Epoxy composite anticorrosive paint and preparation method thereof

Abstract

The application discloses an epoxy composite anticorrosive paint and a preparation method thereof, and relates to the technical field of anticorrosive paint processing. The preparation method comprises the following steps in sequence: firstly, a composite precursor is prepared; sodium-based montmorillonite, zinc nitrate and aluminum nitrate are mixed according to a mass ratio of 2:1:2; deionized water is added, a solid-liquid ratio is 1:5; the mixture is placed in a sealed container to perform a constant-temperature sealed hydrothermal reaction; the pH of the system is adjusted to 5.2; after the reaction is completed, the mixture is sequentially subjected to filtration and constant-temperature drying treatment, so that the intercalation blending precursor particles with a bulk density of 0.32 g / cm3 to 0.38 g / cm3 and an interlayer spacing of 1.9 nm are obtained; the paint can be adapted to a deep-sea low-temperature environment, the coating still maintains good flexibility, and there is no phenomenon of brittleness and cracking; the paint has weak alkaline pH response and high-pressure response capacity; the self-assembly mechanism is activated only in a specific deep-sea environment; the stability in the storage process is ensured, the performance is strengthened in the service environment, and the problem of poor environmental adaptability of the existing paint is solved.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating processing technology, specifically an epoxy composite anti-corrosion coating and its preparation method. Background Technology

[0002] The deep-sea environment is characterized by harsh conditions such as high pressure, low temperature, high salinity, and high pH (usually 8.0-8.5). It also presents complex working conditions such as seawater flow and marine organism attachment, which place extremely high demands on the anti-corrosion coatings of metal substrates such as deep-sea pipelines and offshore platforms. Currently, existing epoxy anti-corrosion coatings for deep-sea applications mainly use a single epoxy resin matrix combined with conventional anti-corrosion fillers (such as zinc powder and talc powder). These coatings suffer from the following core defects: First, insufficient anti-corrosion durability. Under the high pressure and high salinity of the deep sea, the coating is prone to penetration and peeling, resulting in a short service life and failing to meet the long-term service requirements of deep-sea equipment. Second, poor environmental adaptability. The coating is prone to embrittlement and cracking under low-temperature conditions, making it unsuitable for the low-temperature working conditions of the deep sea. Furthermore, it lacks pH and pressure response capabilities, and cannot achieve self-repair or performance enhancement based on changes in the deep-sea environment. Third, unreasonable preparation processes lead to uneven filler dispersion, weak adhesion between the coating and the substrate, and the generation of internal stress during curing, further reducing the coating's anti-corrosion performance. Fourth, existing coatings mostly employ a single anti-corrosion mechanism, lacking synergistic effects, making it difficult to resist long-term erosion in the complex corrosive environment of the deep sea.

[0003] To address the shortcomings of existing technologies, there is an urgent need to develop a method for preparing epoxy composite anti-corrosion coatings that are adaptable to the harsh deep-sea environment, have excellent anti-corrosion performance, strong environmental responsiveness, and stable preparation process. This would solve the technical problems of existing coatings, such as rapid peeling rate, easy embrittlement at low temperatures, and lack of environmental responsiveness, and ensure the long-term stable service of deep-sea metal substrates. Summary of the Invention

[0004] The purpose of this invention is to provide an epoxy composite anti-corrosion coating and its preparation method, comprising the following steps performed sequentially:

[0005] First, a composite precursor was prepared by mixing sodium montmorillonite, zinc nitrate, and aluminum nitrate in a mass ratio of 2:1:2, adding deionized water, and placing the mixture in a sealed container for a constant-temperature, closed-loop hydrothermal reaction. The pH of the system was adjusted to 5.2. After the reaction was completed, the mixture was filtered and dried at a constant temperature to obtain intercalated blend precursor particles with a bulk density of 0.32 g / cm³ to 0.38 g / cm³ and an interlayer spacing of 1.9 nm.

[0006] The above-mentioned intercalated blend precursor particles were subjected to in-situ interfacial coating treatment using melamine urea-formaldehyde copolymer. The temperature, pH value and material ratio of the coating reaction were controlled to obtain a composite precursor.

[0007] To prepare the epoxy resin base material, bisphenol F epoxy resin, polycarboxylic acid ammonium salt dispersant, and polydimethylsiloxane defoamer are added and mixed in sequence until the system is uniform and free of visible particles, thus obtaining the epoxy resin base slurry.

[0008] The above-mentioned composite precursor is added to the epoxy resin matrix slurry in a specific proportion based on the mass of the epoxy resin matrix. This proportion is determined based on the requirements of coating anti-corrosion performance and viscosity balance. The agglomerates are first mixed and dispersed, and then ground until the slurry fineness is less than 20μm to obtain the first component slurry.

[0009] The curing agent component was prepared separately. Methylhexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent were added and mixed in sequence. The mixture was then mixed in a closed and light-proof environment until the system was homogeneous to obtain the second component slurry.

[0010] The first component slurry and the second component slurry were mixed at a mass ratio of 5:1 and continuously mixed in a constant temperature and sealed environment at 28℃. The temperature was controlled to remain stable throughout the process to obtain the finished coating.

[0011] First, the surface of the deep-sea pipeline metal substrate is roughened, and the roughening intensity and angle are controlled to remove the oxide scale and oil stains on the substrate surface. Then, the finished coating is applied to the pretreated substrate surface, and the coating rate and amplitude are controlled to ensure uniform wet film thickness, thus obtaining a wet film coating.

[0012] The coated substrate is placed in a programmable heating environment and cured in three stages at a heating rate of 1.2℃ / min.

[0013] The cured substrate is placed in a constant temperature and humidity environment for static curing to release internal stress and stabilize performance, resulting in a finished anti-corrosion coating.

[0014] The technical solution of the present invention brings at least the following beneficial effects:

[0015] By preparing intercalated blended precursors and performing in-situ interface coating treatment, the coating can achieve precursor self-assembly in the deep-sea environment, forming a continuous and dense barrier layer that effectively blocks the penetration of corrosive media such as seawater and salt, and significantly reduces the coating peeling rate.

[0016] It can adapt to the low temperature environment of the deep sea, and the coating still maintains good flexibility without embrittlement or cracking. It also has weak alkaline pH response and high pressure response capabilities, and activates the self-assembly mechanism only in the specific environment of the deep sea. This ensures stability during storage and enhances performance in the service environment, solving the problem of poor environmental adaptability of existing coatings. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0019] Please see Figure 1 This application provides an epoxy composite anti-corrosion coating and its preparation method, comprising the following steps performed sequentially:

[0020] First, a composite precursor was prepared by mixing sodium montmorillonite, zinc nitrate, and aluminum nitrate in a mass ratio of 2:1:2, adding deionized water, and placing the mixture in a sealed container for a constant-temperature, closed-loop hydrothermal reaction. The pH of the system was adjusted to 5.2. After the reaction was completed, the mixture was filtered and dried at a constant temperature to obtain intercalated blend precursor particles with a bulk density of 0.32 g / cm³ to 0.38 g / cm³ and an interlayer spacing of 1.9 nm.

[0021] The above-mentioned intercalated blend precursor particles were subjected to in-situ interfacial coating treatment using melamine urea-formaldehyde copolymer. The temperature, pH value and material ratio of the coating reaction were controlled to obtain a composite precursor.

[0022] To prepare the epoxy resin base material, bisphenol F epoxy resin, polycarboxylic acid ammonium salt dispersant, and polydimethylsiloxane defoamer are added and mixed in sequence until the system is uniform and free of visible particles, thus obtaining the epoxy resin base slurry.

[0023] The above-mentioned composite precursor is added to the epoxy resin matrix slurry in a specific proportion based on the mass of the epoxy resin matrix. This proportion is determined based on the requirements of coating anti-corrosion performance and viscosity balance. The agglomerates are first mixed and dispersed, and then ground until the slurry fineness is less than 20μm to obtain the first component slurry.

[0024] The curing agent component was prepared separately. Methylhexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent were added and mixed in sequence. The mixture was then mixed in a closed and light-proof environment until the system was homogeneous to obtain the second component slurry.

[0025] The first component slurry and the second component slurry were mixed at a mass ratio of 5:1 and continuously mixed in a constant temperature and sealed environment at 28℃. The temperature was controlled to remain stable throughout the process to obtain the finished coating.

[0026] First, the surface of the deep-sea pipeline metal substrate is roughened, and the roughening intensity and angle are controlled to remove the oxide scale and oil stains on the substrate surface. Then, the finished coating is applied to the pretreated substrate surface, and the coating rate and amplitude are controlled to ensure uniform wet film thickness, thus obtaining a wet film coating.

[0027] The coated substrate is placed in a programmable heating environment and cured in three stages at a heating rate of 1.2℃ / min.

[0028] The cured substrate is placed in a constant temperature and humidity environment for static curing to release internal stress and stabilize performance, resulting in a finished anti-corrosion coating.

[0029] It should be noted that the determination of the solid-liquid ratio of 1:5 is based on precursor particle dispersibility tests. When the solid-liquid ratio is lower than 1:4, the particles are prone to agglomeration, and when it is higher than 1:6, the reaction efficiency decreases significantly. The optimal ratio was obtained through orthogonal experimental calculations. The steps of this method are sequentially linked, with the product of the previous process directly used as the raw material for the next process. Parameters such as temperature, mixing time, and material ratio are matched and work synergistically. During the gradient temperature curing process, the segmented temperatures sequentially trigger the melting of the coating layer, the in-situ activation of the precursor, the ring-opening reaction between the precursor and the epoxy resin, and the cross-linking and curing of the resin. Finally, in the deep-sea environment, pressure and pH value jointly trigger the self-assembly of the precursor to form a continuous barrier layer. Experimental verification shows that when using the coating technology alone, the deep-sea peeling rate is 0.12 mm / d; when using gradient curing alone, the deep-sea peeling rate is 0.11 mm / d; and when using pressure assembly alone, the deep-sea peeling rate is 0.10 mm / d.

[0030] As an optional embodiment, the hydrothermal reaction and post-processing steps for preparing the composite precursor are a linked process: the uniformly mixed powder is mixed with deionized water and placed in a sealed container. After sealing, the temperature is raised to 85°C and continuously stirred at a constant temperature. The pH of the system is adjusted to 5.2 and the reaction is carried out at a constant temperature for 5 hours. After the reaction is completed, the temperature is naturally cooled to room temperature. The solid product is separated by vacuum filtration. The solid product is then placed in a constant temperature drying environment and dried at 105°C for 2 hours. After pulverizing and sieving, intercalated blend precursor particles with a particle size controlled between 2μm and 4μm, a bulk density of 0.32g / cm³ to 0.38g / cm³, and an interlayer spacing of 1.9nm are obtained.

[0031] It should be noted that: the hydrothermal reaction temperature of 85℃ was determined based on the kinetic equation of the sodium-based montmorillonite intercalation reaction. The activation energy of this reaction is 48 kJ / mol. The conversion rate of the intercalation reaction is low below 80℃, and the precursor particles are prone to agglomeration above 90℃. This temperature was determined through kinetic calculations. The reaction time of 5 h was determined based on the reaction rate constant k being equal to 0.21 h / h at 85℃, calculated according to the reaction kinetic formula. The stirring operation was based on the absence of obvious particle agglomeration in the system. This operation method can ensure uniform particle dispersion and avoid energy waste. The particle size of 2 μm to 4 μm was determined based on the grinding slurry. The required fineness of the precursor was determined by controlling the initial particle size within this range, which was then optimized through laser particle size analyzer testing and calculation. The drying temperature of 105℃ and drying time of 2 hours were optimized to meet the drying requirements of the precursor, based on drying effect experiments. pH 5.2 was the optimal condition for the intercalation reaction, allowing zinc and aluminum ions to effectively insert into the interlayer of montmorillonite. An interlayer spacing of 1.9 nm was a crucial prerequisite for pressure-triggered self-assembly, ensuring interlayer sliding under pressure and achieving directional alignment. Particle size was measured using a laser particle size analyzer, bulk density was measured using the tap density method, and interlayer spacing was measured using X-ray diffraction.

[0032] As an optional embodiment, the in-situ interface coating treatment is a closed-loop process: the dried intercalated blend precursor particles are dispersed in anhydrous ethanol system, heated to 65°C and kept at a constant temperature, melamine, urea-formaldehyde monomers and dilute hydrochloric acid catalyst are added according to a preset ratio, the pH of the system is adjusted to 5.0, the molar ratio of formaldehyde to amino is 1.8:1, and the mixture is continuously stirred to carry out the in-situ interface polymerization coating reaction. The reaction is kept at a constant temperature for 2.5 hours. After the reaction is completed, the mixture is cooled, filtered, washed, and dried at low temperature to obtain a fully coated composite precursor. The coating treatment controls the molar ratio of melamine to urea-formaldehyde to be 3.2:1, the coating layer thickness is controlled at 40 nm, and the coating layer melting initiation temperature is 116°C.

[0033] It should be noted that: the melamine to urea-formaldehyde molar ratio of 3.2:1 was determined based on the crosslinking degree requirements of the melamine-urea-formaldehyde copolymer. A molar ratio below 2:1 results in insufficient crosslinking and easy breakage of the coating layer, while a ratio above 4:1 increases the brittleness of the coating layer. This ratio was determined through crosslinking degree testing and calculation. The reaction temperature of 65℃ was determined based on the activation energy of the coating reaction. At this temperature, the reaction rate and crosslinking degree reach equilibrium. Below 60℃, the reaction is incomplete, and above 70℃, bubbles easily appear in the coating layer. This temperature was determined through experimental optimization and calculation. The reaction time of 2.5 hours was determined based on the coating reaction rate at 65℃, calculated through fitting experimental data. At this temperature, the coating layer thickness meets the design requirements. The coating layer thickness of 40nm was determined based on the precursor particle size of 2-4μm. When the coating layer thickness is matched with the precursor particle size, storage stability can be guaranteed, and... The coating rapidly melts at a set temperature, determined through geometric dimension matching calculations. The melting temperature of the coating layer is 116℃, designed based on the second stage of gradient curing temperature, and determined by adjusting the ratio of melamine to urea-formaldehyde through differential scanning calorimetry (DSC). pH=5.0 and a formaldehyde to amino molar ratio of 1.8:1 are the core conditions for the polycondensation reaction, allowing precise control of the coating layer structure and imparting a weakly alkaline response characteristic. The assembly mechanism can only be fully activated in the deep-sea environment at pH=8.2. At 4℃, the coating layer maintains its flexibility with a glass transition temperature of -12℃, and the pressure trigger threshold remains at 10 MPa, unaffected by the low temperatures of the deep sea. The coating layer thickness is measured using transmission electron microscopy, and the coating layer melting initiation temperature is measured using differential scanning calorimetry.

[0034] As an optional embodiment, the first component slurry is prepared by a dispersion process: first, bisphenol F epoxy resin, polycarboxylate ammonium salt dispersant, and polydimethylsiloxane defoamer are added in proportion and mixed until the system is uniform and free of visible particles. The mixture is then continuously mixed for 30 minutes to obtain a uniform base material. Next, the composite precursor is added to the base material in small batches. The mixture is first mixed for 5 minutes to break up the agglomerates, and then ground until the slurry fineness is less than 20 μm to obtain the first component slurry. The amount of composite precursor added is determined based on the requirements of coating anti-corrosion performance and viscosity balance, the amount of dispersant added is determined based on the requirements of first component dispersibility, and the amount of defoamer added is determined based on the requirements of coating defoaming effect and cost balance.

[0035] It should be noted that: the amount of composite precursor added is based on the balance requirements of the coating's anti-corrosion performance and viscosity. If the amount added is too low, the anti-corrosion performance will be insufficient; if the amount added is too high, the coating viscosity will exceed the standard and construction will be difficult. The amount added is determined by calculation through orthogonal experiments combined with range analysis. The amount of dispersant added is based on the dispersibility requirements of the first component. If the amount added is too low, the precursor will be unevenly dispersed; if the amount added is too high, it will affect the coating's curing performance. The amount added is determined by optimization calculation through dispersibility experiments. The amount of defoamer added is based on the balance between the coating's defoaming effect and cost. If the amount added is too low, defoaming will be incomplete; if the amount added is too high, it will easily cause pinhole defects. The amount added is determined by calculation through defoaming experiments. The relevant operating parameters for mixing and grinding are matched with the structure of the precursor coating layer to avoid damaging the integrity of the coating layer during the grinding process.

[0036] As an optional embodiment, the second component slurry is prepared by a mixing process: methyl hexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent are added sequentially in proportion, and mixed for 15 minutes in a sealed, light-proof, constant temperature environment of 25°C. Air is avoided during the mixing process to obtain the second component slurry. The amount of diluent added is determined based on the viscosity requirements of the curing agent component, and the amount of leveling agent added is determined based on the coating leveling effect requirements. After the second component is prepared, it is sealed and allowed to stand for 30 minutes before being mixed with the first component.

[0037] It should be noted that: the amount of diluent added is based on the viscosity requirements of the curing agent components. If the amount added is too low, the viscosity will be too high and it will be difficult to mix. If the amount added is too high, it will affect the curing rate. The amount added is determined by optimization calculation through viscosity testing. The amount of leveling agent added is based on the leveling effect of the coating. If the amount added is too low, the leveling performance will be poor. If the amount added is too high, it will easily cause sagging defects. The amount added is determined by calculation through leveling performance testing. The mixing operation is based on the standard of uniform system without layering. This operation method can ensure uniform mixing of components and avoid the generation of air bubbles. The mixing time of 15 minutes is determined by calculation based on experimental data fitting.

[0038] As an optional embodiment, the two-component mixing is a closed-loop process: the second component, after being allowed to stand, is slowly poured into the first component slurry in several batches, and the entire process is carried out in a constant temperature and sealed environment at 28°C for 20 minutes. The mixing process is sealed and protected from light to avoid temperature fluctuations. After mixing, the mixture is filtered under pressure using a 120-mesh stainless steel filter to remove impurities and undispersed agglomerates, resulting in the finished coating. The mass ratio of the first component to the second component is controlled at 5:1. The pot life of the mixed system is 4 hours.

[0039] It should be noted that: the constant temperature mixing temperature is 28℃, based on the reactivity of epoxy resin and curing agent. The viscosity of the mixture is higher below 25℃, and premature curing is likely to occur above 30℃. This was determined through viscosity and curing rate testing and calculation. The mixing time is 20 minutes, determined through mixing rate testing and calculation based on the mixing uniformity at this temperature. The mass ratio of the two components is 5:1, based on the stoichiometric ratio of the epoxy value of the epoxy resin to the amine value of the curing agent. This ratio was determined through stoichiometric calculation when the epoxy value is 0.45 and the amine value is 300, ensuring complete curing. The pot life is 4 hours, derived from the rate of curing reaction at room temperature, ensuring sufficient construction time after mixing while avoiding premature curing.

[0040] As an optional embodiment, the substrate pretreatment and spraying process is a standardized process: the substrate pretreatment adopts a high-pressure dry roughening process, using 0.8mm particle size quartz sand, controlling the roughening intensity, and controlling the roughening angle at 75°-80°. The roughening position is moved at a constant speed throughout the process. After treatment, the substrate surface is free of oxide scale, oil stains, and dust, and the surface roughness is controlled at Ra4.5μm. The coating process is completed within 30 minutes after the pretreatment, controlling the coating rate and coating amplitude to ensure uniform wet film thickness. The coating direction is kept perpendicular to the substrate surface, and the coating position is moved at a constant speed. The wet film thickness is controlled at 150μm, and the coating is completed in a single coat.

[0041] It should be noted that: the quartz sand particle size is 0.8mm, based on the surface roughness requirements of the substrate. A particle size smaller than 0.5mm results in insufficient roughness, while a particle size larger than 1.0mm easily causes scratches on the substrate surface. This was determined through roughness testing and optimization calculations. The control standard for roughening intensity is based on a balance between roughening efficiency and substrate damage. Too low an intensity results in incomplete roughening, while too high an intensity damages the substrate surface. This was determined through roughening effect testing and calculations. The substrate surface roughness Ra is 4.5μm, based on the coating adhesion requirements. A roughness lower than Ra 3.2μm is considered acceptable. Insufficient adhesion, exceeding Ra 6.3μm, easily leads to stress concentration in the coating, determined through adhesion testing and calculation; the control standard for coating rate and amplitude, based on coating efficiency and coating thickness uniformity requirements, avoids excessive coating thickness causing sagging or excessive thinness affecting the anti-corrosion effect, determined through coating test calculation; wet film thickness of 150μm, based on deep-sea anti-corrosion requirements, indicates insufficient dry film thickness when wet film thickness is below 120μm, and easy cracking when wet film thickness is above 180μm, determined through dry film thickness conversion calculation; surface roughness is tested using a stylus profilometer.

[0042] As an optional embodiment, the three-stage gradient heating and curing is a sequentially triggered process, with the heating rate controlled at 1.2℃ / min throughout the process, without drastic temperature fluctuations. The specific segmented process is as follows: the first stage is heated to 65℃ and held at a constant temperature for 25 minutes; the second stage is heated to 116℃ and held at a constant temperature for 50 minutes; and the third stage is heated to 155℃ and held at a constant temperature for 35 minutes.

[0043] It should be noted that: the first stage temperature is 65℃ and the holding time is 25min. Based on the coating leveling requirements, leveling is insufficient below 60℃, and the solvent evaporates too quickly above 70℃, easily causing pinholes. The holding time was determined by calculation based on leveling effect test. The second stage temperature is 116℃ and the holding time is 50min. Based on the requirements of coating melting and initial reaction of precursor, this temperature matches the coating melting temperature and was determined by reaction kinetic calculation. At this time, the coating can completely melt. The third stage temperature is 155℃ and the holding time is 35min. Based on the requirements of epoxy resin crosslinking and precursor ring-opening reaction, curing is incomplete below 150℃, and the resin is easily degraded above 160℃. The temperature was determined by calculation based on curing degree test. The heating rate is 1.2℃ / min. Based on coating internal stress control, the efficiency is too low below 1℃ / min, and the coating is prone to internal stress cracking above 1.5℃ / min. The temperature was determined by calculation based on internal stress test.

[0044] As an optional embodiment, the post-curing maintenance is a closed-loop process: the cured coating substrate is placed in a constant temperature and humidity environment, and under the conditions of ambient temperature of 23°C and relative humidity of 50%, it is sealed and left to cure for 84 hours. During the curing process, direct sunlight, dust pollution, and external impacts are avoided, and the substrate is not moved throughout the process.

[0045] It should be noted that: the curing temperature is 23℃, based on the requirement for stable coating performance after curing. The curing rate is slow when the temperature is below 20℃, and the coating is prone to aging when the temperature is above 25℃. This was determined by calculation based on curing effect test. The relative humidity is 50%, based on the requirement for water absorption performance of the coating. The coating is prone to cracking when the humidity is below 40%, and prone to dampness when the humidity is above 60%. This was determined by calculation based on water absorption rate test. The curing time is 84h, based on the curing rate at 23℃ and 50% humidity. At this time, the coating performance can reach a stable value. This was determined by calculation based on coating performance test.

[0046] As an optional embodiment, during the curing process, a sealed protective method is used for full wrapping protection. The substrate is placed horizontally, maintaining a distance of 10-15cm from the bottom surface of the curing environment. The temperature fluctuation of the curing environment is controlled within ±1℃, and the relative humidity fluctuation is controlled within ±2%. Temperature and humidity are monitored in real time throughout the process, and the temperature and humidity data are recorded every 30 minutes. If the temperature and humidity exceed the set range, the temperature and humidity are immediately adjusted and restored to the set values ​​within 10 minutes. In the later 48 hours of curing, the coating surface is wiped daily with a dust-free soft cloth, taking care not to damage the coating surface, to remove the trace dust adhering to the surface.

[0047] It should be noted that: the sealed, fully enclosed protective design, based on the surface precision requirements of deep-sea coatings, can reduce direct contact between dust and moisture and the coating. This design parameter was determined through coating surface defect rate testing; the substrate placement spacing of 10-15cm was determined through fluid dynamics calculations, which ensures uniform temperature and humidity distribution within the curing environment; the temperature and humidity fluctuation range of ±1℃ and ±2% was determined through coating performance stability testing, which ensures the stability of the coating's cross-linking structure; the wiping operation time and method were optimized through coating surface roughness testing and calculations, using a dust-free soft cloth that does not damage the coating, which can improve surface smoothness without damaging the coating.

[0048] The preparation method of the present invention will be described in detail below through three specific embodiments.

[0049] Example 1

[0050] A method for preparing an epoxy composite anti-corrosion coating for deep-sea applications includes the following steps:

[0051] Preparation of composite precursor: Sodium-based montmorillonite, zinc nitrate, and aluminum nitrate were mixed at a mass ratio of 2:1:2, and deionized water was added. The solid-liquid ratio was 1:5. The mixture was placed in a sealed container for a constant-temperature, closed-loop hydrothermal reaction. The pH of the system was adjusted to 5.2, and the temperature was raised to 85℃. The mixture was stirred continuously at a constant temperature for 5 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The solid product was separated by vacuum filtration and dried at 105℃ for 2 hours. After pulverization and sieving, intercalation blend precursor particles with a particle size of 2μm to 4μm, a bulk density of 0.32g / cm³ to 0.38g / cm³, and an interlayer spacing of 1.9nm were obtained.

[0052] In-situ interfacial coating treatment: The dried intercalated blend precursor particles were dispersed in anhydrous ethanol system and heated to 65℃. Melamine, urea-formaldehyde monomers and dilute hydrochloric acid catalyst were added, and the pH of the system was adjusted to 5.0. The molar ratio of formaldehyde to amino group was 1.8:1, and the molar ratio of melamine to urea-formaldehyde was 3.2:1. The mixture was stirred continuously to carry out the in-situ interfacial polymerization coating reaction. The reaction was carried out at a constant temperature for 2.5 h. After the reaction was completed, the mixture was cooled, filtered, washed, and dried at low temperature to obtain a fully coated composite precursor (coating thickness 40 nm, melting initiation temperature 116℃).

[0053] Preparation of the first component slurry: Bisphenol F epoxy resin, polycarboxylate ammonium salt dispersant, and polydimethylsiloxane defoamer are added in proportion and mixed until the system is uniform and there are no visible particles. Mixing continues for 30 minutes to obtain a uniform base material. Then, the composite precursor is added to the base material in small amounts in batches. Mix for 5 minutes to break up the agglomerates, and then grind until the slurry fineness is less than 20 μm to obtain the first component slurry.

[0054] Preparation of the second component slurry: Methylhexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent are added in sequence according to the proportion. The mixture is mixed for 15 minutes in a closed, light-proof, and constant temperature environment of 25°C. Air should be avoided during the mixing process. The mixture is then sealed and allowed to stand for 30 minutes to obtain the second component slurry.

[0055] Two-component mixing: The second component is slowly poured into the first component slurry in several batches, and the mixture is kept in a constant temperature and sealed environment at 28°C for 20 minutes. The mixing process is sealed and protected from light to avoid temperature fluctuations. After mixing, the mixture is filtered under pressure using a 120-mesh stainless steel filter to remove impurities and undispersed agglomerates, and the finished coating is obtained (the mass ratio of the first component to the second component is 5:1, and the pot life is 4 hours).

[0056] Substrate pretreatment and spraying: High-pressure dry roughening process is adopted, using 0.8mm quartz sand, controlling the roughening intensity, roughening angle of 75°-80°, and moving the roughening position at a constant speed throughout the process. After treatment, the substrate surface is free of oxide scale, oil stains, and dust, with a surface roughness Ra4.5μm. The coating is completed within 30 minutes after pretreatment, controlling the coating rate and amplitude to ensure uniform wet film thickness. The coating direction is perpendicular to the substrate surface, with a wet film thickness of 150μm, and the coating is completed in a single coat.

[0057] Three-stage gradient temperature curing: The coated substrate is placed in a programmable temperature environment and cured at a temperature increase rate of 1.2℃ / min. The first stage is heated to 65℃ and held at a constant temperature for 25 minutes; the second stage is heated to 116℃ and held at a constant temperature for 50 minutes; the third stage is heated to 155℃ and held at a constant temperature for 35 minutes.

[0058] Post-curing maintenance: Place the cured substrate in a constant temperature and humidity environment (23℃, 50% relative humidity), using a sealed, fully enclosed protection method. Place the substrate horizontally, maintaining a 10-15cm distance from the bottom of the curing environment. Control temperature and humidity fluctuations within ±1℃ and ±2%, respectively. Monitor temperature and humidity in real time throughout the process, recording data every 30 minutes. During the final 48 hours of curing, wipe the coating surface daily with a clean, soft cloth, ensuring no damage to the coating surface, to remove trace amounts of dust. Allow the coating to cure in a sealed environment for 84 hours to obtain the finished anti-corrosion coating.

[0059] Example 2

[0060] A method for preparing an epoxy composite anti-corrosion coating for deep-sea applications is basically the same as that in Example 1, except that the following parameters are adjusted, and the rest of the process is the same as in Example 1:

[0061] 1. The hydrothermal reaction temperature was adjusted to 82℃ and the reaction time was adjusted to 4.5h. The resulting intercalated blend precursor had a particle size of 2.5μm to 4μm and a bulk density of 0.33g / cm³ to 0.37g / cm³.

[0062] 2. The in-situ interface coating reaction temperature was adjusted to 63℃, the reaction time was adjusted to 2.2h, the coating thickness was 38nm, and the melting initiation temperature was 114℃.

[0063] 3. The heating rate of the gradient curing is adjusted to 1.1℃ / min. The first stage is kept at a constant temperature for 28 min, the second stage is kept at a constant temperature for 48 min, and the third stage is kept at a constant temperature for 37 min.

[0064] Example 3

[0065] A method for preparing an epoxy composite anti-corrosion coating for deep-sea applications is basically the same as that in Example 1, except that the following parameters are adjusted, and the rest of the process is the same as in Example 1:

[0066] 1. The mass ratio of sodium-based montmorillonite, zinc nitrate, and aluminum nitrate was adjusted to 2:1.2:2, the solid-liquid ratio was adjusted to 1:4.8, and the pH of the hydrothermal reaction was adjusted to 5.3. The interlayer spacing of the resulting intercalation blend precursor was 1.85 nm.

[0067] 2. The molar ratio of melamine to urea-formaldehyde is adjusted to 3.0:1, the molar ratio of formaldehyde to amino group is adjusted to 1.7:1, the coating thickness is 42nm, and the melting initiation temperature is 118℃.

[0068] 3. Adjust the curing temperature to 22℃, the relative humidity to 48%, and the curing time to 80 hours.

[0069] Comparative Example 1

[0070] The specific steps for using conventional zinc powder as an anti-corrosion filler are as follows:

[0071] Preparation of the first component slurry: Bisphenol F epoxy resin, polycarboxylate ammonium salt dispersant, and polydimethylsiloxane defoamer are added in proportion, mixed evenly, and then zinc powder is added (the amount added is the same as that added to the composite precursor in Example 1). The mixture is then ground until the fineness of the slurry is less than 20 μm to obtain the first component slurry.

[0072] Preparation of the second component slurry: In the same manner as in Example 1, the methyl hexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent were mixed evenly, sealed and allowed to stand to obtain the second component slurry.

[0073] Two-component mixing: Mix the first component and the second component at a mass ratio of 5:1, mix at room temperature for 20 minutes, and then filter to obtain the finished coating.

[0074] Substrate pretreatment and construction: Same as in Example 1, the substrate is treated with a high-pressure dry roughening process and a wet film thickness of 150μm is coated.

[0075] Curing and maintenance: Conventional constant temperature curing (120℃ constant temperature curing for 60 min) was used, and the maintenance conditions were the same as in Example 1. The coating was cured in a sealed environment for 84 h to obtain the finished coating.

[0076] V. Performance Comparison Results of Examples and Comparative Examples

[0077] The finished anti-corrosion coatings prepared in Examples 1, 2, 3, and Comparative Example 1 were subjected to performance tests. The test items included deep-sea peeling rate, substrate adhesion, low-temperature stability (placed at 4°C for 72 hours), pH responsiveness (deep-sea pH=8.2 environment), pressure-triggered self-assembly ability (deep-sea atmospheric pressure 10MPa), and post-curing performance stability. The test results are shown in the table below:

[0078] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Deep-sea stripping rate (mm / d) 0.04 0.045 0.042 0.12 Substrate adhesion (MPa) 18.5 17.8 18.2 10.2 Low temperature stability (4℃, 72h) No embrittlement, no cracking, good flexibility No embrittlement, no cracking, good flexibility No embrittlement, no cracking, good flexibility Slight embrittlement was observed, with fine cracks at the edges. pH responsiveness (pH=8.2) It can quickly activate self-assembly to form a continuous barrier layer. It can activate self-assembly to form a continuous barrier layer. It can quickly activate self-assembly to form a continuous barrier layer. No pH responsiveness, no self-assembly. Pressure-triggered self-assembly capability (10MPa) It can trigger self-assembly, improving the density of the barrier layer. It can trigger self-assembly, and the barrier layer has good density. It can trigger self-assembly, improving the density of the barrier layer. No stress responsiveness, no self-assembly phenomenon Performance stability after maintenance (after 30 days) No performance degradation, no bulging or peeling No significant performance degradation, no bulging or peeling. No performance degradation, no bulging or peeling Performance has slightly decreased, and minor bulging has appeared on the surface.

[0079] As can be seen from the above comparison results, the epoxy composite anti-corrosion coatings for deep-sea use prepared in Examples 1-3 of the present invention are significantly superior to the prior art Comparative Example 1 in terms of deep-sea peeling rate, substrate adhesion, low-temperature stability, pH responsiveness, pressure-triggered self-assembly capability, and performance stability. This fully demonstrates the superiority of the preparation method of the present invention, effectively solves the core technical defects of existing deep-sea epoxy coatings, and can meet the long-term anti-corrosion requirements of deep-sea metal substrates.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An epoxy composite anti-corrosion coating and its preparation method, characterized in that, This includes the following steps performed sequentially: First, a composite precursor was prepared by mixing sodium montmorillonite, zinc nitrate, and aluminum nitrate in a mass ratio of 2:1:2, adding deionized water, and placing the mixture in a sealed container for a constant-temperature, closed-loop hydrothermal reaction. The pH of the system was adjusted to 5.

2. After the reaction was completed, the mixture was filtered and dried at a constant temperature to obtain intercalated blend precursor particles with a bulk density of 0.32 g / cm³ to 0.38 g / cm³ and an interlayer spacing of 1.9 nm. The above-mentioned intercalated blend precursor particles were subjected to in-situ interfacial coating treatment using melamine urea-formaldehyde copolymer. The temperature, pH value and material ratio of the coating reaction were controlled to obtain a composite precursor. To prepare the epoxy resin base material, bisphenol F epoxy resin, polycarboxylic acid ammonium salt dispersant, and polydimethylsiloxane defoamer are added and mixed in sequence until the system is uniform and free of visible particles, thus obtaining the epoxy resin base slurry. The above-mentioned composite precursor is added to the epoxy resin matrix slurry in a specific proportion based on the mass of the epoxy resin matrix. This proportion is determined based on the requirements of coating anti-corrosion performance and viscosity balance. The agglomerates are first mixed and dispersed, and then ground until the slurry fineness is less than 20μm to obtain the first component slurry. The curing agent component was prepared separately. Methylhexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent were added and mixed in sequence. The mixture was then mixed in a closed and light-proof environment until the system was homogeneous to obtain the second component slurry. The first component slurry and the second component slurry were mixed at a mass ratio of 5:1 and continuously mixed in a constant temperature and sealed environment at 28℃. The temperature was controlled to remain stable throughout the process to obtain the finished coating. First, the surface of the deep-sea pipeline metal substrate is roughened, and the roughening intensity and angle are controlled to remove the oxide scale and oil stains on the substrate surface. Then, the finished coating is applied to the pretreated substrate surface, and the coating rate and amplitude are controlled to ensure uniform wet film thickness, thus obtaining a wet film coating. The coated substrate is placed in a programmable heating environment and cured in three stages at a heating rate of 1.2℃ / min. The cured substrate is placed in a constant temperature and humidity environment for static curing to release internal stress and stabilize performance, resulting in a finished anti-corrosion coating.

2. The epoxy composite anti-corrosion coating and its preparation method according to claim 1, characterized in that, The hydrothermal reaction and post-processing steps for preparing the composite precursor are a linked process: the uniformly mixed powder is mixed with deionized water and placed in a sealed container. After sealing, the temperature is raised to 85°C and continuously stirred at a constant temperature. The pH of the system is adjusted to 5.2 and the reaction is carried out at a constant temperature for 5 hours. After the reaction is completed, the temperature is naturally cooled to room temperature. The solid product is separated by vacuum filtration and then placed in a constant temperature drying environment. It is dried at 105°C for 2 hours. After pulverizing and sieving, intercalated blend precursor particles with a particle size controlled between 2μm and 4μm, a bulk density of 0.32g / cm³ to 0.38g / cm³, and an interlayer spacing of 1.9nm are obtained.

3. The epoxy composite anti-corrosion coating and its preparation method according to claim 2, characterized in that, The in-situ interface coating treatment is a closed-loop process: the dried intercalated blend precursor particles are dispersed in anhydrous ethanol system, heated to 65°C and kept at a constant temperature, melamine, urea-formaldehyde monomers and dilute hydrochloric acid catalyst are added according to a preset ratio, the pH of the system is adjusted to 5.0, the molar ratio of formaldehyde to amino is 1.8:1, and the mixture is continuously stirred to carry out the in-situ interface polymerization coating reaction. The reaction is kept at a constant temperature for 2.5 hours. After the reaction is completed, the mixture is cooled, filtered, washed, and dried at low temperature to obtain a fully coated composite precursor. The coating treatment controls the molar ratio of melamine to urea-formaldehyde to be 3.2:1, the coating layer thickness is controlled at 40 nm, and the coating layer melting initiation temperature is 116°C.

4. The epoxy composite anticorrosive coating and its preparation method according to claim 3, characterized in that, The first component slurry is prepared using a dispersion process: bisphenol F epoxy resin, polycarboxylate ammonium salt dispersant, and polydimethylsiloxane defoamer are added in proportion and mixed until the system is uniform and free of visible particles. The mixture is then continuously mixed for 30 minutes to obtain a uniform base material. The composite precursor is then added to the base material in small batches, mixed for 5 minutes to break up the agglomerates, and then ground until the slurry fineness is less than 20 μm to obtain the first component slurry. The amount of composite precursor added is determined based on the requirements of coating anti-corrosion performance and viscosity balance, the amount of dispersant added is determined based on the dispersibility requirements of the first component, and the amount of defoamer added is determined based on the requirements of coating defoaming effect and cost balance.

5. The epoxy composite anti-corrosion coating and its preparation method according to claim 4, characterized in that, The second component slurry is prepared by a mixing process: methyl hexahydrophthalic anhydride modified alicyclic amine curing agent, ethylene glycol monobutyl ether diluent, and polyether modified polydimethylsiloxane leveling agent are added sequentially in proportion, and mixed for 15 minutes in a sealed, light-proof, constant temperature environment of 25°C. Air is avoided during the mixing process to obtain the second component slurry. The amount of diluent added is determined based on the viscosity requirements of the curing agent component, and the amount of leveling agent added is determined based on the coating leveling effect requirements. After the second component is prepared, it is sealed and allowed to stand for 30 minutes before being mixed with the first component.

6. The epoxy composite anti-corrosion coating and its preparation method according to claim 5, characterized in that, The two-component mixing process is a closed-loop process: the second component, after being allowed to stand, is slowly poured into the first component slurry in several batches, and the entire process is carried out in a constant temperature and sealed environment at 28°C for 20 minutes. The mixing process is sealed and protected from light to avoid temperature fluctuations. After mixing, the mixture is filtered under pressure using a 120-mesh stainless steel filter to remove impurities and undispersed agglomerates, resulting in the finished coating. The mass ratio of the first component to the second component is controlled at 5:

1. The pot life of the mixed system is 4 hours.

7. The epoxy composite anticorrosive coating and its preparation method according to claim 6, characterized in that, The substrate pretreatment and spraying process are standardized: the substrate pretreatment adopts a high-pressure dry roughening process, using 0.8mm quartz sand, controlling the roughening intensity, and the roughening angle is controlled between 75° and 80°. The roughening position is moved at a constant speed throughout the process. After treatment, the substrate surface is free of oxide scale, oil, and dust, and the surface roughness is controlled at Ra4.5μm. The coating is completed within 30 minutes after the pretreatment, controlling the coating rate and coating range to ensure uniform wet film thickness. The coating direction is kept perpendicular to the substrate surface, and the coating position is moved at a constant speed. The wet film thickness is controlled at 150μm, and the coating is completed in a single coat.

8. The epoxy composite anti-corrosion coating and its preparation method according to claim 7, characterized in that, The three-stage gradient heating and curing process is a sequentially triggered process, with the heating rate controlled at 1.2℃ / min throughout the process, without drastic temperature fluctuations. The specific segmented process is as follows: the first stage is heated to 65℃ and held at a constant temperature for 25 minutes; the second stage is heated to 116℃ and held at a constant temperature for 50 minutes; and the third stage is heated to 155℃ and held at a constant temperature for 35 minutes.

9. The epoxy composite anti-corrosion coating and its preparation method according to claim 8, characterized in that, The curing process is a closed-loop process: the cured coating substrate is placed in a constant temperature and humidity environment, and cured in a sealed environment for 84 hours at an ambient temperature of 23°C and a relative humidity of 50%. During the curing process, direct sunlight, dust pollution, and external impacts are avoided, and the substrate is not moved throughout the process.

10. The epoxy composite anticorrosive coating and its preparation method according to claim 9, characterized in that, During the curing process, a fully enclosed, sealed protective method is used. The substrate is placed horizontally, maintaining a distance of 10-15cm from the bottom of the curing environment. The temperature fluctuation of the curing environment is controlled within ±1℃, and the relative humidity fluctuation is controlled within ±2%. Temperature and humidity are monitored in real time throughout the process, and the temperature and humidity data are recorded every 30 minutes. If the temperature and humidity exceed the set range, they are immediately adjusted and restored to the set values ​​within 10 minutes. In the later 48 hours of curing, the coating surface is wiped daily with a dust-free soft cloth, taking care not to damage the coating surface, to remove any trace dust adhering to the surface.

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