosion synergistic filler is uniformly dispersed in the modified epoxy resin, and the two are tightly bonded together. With the synergy of other additives, a uniform, dense, and multi-layered anti-corrosion powder coating system is constructed, which significantly improves the adhesion and anti-corrosion properties of the coating and extends the service life of the coating, thus obtaining an anti-corrosion steel pipe powder coating.

[0044] Example 3

[0045] This embodiment proposes an anti-corrosion steel pipe powder coating, comprising the following components in parts by weight: 15 parts of anti-corrosion and enhancing filler, 70 parts of modified epoxy resin, 4 parts of dicyandiamide curing agent, 2 parts of leveling agent, and 0.6 parts of 2-methylimidazole accelerator.

[0046] The corrosion-resistant and enhanced filler is made from the following components in parts by weight: 15 parts of polypyrrole-coated graphene composite powder, 9 parts of pyrrole, 9 parts of γ-aminopropyltriethoxysilane, 1.25 parts of benzotriazole, and 20 parts of ammonium persulfate.

[0047] The modified epoxy resin comprises the following components in parts by weight: 90 parts of bisphenol A type epoxy resin, 15 parts of phenolic epoxy resin, 9 parts of polypropylene glycol diglycidyl ether, 55 parts of octadecanoic acid, and 7.5 parts of gallic acid.

[0048] The preparation method of corrosion-resistant and corrosion-enhancing fillers specifically includes the following steps:

[0049] (1) Stir 0.7g of hexadecyltrimethylammonium bromide and 25mL of deionized water magnetically for 25min, then slowly add fluorinated graphene. The amount of fluorinated graphene added is 0.75g. Fluorinated graphene has a hydrophobic surface, which reduces water permeability and delays the intrusion of corrosive media from the source. The CF bond of fluorinated graphene is very stable. It is resistant to acid, alkali and solvent, providing an extremely stable and durable physicochemical barrier. Fluorinated graphene is also an insulator, which completely avoids the risk of forming an electric couple with the steel substrate at the coating defect and accelerating metal corrosion. Continue to stir magnetically for 25min, then perform ultrasonic dispersion treatment for 35min, centrifuge at 700rpm for 7.5min, collect the supernatant to obtain dispersion I, then add 1.0g of pyrrole to 30mL of 50% ethanol solution, and sonicate for 25min to obtain solution II. Dissolve 2.4g of anhydrous ferric chloride in 20 mL of deionized water was used to sonicate for 25 min to obtain solution III. Then, under ice bath conditions at 2.5 °C, dispersion I and solution II were mixed and stirred evenly before adding solution III dropwise. After the addition was complete, the mixture was stirred for 18 h, centrifuged, and the solid product was collected and washed with deionized water until the pH reached 7.0. After drying, polypyrrole was found to be coated on the surface and edges of fluorinated graphene sheets through in-situ polymerization, forming a continuous, dense, and uniform coating layer. This not only enhanced the labyrinth effect of fluorinated graphene and prolonged the path and time for corrosive media such as water, oxygen, and chloride ions to diffuse to the surface of the steel pipe, but also improved the wettability and dispersibility of fluorinated graphene, reducing stacking and agglomeration. In particular, the long molecular chains of polypyrrole can entangle and interpenetrate with the molecular chains of epoxy resin to form a strong physical bond, which is conducive to forming a strong and tough interfacial bond and reducing the risk of peeling. The resulting composite powder of polypyrrole-coated graphene was obtained.

[0050] (2) The polypyrrole-coated graphene composite powder described in step (1) is dispersed in 50 mL of deionized water and ultrasonically dispersed for 2.5 h to obtain a polypyrrole-coated graphene dispersion solution for later use. Then, 0.9 g of pyrrole is added to 150 mL of 50% ethanol solution and stirred for 25 min. Next, γ-aminopropyltriethoxysilane and benzotriazole are added. The amounts of γ-aminopropyltriethoxysilane and benzotriazole added are 0.9 mL and 0.125 g, respectively. γ-aminopropyltriethoxysilane can prevent... Corrosive media penetrate along the filler-resin interface or coating-metal interface, enhancing the interfacial corrosion resistance. When corrosive media penetrates the coating and comes into contact with the steel pipe surface, benzotriazole rapidly migrates to the metal surface and undergoes chemical adsorption, forming a dense monomolecular protective film. This effectively inhibits corrosion current, prevents corrosion from spreading at the damage site, and endows the damage with self-repairing capabilities. After stirring for 35 minutes, it is added to the polypyrrole-coated graphene dispersion solution, and then ammonium persulfate solution is slowly added at 1500 rpm. The reaction was carried out in an ice-water bath at 5℃ for 11 hours. The ammonium persulfate solution was prepared by dissolving 2.0 g of ammonium persulfate in 15 mL of deionized water. After the reaction, the mixture was filtered, washed, and the precipitate was dried and pulverized. In this process, polypyrrole-coated graphene composite powder serves as the core. γ-aminopropyltriethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer. The polypyrrole layer generated by secondary polymerization acts as the outermost layer, firmly anchoring and embedding the intermediate layer within it. γ-aminopropyltriethoxysilane... The chemical bonding and physical bonding formed by the entanglement and interpenetration of the outer polypyrrole molecular chains exhibit excellent and stable dispersibility. At the same time, the amino groups of γ-aminopropyltriethoxysilane can not only bridge the filler and epoxy resin, but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, thereby improving adhesion. Furthermore, the coating with excellent compatibility, dispersibility and adhesion can maximize the effect of multiple physical barriers, effectively block the penetration of corrosive media, greatly improve the anti-corrosion performance, and obtain an anti-corrosion and enhanced filler.

[0051] This embodiment provides a method for preparing anti-corrosion steel pipe powder coating, specifically including the following steps:

[0052] S1. 9.0g of bisphenol A epoxy resin, 1.5g of phenolic epoxy resin, 0.9g of polypropylene glycol diglycidyl ether, 5.5g of octadecanoic acid, and 0.75g of gallic acid were sequentially added to the reactor. The bisphenol A epoxy resin was type E-20, and the phenolic epoxy resin was type F51. E-20 forms the main framework of the resin system, providing integrity, mechanical strength, and basic adhesion. F51 acts as a performance enhancer, acting like reinforcing bars within the E-20 framework, improving the resin's corrosion resistance and mechanical strength. This combination maintains superior corrosion and heat resistance while ensuring good processability and a certain degree of toughness, avoiding brittleness issues. Nitrogen gas was introduced to displace the air in the reactor. The mixture was heated to 92.5℃ and stirred for 25 minutes. Then, 0.01g of triphenylphosphine was added, and the temperature was raised to 130℃. The mixture was kept at this temperature. The reaction was continuously stirred until the acid value was <5mgKOH / g, at which point the reaction was stopped and cooled. The mixed epoxy resin was chemically modified by octadecanoic acid and gallic acid to generate an epoxy ester resin with flexible long chains and phenolic hydroxyl groups. The flexible long chains introduced by octadecanoic acid not only disrupted the regularity of the epoxy resin molecular chain and reduced the intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also improved the flexibility. The internal stress generated when the coating is cured and cooled or subjected to external impact can be effectively absorbed and released by the flexible chain segments, improving the adhesion and avoiding the coating from becoming brittle, cracking or peeling off due to excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of the metal substrate, generating strong physical adsorption and enhancing the interfacial bonding force, thus obtaining the modified epoxy resin.

[0053] S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at 1000 rpm for 7.5 min to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 105℃ and the screw speed to 300 rpm. After extrusion, the mixture is cooled to room temperature, and the resulting extrudate is then pulverized. The anti-corrosion synergistic filler is uniformly dispersed in the modified epoxy resin, and the two are tightly bonded together. With the synergy of other additives, a uniform, dense, and multi-layered anti-corrosion powder coating system is constructed, which significantly improves the adhesion and anti-corrosion properties of the coating and extends the service life of the coating, thus obtaining an anti-corrosion steel pipe powder coating.

[0054] Example 4

[0055] This embodiment proposes an anti-corrosion steel pipe powder coating, comprising the following components in parts by weight: 20 parts of anti-corrosion and enhancing filler, 60 parts of modified epoxy resin, 5 parts of dicyandiamide curing agent, 3 parts of leveling agent, and 0.8 parts of 2-methylimidazole accelerator.

[0056] The corrosion-resistant and enhanced filler is made from the following components in parts by weight: 20 parts of polypyrrole-coated graphene composite powder, 10 parts of pyrrole, 8 parts of γ-aminopropyltriethoxysilane, 1.0 part of benzotriazole, and 22 parts of ammonium persulfate.

[0057] The modified epoxy resin comprises the following components in parts by weight: 100 parts of bisphenol A type epoxy resin, 10 parts of phenolic epoxy resin, 10 parts of polypropylene glycol diglycidyl ether, 50 parts of octadecanoic acid, and 5 parts of gallic acid.

[0058] The preparation method of corrosion-resistant and corrosion-enhancing fillers specifically includes the following steps:

[0059] (1) Stir 0.8g of hexadecyltrimethylammonium bromide and 25mL of deionized water magnetically for 30min, then slowly add fluorinated graphene. The amount of fluorinated graphene added is 1.0g. Fluorinated graphene has a hydrophobic surface, which reduces water permeability and delays the intrusion of corrosive media from the source. The CF bond of fluorinated graphene is very stable. It is resistant to acid, alkali and solvent, providing an extremely stable and durable physicochemical barrier. Fluorinated graphene is also an insulator, which completely avoids the risk of forming an electric couple with the steel substrate at the coating defect and accelerating metal corrosion. Continue stirring magnetically for 30min, then perform ultrasonic dispersion treatment for 40min, centrifuge at 800rpm for 10min, collect the supernatant to obtain dispersion I, then add 0.5g of pyrrole to 30mL of 50% ethanol solution, and sonicate for 30min to obtain solution II. Dissolve 3.0g of anhydrous ferric chloride in 20 mL of deionized water was used to sonicate for 30 min to obtain solution III. Then, under an ice bath at 5 °C, dispersion I and solution II were mixed and stirred evenly before adding solution III dropwise. After the addition was complete, the mixture was stirred for 24 h, centrifuged, and the solid product was collected and washed with deionized water until the pH reached 7.0. After drying, polypyrrole was found to be coated on the surface and edges of fluorinated graphene sheets through in-situ polymerization, forming a continuous, dense, and uniform coating layer. This not only enhanced the labyrinth effect of fluorinated graphene and prolonged the path and time for corrosive media such as water, oxygen, and chloride ions to diffuse to the surface of the steel pipe, but also improved the wettability and dispersibility of fluorinated graphene, reducing stacking and agglomeration. In particular, the long molecular chains of polypyrrole can entangle and interpenetrate with the molecular chains of epoxy resin to form a strong physical bond, which is conducive to forming a strong and tough interfacial bond and reducing the risk of peeling. The resulting composite powder of polypyrrole-coated graphene was obtained.

[0060] (2) Disperse the polypyrrole-coated graphene composite powder obtained in step (1) in 50 mL of deionized water and ultrasonically disperse it for 3 h to obtain a polypyrrole-coated graphene dispersion solution for later use. Then add 1.0 g of pyrrole to 150 mL of 50% ethanol solution and stir for 30 min. Next, add γ-aminopropyltriethoxysilane and benzotriazole. The amount of γ-aminopropyltriethoxysilane and benzotriazole added is 0.8 mL and 0.10 g, respectively. γ-aminopropyltriethoxysilane can prevent corrosion. The medium penetrates along the filler-resin interface or coating-metal interface, enhancing the interfacial corrosion resistance. When the corrosive medium penetrates the coating and comes into contact with the steel pipe surface, benzotriazole rapidly migrates to the metal surface and undergoes chemical adsorption, forming a dense monomolecular protective film. This effectively inhibits corrosion current, prevents corrosion from spreading at the damage site, and endows the damage with self-repairing capabilities. After stirring for 40 minutes, it is added to the polypyrrole-coated graphene dispersion solution, followed by the slow addition of ammonium persulfate solution at 2000 rpm, and then heated to 5°C. The reaction was carried out in a water bath for 12 hours. The ammonium persulfate solution was prepared by dissolving 2.2 g of ammonium persulfate in 20 mL of deionized water. After the reaction, the mixture was filtered, washed, and the precipitate was dried and pulverized. In this process, polypyrrole-coated graphene composite powder serves as the core. γ-aminopropyltriethoxysilane and benzotriazole are adsorbed on the surface of the polypyrrole-coated graphene composite powder to form an intermediate layer. The polypyrrole layer generated by secondary polymerization acts as the outermost layer, firmly anchoring and embedding the intermediate layer. γ-aminopropyltriethoxysilane... The chemical bonding and the physical bonding formed by the entanglement and interpenetration of the outer polypyrrole molecular chains exhibit excellent and stable dispersibility. At the same time, the amino groups of γ-aminopropyltriethoxysilane can not only bridge the filler and epoxy resin, but also form hydrogen bonds or chemical bonds with the hydroxyl groups on the surface of the metal substrate, thereby improving adhesion. Furthermore, the coating with excellent compatibility, dispersibility and adhesion can maximize the effect of multiple physical barriers, effectively block the penetration of corrosive media, greatly improve the anti-corrosion performance, and obtain an anti-corrosion and enhanced filler.

[0061] This embodiment provides a method for preparing anti-corrosion steel pipe powder coating, specifically including the following steps:

[0062] S1. Add 10.0g of bisphenol A epoxy resin, 1.0g of phenolic epoxy resin, 1.0g of polypropylene glycol diglycidyl ether, 5.0g of octadecanoic acid, and 0.5g of gallic acid sequentially to the reactor. The bisphenol A epoxy resin is type E-20, and the phenolic epoxy resin is type F51. E-20 forms the main framework of the resin system, providing integrity, mechanical strength, and basic adhesion. F51 is a performance enhancer, acting like reinforcing bars within the E-20 framework, improving the resin's corrosion resistance and mechanical strength. The combination of these two components maintains superior corrosion and heat resistance while ensuring good processability and a certain degree of toughness, avoiding brittleness issues. Nitrogen gas is then introduced to displace the air in the reactor. The temperature is raised to 95℃ and stirred for 30 minutes. Then, 0.01g of triphenylphosphine is added, and the temperature is raised to 140℃ and maintained at this temperature. The reaction was continued until the acid value was <5 mg KOH / g, at which point the reaction was stopped and cooled. The mixed epoxy resin was chemically modified by octadecanoic acid and gallic acid to generate an epoxy ester resin with flexible long chains and phenolic hydroxyl groups. The flexible long chains introduced by octadecanoic acid not only disrupted the regularity of the epoxy resin molecular chains and reduced the intermolecular forces, making it easier to wet and disperse fillers during powder coating extrusion, but also improved the flexibility. The internal stress generated when the coating is cured and cooled or subjected to external impact can be effectively absorbed and released by the flexible chain segments, improving the adhesion and avoiding the coating from becoming brittle, cracking or peeling off due to excessive internal stress. The phenolic hydroxyl groups introduced by gallic acid can form extremely strong hydrogen bonds and van der Waals forces with oxides or hydroxyl groups on the surface of metal substrates, generating strong physical adsorption and enhancing the interfacial bonding force, thus obtaining the modified epoxy resin.

[0063] S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at 1200 rpm for 10 minutes to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 110℃ and the screw speed to 400 rpm. After extrusion, the mixture is cooled to room temperature, and the resulting extrudate is then pulverized. The anti-corrosion synergistic filler is uniformly dispersed in the modified epoxy resin, and the two are tightly bonded together. With the synergy of other additives, a uniform, dense, and multi-layered anti-corrosion powder coating system is constructed, which significantly improves the adhesion and anti-corrosion properties of the coating and extends the service life of the coating, thus obtaining an anti-corrosion steel pipe powder coating.

[0064] Comparative Example 1

[0065] This comparative example provides a powder coating for anti-corrosion steel pipes. The difference between this example and Example 1 is that the composite powder of polypyrrole-coated graphene does not contain pyrrole, and fluorinated graphene is replaced with graphene; the preparation method of the anti-corrosion and enhancing filler step (1) does not include solution II, and fluorinated graphene is replaced with graphene; the preparation method of the powder coating for anti-corrosion steel pipes is the same as that of Example 1.

[0066] Comparative Example 2

[0067] This comparative example provides a powder coating for anti-corrosion steel pipes, which differs from Example 1 in that the anti-corrosion enhancing filler does not contain γ-aminopropyltriethoxysilane or benzotriazole; γ-aminopropyltriethoxysilane and benzotriazole are not added in step (2) of the preparation method of the anti-corrosion enhancing filler; and the preparation method of the anti-corrosion steel pipe powder coating is the same as that of Example 1.

[0068] Comparative Example 3

[0069] This comparative example provides an anti-corrosion steel pipe powder coating, which differs from Example 1 in that the modified epoxy resin does not contain octadecanoic acid or gallic acid; the preparation method of the anti-corrosion and enhancing filler is the same as in Example 1; and octadecanoic acid and gallic acid are not added in step S1 of the preparation method of the anti-corrosion steel pipe powder coating.

[0070] Experimental Example 1

[0071] Adhesion test

[0072] Test samples: anti-corrosion steel pipe powder coatings prepared in Examples 1-4 and Comparative Examples 1-3.

[0073] Test method: After the test sample is cured (coating thickness is 80±10μm), it is tested by a pull-out adhesion tester and measured according to ASTM D4541 standard. The pressure system is calibrated by NIST with an accuracy of ±1% (full scale) and the value is accurate to 0.01.

[0074] Figure 1 The figures show the adhesion results for Examples 1-4 and Comparative Examples 1-3. As shown, the adhesion of Examples 1-4 is 13.8-15.7 MPa, indicating good adhesion; the adhesion of Comparative Examples 1-3 is 6.2-11.5 MPa, indicating average or poor adhesion. The polypyrrole-coated graphene composite powder in Comparative Example 1 does not contain pyrrole and replaces fluorinated graphene with graphene. Therefore, the polypyrrole coating cannot improve the dispersibility of graphene, causing graphene agglomeration or stacking, which has an adverse effect on interface defects, resulting in average adhesion. The anti-corrosion and enhancing filler in Comparative Example 2 does not contain γ-aminopropyltriethoxysilane or benzotriazole, so it cannot form chemical anchoring points between the filler, resin, and metal substrate through the chemical bonding of γ-aminopropyltriethoxysilane, resulting in poor adhesion. The modified epoxy resin in Comparative Example 3 does not contain octadecanoic acid or gallic acid, so it cannot introduce flexible long chains and phenolic hydroxyl groups to modify the epoxy resin. This means it cannot reduce the intermolecular forces of the resin, which is not conducive to filler dispersion, nor can it enhance the interfacial bonding force through phenolic hydroxyl groups, resulting in poor adhesion.

[0075] Experiment Example 2

[0076] Corrosion resistance test

[0077] Test samples: anti-corrosion steel pipe powder coatings prepared in Examples 1-4 and Comparative Examples 1-3.

[0078] Test method: According to the national standard GB / T1771-2007, the test sample was sprayed onto a 440C martensitic stainless steel substrate and an X-shaped mark was made to the substrate. After curing, the coating thickness was 80±10μm. Then, it was placed in a salt spray chamber at a temperature of 35±2℃ and a salt spray solution deposition rate of 1.5±0.5mL / h. A 5% NaCl solution (pH 6.5-7.2) was used to conduct a salt spray resistance test for 500h. After the test, the rust was peeled off along the X-mark, and the length of the maximum corrosion on the substrate was measured and recorded as the maximum corrosion length (mm). The smaller the maximum corrosion length, the stronger the corrosion resistance.

[0079] Figure 2 The figures show the maximum corrosion length results for Examples 1-4 and Comparative Examples 1-3. As shown, the maximum corrosion length for Examples 1-4 is 0.4-0.8 mm, indicating good corrosion resistance. The maximum corrosion length for Comparative Examples 1-3 is 1.4-3.6 mm, indicating average or poor corrosion resistance. The polypyrrole-coated graphene composite powder in Comparative Example 1 does not contain pyrrole, and replacing fluorinated graphene with graphene fails to improve the risk of graphene agglomeration, forming agglomerates and defect channels through which corrosive media preferentially penetrate rapidly. Furthermore, it fails to utilize the insulating properties of fluorinated graphene. Replacing it with graphene... Graphene significantly accelerates galvanic corrosion of metals, resulting in poor corrosion resistance. The corrosion-enhancing filler in Comparative Example 2 does not contain γ-aminopropyltriethoxysilane or benzotriazole, so it cannot improve interfacial compatibility through the chemical bonding of γ-aminopropyltriethoxysilane, which is not conducive to reducing defect channels, nor can it utilize the damage self-healing properties of benzotriazole, which is not conducive to inhibiting corrosion current, resulting in poor corrosion resistance. The modified epoxy resin in Comparative Example 3 does not contain octadecanoic acid or gallic acid, which is not conducive to the dispersibility of fillers and the density of coatings, and has an adverse effect on the physical barrier, resulting in mediocre corrosion resistance.

[0080] The above experimental results show that the adhesion and corrosion resistance of Examples 1-4 of the present invention are significantly better than those of Comparative Examples 1-3. Among them, Example 1, which uses corrosion-enhancing fillers and modified epoxy resin, has better adhesion and stronger corrosion resistance. The corrosion-enhancing fillers are uniformly and stably dispersed in the modified epoxy resin through chemical bonding and physical bonding, which effectively improves the interfacial compatibility and bonding between the two. It not only enhances the corrosion resistance of the powder coating through multiple mechanisms such as dense physical barrier, electrochemical protection and self-healing, but also significantly improves the adhesion, reduces the risk of cracking, breakage and peeling after the powder coating is cured, and extends the service life of the coating.

[0081] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0082] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A powder coating for anti-corrosion steel pipes, characterized in that: The anti-corrosion steel pipe powder coating comprises the following components in parts by weight: 10-20 parts of anti-corrosion enhancing filler, 60-80 parts of modified epoxy resin, 3-5 parts of dicyandiamide curing agent, 1-3 parts of leveling agent, and 0.4-0.8 parts of 2-methylimidazole accelerator; the anti-corrosion enhancing filler is made from the following components in parts by weight: 10-20 parts of polypyrrole-coated fluorinated graphene composite powder, 8-10 parts of pyrrole, 8-10 parts of γ-aminopropyltriethoxysilane, 1.0-1.5 parts of benzotriazole, and 18-22 parts of ammonium persulfate; the modified epoxy resin comprises the following components in parts by weight: 80-100 parts of bisphenol A type epoxy resin, 10-20 parts of phenolic epoxy resin, 8-10 parts of polypropylene glycol diglycidyl ether, 50-60 parts of octadecanoic acid, and 5-10 parts of gallic acid.

2. A method for preparing anti-corrosion steel pipe powder coating according to claim 1, characterized in that: Specifically, the following steps are included: S1. Add 8.0-10.0g of bisphenol A epoxy resin, 1.0-2.0g of phenolic epoxy resin, 0.8-1.0g of polypropylene glycol diglycidyl ether, 5.0-6.0g of octadecanoic acid, and 0.5-1.0g of gallic acid sequentially to a reaction vessel, and purge the air in the reaction vessel with nitrogen gas. Heat to 90-95℃ and stir for 20-30 minutes. Then add 0.01g of triphenylphosphine and heat to 120-140℃. Continue stirring the reaction under the heat preservation condition until the acid value is <5mgKOH / g. Stop the reaction, cool, and obtain the modified epoxy resin. S2. The modified epoxy resin, anti-corrosion synergistic filler, dicyandiamide curing agent, leveling agent, and 2-methylimidazole accelerator described in step S1 are mixed in a high-speed mixer at a speed of 800-1200 rpm for 5-10 minutes to obtain a premix. The premix is ​​then placed in a twin-screw extruder, and the extrusion temperature is set to 100-110℃ and the screw speed to 200-400 rpm. After extrusion, the material is cooled to room temperature, and the resulting extrudate is then pulverized to obtain an anti-corrosion steel pipe powder coating.

3. The method for preparing anti-corrosion steel pipe powder coating according to claim 2, characterized in that: In step S1, the bisphenol A type epoxy resin is type E-20, and the phenolic epoxy resin is type F51.

4. The method for preparing anti-corrosion steel pipe powder coating according to claim 3, characterized in that: The preparation method of the corrosion-resistant and enhanced filler specifically includes the following steps: (1) Stir 0.6-0.8g of cetyltrimethylammonium bromide and 25mL of deionized water magnetically for 20-30min, slowly add fluorinated graphene, continue stirring magnetically for 20-30min, then perform ultrasonic dispersion for 30-40min, centrifuge at 600-800rpm for 5-10min, collect the supernatant to obtain dispersion I, then add 0.5-1.5g of pyrrole to 30mL of 50% ethanol solution, sonicate for 20-30min to obtain solution II, dissolve 1.8-3.0g of anhydrous ferric chloride in 20mL of deionized water, sonicate for 20-30min to obtain solution III, then mix dispersion I and solution II under ice bath conditions at 0-5℃, stir evenly and then add solution III dropwise, stir for 12-24h after the dropwise addition is completed, centrifuge, collect the solid product and wash with deionized water until pH is 7.0, dry to obtain polypyrrole-coated fluorinated graphene composite powder; (2) Disperse the polypyrrole-coated fluorinated graphene composite powder described in step (1) in 50 mL of deionized water and ultrasonically disperse it for 2-3 h to obtain a polypyrrole-coated fluorinated graphene dispersion solution for later use. Then add 0.8-1.0 g of pyrrole to 150 mL of 50% ethanol solution and stir for 20-30 min. Then add γ-aminopropyltriethoxysilane and benzotriazole and continue stirring for 30-40 min. Then add it to the polypyrrole-coated fluorinated graphene dispersion solution. Then slowly add ammonium persulfate solution at 1000-2000 rpm and react in an ice-water bath at 0-5℃ for 10-12 h. The ammonium persulfate solution is prepared by dissolving 1.8-2.2 g of ammonium persulfate in 10-20 mL of deionized water. After the reaction is completed, filter, wash, dry the precipitate, and pulverize to obtain the anti-corrosion and enhanced filler.

5. The method for preparing anti-corrosion steel pipe powder coating according to claim 4, characterized in that: In step (1), the amount of fluorinated graphene added is 0.5-1.0g.

6. The method for preparing anti-corrosion steel pipe powder coating according to claim 5, characterized in that: In step (2), the amounts of γ-aminopropyltriethoxysilane and benzotriazole added are 0.8-1.0 mL and 0.10-0.15 g, respectively.

Images