Self-repairing solvent-free epoxy heavy-duty anticorrosive coating material and preparation and use method thereof

Abstract

The present application relates to a kind of self-repairing solvent-free epoxy heavy-duty coating and its preparation and use method, belong to epoxy resin coating technical field.The coating is composed of A, B component;A component includes epoxy resin matrix, first microcapsule dispersed therein, inhibitor microcapsule and amino functionalized graphene nanosheet, the first microcapsule core is low viscosity epoxy healing agent, and the wall is polyurea, the core of inhibitor microcapsule is volatile inhibitor, and the wall is polylactic acid;B component includes modified amine curing agent and the second microcapsule dispersed therein, and the core of second microcapsule is latent curing agent, and the wall is polymethyl methacrylate.The coating of the present application has self-repairing and heavy-duty function, is suitable for the harsh corrosion environment of ship, aircraft, high-speed rail, ocean engineering and other fields, can significantly prolong the service life of component.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin coating technology, specifically to a self-healing solvent-free epoxy heavy-duty anti-corrosion coating and its preparation and application methods. Background Technology

[0002] Invention patent CN113652140B discloses an epoxy heavy-duty anti-corrosion coating and its application. It prepares Zn-GQDs composite powder by using a carbonized "carbon source + zinc powder." The resulting Zn-GQDs composite powder exhibits excellent compatibility with epoxy resin, allowing for uniform dispersion within the resin. This solves the dispersion and uniformity problems associated with directly adding few-layer graphene and avoids the poor compatibility between zinc-rich powder and epoxy resin, thus facilitating the formation of a uniform heavy-duty anti-corrosion coating. The cured coating demonstrates excellent anti-corrosion performance, with a salt spray resistance exceeding 3000 hours. The coating is low-cost and flexible. The core breakthrough of this technology lies in effectively addressing the common problem of poor agglomeration and dispersion of few-layer graphene in traditional epoxy systems, as well as the inherent challenge of insufficient compatibility between zinc-rich powder and the resin matrix, thereby successfully constructing a novel composite protection system. By introducing Zn-GQDs composite powder, this coating significantly improves the overall corrosion resistance and flexibility of the coating, enhances the coating's ability to resist the penetration of corrosive media to a certain extent, and provides additional electrochemical protection for the metal substrate through the sacrificial anode effect of zinc powder, exhibiting a relatively ideal protective effect in the early stages of coating service.

[0003] Invention patent CN103031040B discloses a solvent-free anti-corrosion coating for oil pipelines, comprising epoxy resin and modified ammonia-based curing agent, characterized by further including corundum, defoamer, deaerator, and modified castor oil-based thixotropic agent. This patent emphasizes the use of a solvent-free formulation, aiming to significantly reduce the emission of volatile organic compounds (VOCs), highly meeting the current urgent need for environmentally friendly coatings. Simultaneously, by strategically adding hard fillers such as corundum to the coating formulation, the coating significantly improves its wear resistance and physical density, further enhancing its effectiveness as a physical barrier and its protective ability against the substrate. The successful application of this technology, particularly in industrial fields such as oil pipelines where both environmental and mechanical protection requirements are high, effectively extends the service life of related equipment, fully demonstrating the effort to achieve a delicate balance between environmental benefits and anti-corrosion performance.

[0004] In practical applications, whether it's a system based on Zn-GQDs composite powder to enhance corrosion resistance or a coating that uses solvent-free formulations combined with hard fillers to improve physical protection, both are essentially "passive protection" mechanisms. Once the coating suffers localized damage under external mechanical impact, friction, erosion, or extreme temperature stress—such as tiny scratches, cracks, peeling, or even microscopic defects invisible to the naked eye—the integrity of its core protective barrier is compromised. In these damaged areas, corrosive media can easily penetrate the coating's physical or electrochemical barriers, directly contacting the protected metal substrate, thus bypassing most of the coating's excellent macroscopic properties and triggering rapid and uncontrollable localized corrosion. This localized corrosion not only accelerates its spread but also ultimately leads to the premature failure of the entire anti-corrosion system.

[0005] Existing epoxy heavy-duty anti-corrosion coatings have made some progress in solvent-free processes and improved initial anti-corrosion performance. However, the problem of a sharp decline in anti-corrosion performance due to local damage under complex working conditions, as well as the coating's sensitivity to the construction environment, resulting in initial defects and a lack of self-repair ability after damage, seriously restrict the long-term reliability of the coating and its application potential in extreme environments. Summary of the Invention

[0006] The purpose of this invention is to provide a self-healing solvent-free epoxy heavy-duty anti-corrosion coating and its preparation and application method, which can effectively solve the technical problems of existing epoxy heavy-duty anti-corrosion coatings lacking an effective self-healing mechanism for local damage and being sensitive to the construction environment when facing complex and variable service environments, thereby significantly improving the long-term anti-corrosion reliability and toughness of the coating.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A self-healing solvent-free epoxy heavy-duty anti-corrosion coating, the coating being a mixture of component A and component B;

[0009] Component A comprises an epoxy resin matrix, a first microcapsule dispersed in the epoxy resin matrix, corrosion inhibitor microcapsules dispersed in the epoxy resin matrix, and functionalized nanofillers dispersed in the epoxy resin matrix. The core of the first microcapsule contains a low-viscosity epoxy healing agent, and the capsule wall is composed of polyurea material. The core of the corrosion inhibitor microcapsule contains a volatile corrosion inhibitor, and the capsule wall is composed of polylactic acid material. The functionalized nanofiller is an amino-functionalized graphene nanosheet.

[0010] Component B contains a modified amine curing agent and a second microcapsule dispersed in the modified amine curing agent. The modified amine curing agent is used to initiate the curing reaction of the epoxy resin matrix. The core of the second microcapsule contains a latent curing agent, and the capsule wall is made of polymethyl methacrylate material.

[0011] Furthermore, the epoxy resin matrix in component A comprises bisphenol A type epoxy resin, bisphenol F type epoxy resin, and a reactive diluent. The epoxy equivalent of the bisphenol A type epoxy resin is limited to 170-190 g / eq, and the viscosity at 25°C is limited to 10000-14000 mPa·s; the epoxy equivalent of the bisphenol F type epoxy resin is limited to 160-180 g / eq, and the viscosity at 25°C is limited to 1500-3000 mPa·s; the mass ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin is from 1:1 to 3:1.

[0012] Furthermore, the reactive diluent is a compound of C12-C14 alkyl glycidyl ether and neopentyl glycol diglycidyl ether in a mass ratio of 1:1 to 3:1, wherein the C12-C14 alkyl glycidyl ether is a monofunctional reactive diluent and the neopentyl glycol diglycidyl ether is a difunctional reactive diluent; the total amount of reactive diluent added accounts for 5% to 15% of the total mass of the epoxy resin matrix, and the amount added is precisely controlled so that the viscosity of component A at 25°C is maintained in the range of 2000-4000 mPa·s.

[0013] Furthermore, the core of the first microcapsule contains a low-viscosity epoxy healing agent, which is a bisphenol F type epoxy resin with an epoxy equivalent of 160-180 g / eq and a viscosity of less than 500 mPa·s at 25°C.

[0014] The capsule wall is made of polyurea material with an average wall thickness of 100-300 nm. The average particle size of the first microcapsule is 50-500 μm, and the narrow particle size distribution is controlled to ensure uniform dispersion and effective release.

[0015] The core of the corrosion inhibitor microcapsule contains a volatile corrosion inhibitor, which is either benzotriazole or 2-mercaptobenzimidazole. The capsule wall is made of polylactic acid (PLA), and the molecular weight and crystallinity of the PLA capsule wall have been optimized so that the PLA capsule wall can release more than 50% of the core corrosion inhibitor within 24 hours in an aqueous environment with a pH of 5-8. The average particle size of the corrosion inhibitor microcapsule is 30-300 μm, which is smaller than that of the first microcapsule.

[0016] Furthermore, the functionalized nanofiller is an amino-functionalized graphene nanosheet with a lateral dimension of 1-5 μm, a thickness of 1-10 nm, and a surface amino functional group density of 0.5-1.5 mmol / g; the addition amount of the functionalized nanofiller in the coating is 0.5-3 wt%.

[0017] Component A also contains at least one additive selected from leveling agents, defoamers, dispersants, antisettling agents, and pigments and fillers.

[0018] Furthermore, the modified amine curing agent in component B is a prepolymer adduct of isophorone diamine and bisphenol A type epoxy resin with an epoxy equivalent of 180-220 g / eq; the amine hydrogen equivalent of the modified amine curing agent is in the range of 80-120 g / eq, and the viscosity at 25°C is less than 1000 mPa·s.

[0019] Furthermore, the core of the second microcapsule contains a latent curing agent, which is 2-methylimidazole; the capsule wall is made of polymethyl methacrylate material with an average wall thickness of 150-350 nm, which is higher than the wall thickness of the first microcapsule; the average particle size of the second microcapsule is 50-500 μm; and the particle size distribution of the first microcapsule and the particle size distribution of the second microcapsule are precisely matched, wherein the ratio of D90 of the first microcapsule to D10 of the second microcapsule is not greater than 1.5;

[0020] Wherein, D90 indicates that 90% of the microcapsule particles are smaller than this value; D10 indicates that 10% of the microcapsule particles are smaller than this value.

[0021] Furthermore, the molar ratio of the epoxy group of the epoxy healing agent in the core material of the first microcapsule to the imidazole catalytic active center of the latent curing agent (2-methylimidazole) in the core material of the second microcapsule is 100:1 to 100:5.

[0022] In addition, this invention also discloses a method for preparing a self-healing solvent-free epoxy heavy-duty anti-corrosion coating, comprising the following steps:

[0023] a) Preparation of component A: First, the epoxy resin matrix, functionalized nanofiller and additives are placed in a mixing and dispersing device with vacuum suction function. Under vacuum conditions of -0.08MPa to -0.095MPa, the above components are dispersed to uniformity by high-speed dispersion.

[0024] Subsequently, under inert gas protection, ensuring the shear force is less than 500s... -1 At a stirring rate of 100°C, the prepared first microcapsules and corrosion inhibitor microcapsules were slowly added to the uniformly dispersed epoxy resin matrix, and the mixture was stirred and dispersed at a low speed for 15-30 minutes.

[0025] Finally, the uniformly mixed component A is degassed under vacuum.

[0026] b) Preparation of component B:

[0027] The modified amine curing agent was placed in a mixing device, and the shear force was less than 300s. -1 Under low-speed stirring conditions, the prepared second microcapsules are slowly added to the modified amine curing agent and stirred for 20 to 40 minutes to ensure uniform dispersion of the second microcapsules in the curing agent and to avoid microcapsule rupture.

[0028] c) Before construction, mix the prepared component A with component B. The mixing process should be carried out using a low-speed electric stirrer at a speed of 100-300 rpm for 3-5 minutes to ensure that the two components are fully mixed.

[0029] In addition, the present invention also discloses a component whose metal surface is coated with the above-mentioned self-healing solvent-free epoxy heavy-duty anti-corrosion coating, and the component is used in harsh corrosive environments such as marine atmospheric environments, chemical atmospheric environments, or environments immersed in seawater / chemical solutions.

[0030] In addition, the present invention also discloses a method for using a self-healing solvent-free epoxy heavy-duty anti-corrosion coating, wherein the self-healing solvent-free epoxy heavy-duty anti-corrosion coating is applied to the metal surface of the component.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention effectively overcomes the inherent defect of traditional anti-corrosion coatings, which suffer a sharp decline in protective ability after damage, and greatly extends the service life of protected components in extreme corrosive environments. When the coating suffers mechanical damage, the first microcapsule releases a low-viscosity epoxy healing agent, and the second microcapsule releases a latent curing agent. The two react and solidify rapidly at the damage site, forming a dense repair. The scratch healing rate can reach 92% within 24 hours, effectively restoring the integrity of the coating. At the same time, the corrosion inhibitor microcapsules intelligently respond to changes in environmental pH, rapidly releasing volatile corrosion inhibitors in acidic corrosive environments to form a passivation film on the metal surface, providing immediate electrochemical protection and inhibiting the initial development of corrosion. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the self-healing process of the self-healing coating of the present invention.

[0035] Figure 2 This is a flowchart of the anti-corrosion construction method of the present invention. Detailed Implementation

[0036] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive. The following description is in conjunction with the accompanying drawings. Figure 1 and Figure 2 The embodiments of the present invention will be described in detail below.

[0037] Example 1:

[0038] See Figure 1 This embodiment discloses a self-healing solvent-free epoxy heavy-duty anti-corrosion coating and its preparation and application methods. Through material design and synergistic effects, the coating aims to significantly improve its long-term anti-corrosion reliability and toughness in complex service environments, effectively overcoming the protective failure problem caused by localized damage in traditional coatings. The realization of this technical solution relies on the precise ratio of component A and component B and the synergistic effect of the multifunctional components, ensuring comprehensive optimization of the coating in terms of macroscopic mechanical properties, microscopic self-healing ability, and corrosion protection mechanism.

[0039] In one specific embodiment, the self-healing solvent-free epoxy heavy-duty anti-corrosion coating is composed of component A and component B mixed in a predetermined mass ratio, and components A and B are stored and transported independently during storage and transportation.

[0040] Component A comprises an epoxy resin matrix, dispersed first microcapsules and corrosion inhibitor microcapsules, functionalized nanofillers, and various other additives. The epoxy resin matrix is ​​composed of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and a reactive diluent. Specifically, the bisphenol A type epoxy resin is a liquid epoxy resin with an epoxy equivalent weight (EEW) precisely controlled within the range of 170-190 g / eq, and a viscosity maintained at 10000-14000 mPa·s at 25°C. Due to its multifunctional characteristics, this bisphenol A type epoxy resin can form a highly cross-linked network structure after curing, thereby endowing the coating with excellent mechanical strength and hardness, forming the core framework of the coating's physical barrier function. Meanwhile, the bisphenol F type epoxy resin is also a liquid epoxy resin, with an epoxy equivalent limited to the range of 160-180 g / eq, and a low viscosity at 25°C, ranging from 1500-3000 mPa·s. The bisphenol F type epoxy resin has a smaller molecular size and lower viscosity, which not only helps to reduce the initial viscosity of the entire epoxy resin matrix and improve the rheological properties of the coating during application, but also, due to the flexibility of its molecular chains, can improve the toughness of the coating to a certain extent and alleviate curing shrinkage stress. In the epoxy resin matrix, the mass ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin ranges from 1:1 to 3:1. This ratio has been precisely selected to achieve an optimal balance between the mechanical strength and flexibility of the coating, ensuring that the coating can resist external mechanical impact without being prone to cracking due to excessive rigidity, while simultaneously reducing the overall viscosity of the system, facilitating the uniform dispersion of subsequent components.

[0041] Furthermore, the reactive diluent is a compound of C12-C14 alkyl glycidyl ether and neopentyl glycol diglycidyl ether, with a mass ratio ranging from 1:1 to 3:1. The C12-C14 alkyl glycidyl ether, as a monofunctional reactive diluent, primarily functions to effectively reduce the overall viscosity of the epoxy resin matrix by introducing long-chain alkyl groups, thereby significantly improving the leveling properties of the coating and reducing brush marks or sagging that may occur during application.

[0042] Meanwhile, the introduction of flexible segments also provides a certain degree of flexibility to the cured coating, which helps to disperse stress. The neopentyl glycol diglycidyl ether, as a bifunctional reactive diluent, not only reduces the viscosity of the system but, more importantly, actively participates in the curing reaction of the epoxy resin, increasing the crosslinking density. This not only helps reduce the internal shrinkage stress of the cured coating but also enhances its resistance to chemical corrosion to a certain extent, making it more resistant to corrosive media such as acids, alkalis, and solvents.

[0043] The total amount of the reactive diluent added accounts for 5% to 15% of the total mass of the epoxy resin matrix. This addition amount was optimized through precise experiments to ensure that the viscosity of component A can be stably maintained within a suitable range of 2000-4000 mPa·s at 25°C. This viscosity range is crucial for the stable suspension of microcapsules in the system, effectively preventing microcapsule sedimentation due to excessively low viscosity or floating due to excessively high viscosity, thus ensuring the uniform distribution of microcapsules in the coating. Furthermore, this viscosity range also ensures excellent leveling properties and good workability of the coating during its application period, facilitating the formation of a high-quality coating.

[0044] Component A also contains dispersed first microcapsules, the core of which contains a low-viscosity epoxy healing agent. This low-viscosity epoxy healing agent is a specific type of bisphenol F epoxy resin with an epoxy equivalent of 160-180 g / eq, and its viscosity at 25°C is strictly controlled to be below 500 mPa·s. The low viscosity of this healing agent is key to its efficient self-healing. When the microcapsules rupture and release due to coating damage, this low-viscosity epoxy healing agent can rapidly and efficiently penetrate and fill the microcracks and scratches. This process is based on the capillary effect, the phenomenon of liquid moving upwards or laterally within tiny channels due to surface tension, ensuring that the healing agent can penetrate every minute corner of the damaged area.

[0045] The first microcapsule's wall is made of polyurea, precisely formed through an interfacial polymerization reaction between isocyanate and amine compounds. Its average wall thickness is controlled within a narrow range of 100-300 nm to provide a preset mechanical strength and rupture threshold, ensuring that the first microcapsule reliably and promptly ruptures and releases its internal healing agent core material when the coating suffers mechanical damage of a predetermined degree (e.g., scratches, impacts). The average particle size of the first microcapsule is 50-500 μm, and particle size distribution is controlled to ensure uniform dispersion of the microcapsules in the epoxy resin matrix. This guarantees that sufficient healing agent is released to the damaged area after coating damage is triggered, thereby achieving self-repair.

[0046] Furthermore, component A contains dispersed corrosion inhibitor microcapsules, the core of which contains a volatile corrosion inhibitor. Specifically, the volatile corrosion inhibitor is benzotriazole or 2-mercaptobenzimidazole. Benzotriazole, as a mature corrosion inhibitor, effectively inhibits the anodic dissolution process of metals and delays the occurrence and development of corrosion by forming a dense and stable physicochemical adsorption film or chelate passivation film with exposed metal surfaces, such as copper and its alloys.

[0047] The 2-mercaptobenzimidazole, through the thiol group contained in its molecule, can form a stronger complexation with the metal surface, providing an additional synergistic corrosion inhibition effect. It exhibits excellent protective capabilities against a variety of metal substrates such as steel, further enhancing the broad-spectrum and efficiency of initial corrosion protection.

[0048] The microcapsules of the corrosion inhibitor are constructed from polylactic acid (PLA) material. The molecular weight and crystallinity of the PLA capsule walls are finely optimized; in an aqueous environment with a pH between 5 and 8, more than 50% of the core corrosion inhibitor can be released within 24 hours. This controlled degradation characteristic ensures that the volatile corrosion inhibitor can be rapidly and targetedly released when the coating suffers mechanical damage and is exposed to corrosive media such as moisture, acid rain, or seawater, environments that are typically accompanied by pH changes.

[0049] The immediate release of the corrosion inhibitor provides immediate and effective electrochemical protection to the exposed metal substrate before the epoxy healing agent and latent curing agent mix and cure to form a new physical barrier. This inhibits the early initiation and spread of corrosion reactions at the microscopic level, buying valuable time for subsequent physical repair. The corrosion inhibitor microcapsules have an average particle size of 30-300 μm, designed to be smaller than the first microcapsule. This size difference ensures that even at minor damage or scratches, the corrosion inhibitor microcapsules can be effectively triggered and release their core material, providing more refined localized protection.

[0050] Component A further comprises functionalized nanofillers, specifically amino-functionalized graphene nanosheets (AMGNs). These AMGNs exhibit significant two-dimensional structural characteristics, with lateral dimensions ranging from 1-5 μm and a thickness of 1-10 nm, and their surface amino functional group density is precisely controlled at 0.5-1.5 mmol / g. The introduction of these amino functional groups is key to distinguishing this invention's nanofillers from traditional nanofillers. These amino functional groups can chemically bond with epoxy groups in the epoxy resin matrix, forming strong covalent bonds. This covalent bonding mechanism is the fundamental guarantee for achieving nanoscale uniform dispersion of the nanofillers in the epoxy matrix, effectively overcoming the agglomeration problem commonly found in traditional unfunctionalized nanofillers in polymer matrices, and ensuring that the performance of the nanofillers is maximized.

[0051] The functionalized nanofiller is added to the coating at an amount of 0.5-3 wt%. Through the chemical bonding and the unique two-dimensional structural characteristics of graphene nanosheets, the functionalized nanofiller significantly improves the overall mechanical and barrier properties of the coating.

[0052] Actual tests showed that the coating's elastic modulus could be increased by more than 20%, and its impact resistance could be increased by more than 30%, indicating that the coating's ability to resist deformation and absorb energy was significantly enhanced.

[0053] More importantly, the nanofiller constructs highly tortuous labyrinthine channels within the coating. When corrosive media attempt to penetrate the coating, they must travel along these winding paths, significantly extending the penetration path and time of the corrosive media within the coating. This greatly enhances the physical barrier properties of the coating, providing more durable protection for the metal substrate.

[0054] Meanwhile, the functionalized nanofiller effectively inhibits the initiation and propagation of microcracks by improving the toughness of the epoxy matrix. This means that when the coating is subjected to mechanical stress, it can resist greater damage without immediately forming macrocracks, thereby extending the damage threshold of the coating and providing a longer response time and higher reliability for the subsequent activation of the self-healing system.

[0055] In a preferred embodiment of the present invention, component A further comprises various other additives to further optimize the overall performance of the coating, for example:

[0056] The leveling agent is usually a modified polysiloxane compound. Its function is to reduce the surface tension of the coating and promote the uniform spreading of the coating on the substrate surface, thereby eliminating brush marks, roller marks or sagging that may occur during construction, and ensuring that the final coating surface is flat, smooth and free of defects.

[0057] The defoamer, such as polyether-modified organosilicon compounds, is used to effectively eliminate bubbles generated during the preparation, mixing and application of coatings due to stirring or air entrapment. If bubbles are not eliminated in time, they may cause pores to form inside the coating, reducing its physical barrier properties.

[0058] The dispersant, such as a low molecular weight polyamide compound, assists in the uniform dispersion of functionalized nanofillers and other solid particles (such as pigments and fillers) in the epoxy resin matrix. It prevents particle agglomeration through steric hindrance or charge repulsion, thus ensuring the stability and performance consistency of the system.

[0059] The anti-settling agent is usually fumed silica, which forms a thixotropic structure in the system to effectively prevent heavy solid particles (such as pigments, fillers, and microcapsules) from settling due to gravity during storage, thus ensuring the uniformity and storage stability of the coating.

[0060] The pigments and fillers are selected according to specific needs. For example, titanium dioxide is mainly used to provide the coating with hiding power, giving it the required color and appearance, while also possessing excellent weather resistance and UV resistance, thus delaying coating aging. Barium sulfate, as an inert filler, can be used to improve the mechanical strength, hardness, and wear resistance of the coating. Mica iron oxide (MIO), due to its unique lamellar structure and chemical stability, forms a "fish scale effect" in the coating, significantly enhancing the coating's shielding and protection capabilities, and further extending the penetration path of corrosive media.

[0061] Component B mainly comprises a modified amine curing agent and a second microcapsule dispersed therein. The modified amine curing agent is a prepolymer addition reaction of isophorone diamine (IPDA) and a low molecular weight epoxy resin. The low molecular weight epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 180-220 g / eq. The prepolymer addition reaction of isophorone diamine with the low molecular weight epoxy resin is a key improvement of this invention. This prepolymerization reaction effectively reduces the volatility and toxicity of isophorone diamine itself, thereby significantly improving the safety of the construction environment.

[0062] Meanwhile, the increased molecular weight and adjusted molecular structure of the prepolymer significantly reduced the viscosity of the curing agent system, improving the mixing and application performance of the coating. Through the prepolymerization reaction, the modified amine curing agent's tolerance to humid environments (i.e., anti-whitening performance) was significantly improved, which is particularly important when applying the coating in humid or high-humidity environments, effectively preventing defects such as surface whitening or incomplete curing caused by moisture interference.

[0063] The modified amine curing agent has an amine hydrogen equivalent weight (AHEW) ranging from 80 to 120 g / eq, and a viscosity of less than 1000 mPa·s at 25°C. The introduction of this curing agent enables the coating of this invention to reliably cure within a wide ambient temperature range of 5-40°C and a relative humidity of 30% to 85%, with a surface drying time controlled within 12 hours and a complete curing time not exceeding 7 days. This broadens the coating's application window, reduces its dependence on strict on-site application conditions, and effectively reduces initial coating defects caused by unsatisfactory curing conditions, thereby improving the stability and reliability of the coating quality.

[0064] The B component also contains dispersed second microcapsules, the core of which contains a latent curing agent for initiating the curing of the low-viscosity epoxy healing agent. The latent curing agent is 2-methylimidazole, which, as a highly efficient epoxy resin curing catalyst, can rapidly initiate the polymerization reaction of the epoxy resin under specific conditions (e.g., after mixing with epoxy resin at room temperature), achieving rapid curing.

[0065] Healing agent curing performance test:

[0066] Curing time: The differential scanning calorimeter (DSC, TAQ2000) was used for testing. The heating rate was 10℃ / min, and the temperature was increased from 25℃ to 200℃. The start time of the exothermic peak (curing start) and the end time of the exothermic peak (curing completion) were recorded. The curing time at room temperature (25℃) was 30-60 minutes.

[0067] Curing degree: Fourier transform infrared spectroscopy (FTIR, Nicoleti S50) was used for testing, and the curing degree was determined by the characteristic peak of the epoxy group (910 cm⁻¹). -1 The degree of curing is calculated as follows: degree of curing = (1 - absorbance after curing / absorbance before curing) × 100%. After curing at room temperature for 24 hours, the degree of curing is ≥90%, which proves that the healing agent has fully cured and formed a dense repair body.

[0068] The capsule wall is made of polymethyl methacrylate (PMMA) material, formed through sophisticated polymerization techniques such as suspension polymerization or emulsion polymerization. The average wall thickness is precisely controlled within the range of 150-350 nm. This wall thickness is designed to be slightly greater than that of the first microcapsule, but its mechanical strength is synergistically designed with the strength of the first microcapsule's wall. This ensures that when the coating suffers localized mechanical damage leading to microcapsule rupture, the first and second microcapsules can rupture synchronously and reliably in a predetermined ratio, releasing their core material. The average particle size of the second microcapsule is 50-500 μm, and its particle size distribution is precisely matched to that of the first microcapsule.

[0069] Furthermore, the ratio of the D90 of the first microcapsule (indicating that 90% of the microcapsules are smaller than this value) to the D10 of the second microcapsule (indicating that 10% of the microcapsules are smaller than this value) is precisely controlled to be no greater than 1.5. This precise particle size distribution matching enables efficient self-healing, ensuring that when the coating suffers localized mechanical damage leading to microcapsule rupture, the first and second microcapsules can release their respective core materials in a predetermined, near-synchronous manner. Through a synergistic release mechanism, the low-viscosity epoxy healing agent and the latent curing agent can be fully and uniformly mixed at the damaged site and undergo a rapid curing reaction, thereby forming a repair body with excellent physical and mechanical properties. This achieves autonomous repair of the damaged area, restoring the physical integrity and barrier properties of the coating, and avoiding the problem of low repair efficiency caused by premature or delayed release of one component.

[0070] In a preferred embodiment of the present invention, the mass ratio of the core material in the first microcapsule to the second microcapsule, calculated based on the molar ratio of the epoxy groups in the epoxy healing agent to the imidazole catalytically active centers in 2-methylimidazole, is 100:1 to 100:5. This molar ratio range ensures that the latent curing agent 2-methylimidazole can provide sufficient catalytic activity during the repair reaction to rapidly and completely initiate the polymerization and curing reaction of the low-viscosity epoxy healing agent. Within this molar ratio range, the healing agent can fully crosslink to form a dense repair, thereby restoring the physical integrity and barrier properties of the coating in the damaged area. Simultaneously, this ratio also avoids the potential negative impact on the repair performance due to excessive curing agent residue, ensuring key performance indicators such as the mechanical strength and chemical resistance of the repair.

[0071] This invention also provides a method for preparing the above-mentioned self-healing solvent-free epoxy heavy-duty anti-corrosion coating, comprising the following series of precisely controlled steps, aimed at ensuring that each component is fully dispersed, the microcapsules are intact, and ultimately a high-performance coating system is formed:

[0072] Preparation of microcapsules:

[0073] Preparation of the first microcapsule: 100g of a low-viscosity epoxy healing agent (epoxy equivalent 170g / eq, viscosity 300mPa·s at 25°C) was emulsified in 500g of an aqueous phase containing 1% polyvinyl alcohol (PVA). Emulsification was performed at 1000rpm for 10 minutes using a high-speed disperser. Then, 10g of toluene diisocyanate (TDI) was added, followed by the slow dropwise addition of 50g of a 5% ethylenediamine aqueous solution. The reaction was carried out at 25°C for 2 hours. After the reaction was complete, the microcapsules were filtered, washed, and dried at 60°C for 2 hours to obtain polyurea wall microcapsules. The core material loading rate of the microcapsules was 80%, i.e., the percentage of the core material mass to the total mass of the microcapsules. The average particle size was 250μm, with a particle size distribution D10 of 120μm and D90 of 180μm.

[0074] The first method for controlling the loading rate of the microcapsule core material is as follows: The loading rate is controlled by adjusting the mass ratio of the low-viscosity epoxy healing agent to the aqueous phase during the emulsification stage. In this example, the ratio is 1:5. For every 0.2 increase in the mass ratio, such as 1:4.8, the loading rate increases by about 5%. The loading rate is determined by the Soxhlet extraction method: 1g of dried microcapsules are taken and extracted with dichloromethane under reflux for 4 hours. The extract is collected and evaporated to dryness. The mass of the core material is weighed, and the loading rate is calculated as 'core material mass / total mass of microcapsules × 100%'. The target loading rate is 80% ± 2%.

[0075] Preparation of corrosion inhibitor microcapsules: 10g of polylactic acid (PLA) with a molecular weight of 50,000 was dissolved in 100g of dichloromethane, and 5g of benzotriazole was added and stirred until dissolved. This solution was emulsified in 500g of an aqueous phase containing 1% polyvinyl alcohol at 500rpm for 30 minutes. The solvent was then evaporated at 40°C for 2 hours, filtered, washed, and dried at 50°C for 2 hours to obtain PLA wall microcapsules. The core material loading rate of the microcapsules was 70%, the average particle size was 150μm, and the particle size distribution was D10 of 100μm and D90 of 200μm.

[0076] Method for controlling the loading rate of corrosion inhibitor microcapsule core material: The loading rate is controlled by adjusting the mass ratio of polylactic acid to the core material (benzotriazole or 2-mercaptobenzimidazole). In this embodiment, the mass ratio of polylactic acid to benzotriazole is 2:1, corresponding to a loading rate of 70%. For every 0.1 decrease in the mass ratio, such as 1.9:1, the loading rate increases by about 3%. For every 0.1 increase in the mass ratio, such as 2.1:1, the loading rate decreases by about 3%. The target loading rate is controlled at 70% ± 2%.

[0077] The loading rate was determined by Soxhlet extraction: 1g of dried corrosion inhibitor microcapsules were placed in a Soxhlet extractor, and dichloromethane was used as the extraction solvent. Dichloromethane can dissolve the benzotriazole / 2-mercapsule-benzimidazole core, but not the polylactic acid capsule wall. The extraction was carried out by reflux for 6 hours. The extract was collected and evaporated to dryness in a rotary evaporator at 60℃ under a vacuum of -0.09MPa. The mass of the residual core solid was weighed. The loading rate was calculated according to the formula 'Core material loading rate = (core solid mass / microcapsule sample mass) × 100%'. The test was performed in parallel for 3 times, and the average value was taken as the final loading rate result.

[0078] Preparation of the second microcapsule: 10g of 2-methylimidazole was dissolved in 50g of methyl methacrylate (MMA) monomer, and 0.5g of benzoyl peroxide (BPO) was added as an initiator. This solution was dispersed in 500g of an aqueous phase containing 1% polyvinyl alcohol (PVA), and suspension polymerization was carried out at 300rpm and reacted at 70°C for 4 hours. After the reaction was completed, the microcapsules were filtered, washed, and dried at 60°C for 2 hours to obtain PMMA wall microcapsules. The core material loading rate of the microcapsules was 85%, the average particle size was 260μm, and the particle size distribution D10 was 120μm and D90 was 200μm.

[0079] The second method for controlling the loading rate of the microcapsule core material is as follows: The loading rate is controlled by adjusting the mass ratio of methyl methacrylate (MMA) to 2-methylimidazole in the core material. In this embodiment, the mass ratio of MMA to 2-methylimidazole is 5:1, corresponding to a loading rate of 85%. For every 0.2 decrease in the mass ratio, such as 4.8:1, the loading rate increases by about 4%. For every 0.2 increase in the mass ratio, such as 5.2:1, the loading rate decreases by about 4%. The target loading rate is controlled at 85% ± 2%.

[0080] The loading rate was determined by Soxhlet extraction: 1 g of dried second microcapsules were placed in a Soxhlet extractor and extracted with acetone as the extraction solvent (acetone can dissolve the 2-methylimidazole core but not the polymethyl methacrylate (PMMA) capsule wall). The extraction was refluxed for 5 h. The extract was collected and evaporated to dryness in a rotary evaporator at 50 °C under a vacuum of -0.09 MPa. The mass of the residual 2-methylimidazole solid was weighed. The loading rate was calculated according to the formula 'core material loading rate = (mass of 2-methylimidazole solid / mass of microcapsule sample) × 100%'. The test was performed in parallel for 3 times, and the average value was taken as the final loading rate result.

[0081] (a) Preparation of component A:

[0082] First, the epoxy resin matrix (including bisphenol A type epoxy resin, bisphenol F type epoxy resin and reactive diluent), functionalized nanofiller (amino-functionalized graphene nanosheets) and other additives (such as leveling agents, defoamers, dispersants, anti-settling agents, pigments and fillers) are precisely measured according to the predetermined formula and then placed together in a mixing and dispersing device with vacuum suction function.

[0083] In practical applications, before adding microcapsules, the surface of the microcapsules is pretreated with silane coupling agent KH-550 to improve their dispersibility and interfacial bonding in epoxy matrix.

[0084] Under vacuum conditions ranging from -0.08 MPa to -0.095 MPa, the above components were continuously dispersed using a high-speed dispersion device (with the linear velocity of the dispersion paddle set to 15-25 m / s) for 60-120 minutes. This high-speed dispersion process aims to ensure that the functionalized nanofillers are uniformly dispersed at the nanoscale in the epoxy matrix. Through the initial chemical bonding reaction between amino functional groups and epoxy groups during dispersion, strong covalent bonds are formed, effectively preventing the aggregation of nanofillers and enhancing their binding force in the matrix.

[0085] Subsequently, ensuring that the shear force is strictly less than 500s -1 At a stirring rate (e.g., the linear velocity of the stirring paddle is controlled at 3-5 m / s), the separately prepared and purified first microcapsules and corrosion inhibitor microcapsules are slowly and uniformly added to the uniformly dispersed epoxy resin matrix under the protection of an inert gas (e.g., high-purity nitrogen, purity ≥99.99%). The inert gas protection effectively prevents unnecessary reactions between the epoxy resin and oxygen or moisture in the air during subsequent operations.

[0086] After adding the capsules, continue to disperse them at low speed for 15 to 30 minutes to ensure that the microcapsules are evenly distributed throughout the system. At the same time, strictly controlling the stirring rate and shear force is the key to avoid the microcapsules from rupturing due to excessive shear force.

[0087] Finally, the uniformly mixed component A is subjected to vacuum degassing. The vacuum level is controlled within the range of -0.08 MPa to -0.095 MPa, and the degassing time is 30 to 60 minutes. This step aims to thoroughly remove any air bubbles that may have been entrained in the system during the mixing and dispersion process, thereby improving the density, strength, and surface quality of the final coating and preventing air bubbles from remaining in the coating and forming pores that would affect its anti-corrosion performance.

[0088] (b) Preparation of component B:

[0089] The synthesized modified amine curing agent was placed in another mixing device. The shear force was strictly less than 300 s. -1 Under low-speed stirring conditions (e.g., stirring paddle linear velocity controlled at 2-4 m / s), the separately prepared and purified second microcapsules are slowly and uniformly added to the modified amine curing agent. Mixing and stirring for 20-40 minutes ensures uniform dispersion of the second microcapsules in the curing agent. Consistent with the principle of adding microcapsules during component A preparation, this process also emphasizes avoiding microcapsule rupture due to excessive shear force, thereby ensuring the integrity of its self-healing function.

[0090] (c) Pre-construction mixing:

[0091] Before actual construction, the prepared component A and component B are precisely measured and mixed according to a predetermined mass ratio, for example, component A: component B = 4:1 to 6:1. The measurement must be strictly performed according to the formula to ensure the stoichiometric balance of the curing reaction.

[0092] The mixing process requires the use of a low-speed electric mixer, with the stirring speed controlled at 100-300 rpm, and the stirring time at 3-5 minutes to ensure that the two components are fully and uniformly mixed. The purpose of the mixing process is to activate the curing reaction, ensuring full contact between the hardener and the epoxy resin, and laying a uniformly dispersed material basis for the subsequent self-healing function. After uniform mixing, the coating is ready for application and should be applied within the specified time.

[0093] See Figure 2 The present invention also provides a method for anti-corrosion construction using the above-mentioned self-healing solvent-free epoxy heavy-duty anti-corrosion coating, characterized by including the following key steps:

[0094] Step 1: Perform surface treatment on the metal substrate.

[0095] First, the metal substrate is sandblasted until it reaches the Sa2.5 cleanliness level specified in ISO 8501-1. This means that the metal surface should be completely free of oxide scale, rust, old paint film, and other contaminants, allowing only a small number of evenly distributed spots or streaks. Simultaneously, by precisely controlling sandblasting parameters, such as selecting appropriate abrasive types (e.g., quartz sand, steel grit, or copper ore sand), abrasive particle size (typically 0.5-1.5 mm), and blasting pressure (typically 0.6-0.8 MPa), a predetermined surface roughness is achieved on the metal substrate, with the surface roughness Ra value controlled within the range of 40-70 μm. This roughness range ensures excellent mechanical adhesion between the coating and the substrate. Through the "anchoring effect" and physical interlocking, the adhesion strength of the coating is significantly improved, providing a reliable physical basis for long-term anti-corrosion performance and effectively preventing coating peeling.

[0096] Step 2: Apply the mixed paint.

[0097] The coating is applied to the treated metal substrate using a high-pressure airless spraying method. High-pressure airless spraying is chosen for its advantages of high efficiency, uniform atomization, and dense coating. The operating pressure range of the high-pressure airless spraying equipment is 15-25 MPa, and the nozzle diameter is typically 0.017-0.023 inches (approximately 0.43-0.58 mm) to ensure that the coating is fully atomized, forming a uniform, pore-free coating. During the spraying process, the spraying distance, speed, and overlap width should be precisely controlled to keep the wet film thickness of a single coat within the range of 150-300 μm. This thickness control ensures sufficient coating thickness to provide initial protection while avoiding sagging, uneven curing, or excessive internal stress due to excessive coating thickness, as well as insufficient protection and premature failure due to insufficient coating thickness. Multiple coats can be applied to achieve the final design thickness, depending on project requirements.

[0098] When applying multiple coats, the interval between coats must meet the following requirements: the previous coat should be surface dry under the construction environment (25℃, 60% relative humidity) before applying the next coat. The standard for judging surface dryness is: using the finger touch method, if the coating surface is not sticky and no coating falls onto the finger, it is considered surface dry. The interval is usually 4-6 hours. If the ambient temperature is below 15℃ or the relative humidity is above 80%, the interval should be extended to 8-12 hours, or the coating surface temperature should be monitored by an infrared thermometer and maintained at 25℃ or above for 1 hour before applying the next coat.

[0099] Step 3: Curing the coating.

[0100] The coating is cured in an ambient temperature range of 5-40℃ and a relative humidity of 30%-85%. These curing conditions fully consider the coating's adaptability to a wide range of environments, enabling stable curing in conventional industrial and outdoor construction environments without the need for additional special heating or dehumidification equipment. After curing, a final protective coating with a total dry film thickness greater than or equal to 300μm is formed. This total thickness ensures the overall corrosion resistance and mechanical strength of the coating, sufficient to resist erosion in harsh corrosive environments.

[0101] The self-healing function of the coating was evaluated through a series of quantitative experiments after it suffered a penetrating scratch. For example, a penetrating scratch with a width of 100-500 μm was prepared on the coating surface using an electric scratch tester, ensuring that the scratch reached the metal substrate. Subsequently, the damaged coating was placed in a 5% NaCl solution, and the repair effect was evaluated after 24 hours.

[0102] This invention also provides a component whose metal surface is coated with a coating formed by the aforementioned self-healing solvent-free epoxy heavy-duty anti-corrosion coating. The component can be widely used in harsh corrosive environments such as marine atmospheric environments, chemical atmospheric environments, or long-term immersion in seawater / chemical solutions, for example, offshore platforms, ship structures, chemical storage tanks, pipelines, and bridges. The coating exhibits significant long-term reliability. When the coating suffers damage less than or equal to 500 μm in width during use, such as mechanical scratches, impact-induced microcracks, fatigue cracks, or localized peeling due to corrosion, its inherent self-healing function can be actively and immediately activated after the damage occurs.

[0103] Specifically, when the coating is damaged, the corrosion inhibitor microcapsules are the first to rupture. The rapidly released volatile corrosion inhibitors (benzotriazole or 2-mercaptobenzimidazole) immediately form a passivation film or complex film on the exposed metal substrate surface, providing immediate and active electrochemical corrosion protection. This effectively inhibits the early occurrence and spread of corrosion reactions, buying time for subsequent physical repair. Almost simultaneously, the first and second microcapsules also rupture due to stress concentration at the damage site, releasing a low-viscosity epoxy healing agent and a latent curing agent (2-methylimidazole), respectively.

[0104] The passivation film / complex film formed by the corrosion inhibitor was characterized by the following methods:

[0105] Film thickness: The film thickness was measured using an ellipsomerometer (JAWoollamM-2000) with a scanning wavelength range of 300-1000nm. The film thickness was calculated using the Cauchy model and was found to be 5-15nm.

[0106] Membrane composition: X-ray photoelectron spectroscopy (XPS, ThermoScientificK-Alpha) was used to analyze the surface elemental composition (such as N, O, and metal elements). The results showed that benzotriazole formed MN bonds with the metal surface (M is the metal substrate element), proving the formation of a complex film.

[0107] Membrane protection performance: Through potentiodynamic polarization curve testing (CHI660E electrochemical workstation), the test solution was 5% NaCl solution, the scan rate was 1mV / s, and the corrosion current density of the sample with film was found to be more than two orders of magnitude lower than that of the sample without film, proving the electrochemical protection effect of the membrane.

[0108] The two core materials are thoroughly mixed in the damaged area, and 2-methylimidazole rapidly catalyzes the curing reaction of the epoxy healing agent, forming a dense and tough repair at the damaged site, thereby restoring the physical integrity and barrier properties of the coating. Through the synergistic effect of the immediate protection of the corrosion inhibitor and the physical repair of the healing agent, the salt spray resistance of the damaged area (tested according to ASTM B117 standard) can be maintained at the same level as the undamaged coating for more than 1000 hours.

[0109] Salt spray resistance: According to ASTM B117-2021 standard, the test conditions were: salt spray chamber temperature 35℃±2℃, salt water 5% NaCl solution, pH 6.5-7.2, adjusted by hydrochloric acid or sodium hydroxide, salt spray deposition rate 1-2 mL / (h·100cm²), continuous spraying; corrosion rating according to ASTM D610-21 standard, using Ri grade (percentage of rust area): Ri10 is no rust, Ri9 is rust area <0.1%, ..., Ri5 is rust area 2%-5%; during the test, the sample was taken out every 200 hours, the surface salt spray residue was rinsed with deionized water, dried and the rust condition of the scratched area was observed, the Ri grade and the corrosion area under the film were recorded, and the percentage of corrosion area was calculated by analyzing the photos using ImageJ software.

[0110] This invention's coating effectively overcomes the inherent defect of traditional anti-corrosion coatings, which suffer a sharp decline in protective capability after damage. It significantly extends the service life of protected components in extreme corrosive environments, reducing maintenance costs and downtime. The self-healing coating of this invention provides long-term, stable anti-corrosion protection even after mechanical damage, significantly improving the safety and economic benefits of industrial components throughout their entire lifecycle.

[0111] To more comprehensively illustrate the technical solution of the present invention and its resulting technical effects, a detailed description will be provided below in conjunction with specific embodiments and comparative examples. These embodiments and comparative examples are not intended to limit the scope of the present invention, but rather to provide more specific and operable implementation paths and performance data for the technical solution of the present invention.

[0112] Preparation and performance evaluation of self-healing solvent-free epoxy heavy-duty anti-corrosion coatings:

[0113] Preparation of component A:

[0114] First, accurately weigh 60 parts of bisphenol A type epoxy resin (EEW ​​185 g / eq, viscosity 12000 mPa·s at 25℃) and 20 parts of bisphenol F type epoxy resin (EEW ​​170 g / eq, viscosity 2000 mPa·s at 25℃). Mix 5 parts of C12-C14 alkyl glycidyl ether with 5 parts of neopentyl glycol diglycidyl ether as a reactive diluent.

[0115] The epoxy resin and reactive diluent were placed in a high-speed disperser equipped with a vacuum suction function. 1.5 parts of amino-functionalized graphene nanosheets (AMGNs, lateral dimension 2 μm, thickness 5 nm, surface amino functional group density 1.0 mmol / g) were added, along with 0.5 parts of modified polysiloxane leveling agent, 0.3 parts of polyether-modified silicone defoamer, 0.2 parts of low molecular weight polyamide dispersant, 1.0 part of fumed silica anti-settling agent, 10 parts of titanium dioxide, and 3 parts of mica iron oxide. The mixture was dispersed at a vacuum of -0.09 MPa and a paddle linear velocity of 20 m / s for 90 minutes to ensure uniform dispersion of the AMGNs and full reaction with the epoxy groups.

[0116] Subsequently, under nitrogen protection, eight portions of the first microcapsules (250 μm average particle size, 200 nm wall thickness polyurea capsules, core of EEW 170 g / eq, viscosity 300 mPa·s at 25℃) and three portions of corrosion inhibitor microcapsules (150 μm average particle size, 180 nm wall thickness polylactic acid capsules, core of benzotriazole) were slowly added under low-speed stirring conditions of 4 m / s, and stirring was continued for 20 minutes. Finally, component A was vacuum degassed for 45 minutes under a vacuum of -0.09 MPa. The viscosity of the obtained component A at 25℃ was 3200 mPa·s.

[0117] In specific implementation, amino-functionalized graphene nanosheets are prepared by the Hummer method to produce graphene oxide, which is then reacted with ammonia and hydrazine hydrate at 80°C for 6 hours. After washing and drying, amino-functionalized graphene nanosheets are obtained, and the surface amino density is determined by acid-base titration.

[0118] In practice,

[0119] Amino-functionalized graphene nanosheets are prepared through the following steps:

[0120] Preparation of graphene oxide (Hummer method): 5g of natural graphite powder was placed in a 500mL polytetrafluoroethylene beaker, and 120mL of concentrated sulfuric acid (98% by mass) was added. The mixture was stirred in an ice bath at 0-5℃ for 30min. 15g of potassium permanganate (KMnO4) was slowly added, and the temperature was controlled to not exceed 20℃. The mixture was stirred for 2h. The temperature was raised to 35℃ and stirred for 30min. 250mL of deionized water was slowly added dropwise, and the temperature was raised to 98℃. The mixture was stirred for 15min. 500mL of deionized water was added to terminate the reaction. 30% hydrogen peroxide (H2O2) was added dropwise until the solution turned bright yellow. The mixture was allowed to stand for 24h. The mixture was centrifuged at 8000rpm for 15min. The solution was washed three times with 5% hydrochloric acid solution, and then washed with deionized water until pH=7. The mixture was then freeze-dried at -50℃ under a vacuum of 10Pa to obtain graphene oxide.

[0121] Amino modification: 2g of graphene oxide was dispersed in 200mL of deionized water and ultrasonically dispersed for 30min at 300W and 20kHz. 10mL of 25% ammonia and 5mL of 80% hydrazine hydrate were added and refluxed at 80℃ for 6h. After the reaction, the mixture was centrifuged at 8000rpm for 15min, washed with deionized water until pH=7, and freeze-dried to obtain amino-functionalized graphene nanosheets. The surface amino density was determined by titration with 0.1mol / L hydrochloric acid standard solution.

[0122] Preparation of component B:

[0123] Accurately weigh 25 parts of modified amine curing agent (IPDA and EEW 200g / eq bisphenol A type epoxy resin prepolymer, AHEW 100g / eq, viscosity 800mPa·s at 25℃). Slowly add 2.5 parts of a second microcapsule with an average particle size of 260μm, a wall thickness of 250nm (PMMA), and a core of 2-methylimidazole, under low-speed stirring at a paddle speed of 3m / s, and stir for 30 minutes to ensure uniform dispersion.

[0124] Coating application and curing:

[0125] After accurately measuring the prepared components A and B at a mass ratio of 4:1, use a low-speed electric stirrer to stir evenly for 4 minutes at a speed of 200 rpm.

[0126] Q235 steel plates were sandblasted to Sa2.5 grade, with a surface roughness Ra value of 55 μm. The mixed coating was then applied to the treated steel plate using a high-pressure airless spraying method at a working pressure of 20 MPa and a nozzle diameter of 0.019 inches. The wet film thickness of each coat was controlled at 200 μm. Two coats were applied to achieve a total dry film thickness of approximately 400 μm. The coating was cured for 7 days at 25°C and 60% relative humidity.

[0127] Performance evaluation:

[0128] Mechanical properties: The elastic modulus of the coating was tested according to ASTM D638 standard, and the result was 2.5 GPa. The impact resistance of the coating was tested according to ASTM D2794 standard, and the result was 1.5 J.

[0129] Elastic modulus test: According to ASTM D638-2014 standard, a Type V specimen with a length of 50 mm, a width of 6 mm, and a thickness of 4 mm was used. Specimen preparation method: The mixed coating was poured into a Type V polytetrafluoroethylene mold, and a release agent was applied to the inner wall. The mold was cured for 7 days at 25℃ and 60% relative humidity. After demolding, the edges of the specimen were sanded with 800-grit sandpaper until smooth. Then, a universal testing machine was used for testing, with a range of 0-5 kN and a loading rate of 2 mm / min. The average value of 5 parallel specimens was taken as the elastic modulus result.

[0130] Scratch self-healing rate: On the cured coating surface, a penetrating scratch approximately 300 μm wide was created using a motorized scratcher until the metal substrate was exposed. The scratched sample was then immersed in a 5% NaCl solution and left at room temperature for 24 hours. The recovery of the scratch area was observed and quantified using scanning electron microscopy (SEM), and the scratch area healing rate was measured to be 92%. The impedance of the healed area was tested by electrochemical impedance spectroscopy (EIS), and the impedance modulus after repair recovered to 95% of the pre-damage value.

[0131] Salt spray resistance: Accelerated salt spray test conducted according to ASTM B117 standard.

[0132] The scratched coating samples were placed in a salt spray chamber for continuous exposure. The corrosion spread and underfilm corrosion in the scratched areas were observed periodically. The results showed that after 1000 hours of salt spray exposure, the rust grade in the scratched areas remained at Ri10 (no obvious rust), and the underfilm corrosion area was less than 5%, which was highly consistent with the performance of the non-destructive coating.

[0133] Comparative Example 1:

[0134] This comparative example aims to prepare a traditional solvent-free epoxy heavy-duty anti-corrosion coating that does not have self-healing function and does not contain functionalized nanofillers, and compare its performance with that of Example 1.

[0135] Preparation of component A:

[0136] Accurately weigh 80 parts of bisphenol A type epoxy resin (EEW ​​185 g / eq, viscosity 12000 mPa·s at 25℃). Mix 5 parts of C12-C14 alkyl glycidyl ether with 5 parts of neopentyl glycol diglycidyl ether as a reactive diluent. Place the epoxy resin and reactive diluent in a high-speed disperser. Add 0.5 parts of modified polysiloxane leveling agent, 0.3 parts of polyether modified silicone defoamer, 0.2 parts of low molecular weight polyamide dispersant, 1.0 part of fumed silica anti-settling agent, 10 parts of titanium dioxide, and 3 parts of mica iron oxide. Disperse at atmospheric pressure with a paddle velocity of 15 m / s for 60 minutes. Degas component A. The viscosity of the obtained component A at 25℃ is 3800 mPa·s.

[0137] Preparation of component B:

[0138] Accurately weigh 30 parts of modified amine curing agent (IPDA and EEW 200g / eq bisphenol A type epoxy resin prepolymer, AHEW 100g / eq, viscosity 800mPa·s at 25℃).

[0139] Coating application and curing:

[0140] After accurately measuring the prepared components A and B at a mass ratio of 4:1, stir them evenly for 4 minutes using a low-speed electric stirrer (200 rpm).

[0141] Q235 steel plates were sandblasted to Sa2.5 grade, with a surface roughness Ra value of 55 μm. The mixed coating was then applied to the treated steel plates using high-pressure airless spraying (working pressure 20 MPa, nozzle diameter 0.019 inches), with a single wet film thickness controlled at 200 μm. Two coats were applied to achieve a total dry film thickness of approximately 400 μm. The coating was cured for 7 days at 25°C and 60% relative humidity.

[0142] Performance evaluation:

[0143] Mechanical properties: The elastic modulus of the coating was tested according to ASTM D638 standard, and the result was 2.0 GPa. The impact resistance of the coating was tested according to ASTM D2794 standard, and the result was 1.0 J.

[0144] Scratch-affected area performance: On the cured coating surface, a penetrating scratch approximately 300 μm wide was created using an electric scratch tester until the metal substrate was exposed. The scratched sample was then immersed in a 5% NaCl solution and left at room temperature for 24 hours. Due to the lack of self-healing capabilities, the scratched area showed no healing. Electrochemical impedance spectroscopy (EIS) testing revealed a significant decrease in the impedance modulus of the scratched area compared to the undamaged area, indicating that it could provide almost no effective physical barrier protection.

[0145] Salt spray resistance: Accelerated salt spray testing was conducted according to ASTM B117. The scratched coating samples were placed in a salt spray chamber for continuous exposure. Results showed that after 1000 hours of salt spray exposure, significant corrosion occurred in the scratched areas, with the corrosion grade dropping below Ri5, accompanied by significant underfilm corrosion propagation and a peeling area exceeding 30%.

[0146] By comparing the performance data of Example 1 and Comparative Example 1, the significant performance improvement brought about by the self-healing solvent-free epoxy heavy-duty anti-corrosion coating of the present invention can be clearly observed. Specific performance comparison results are shown in Table 1:

[0147] Table 1:

[0148]

[0149] The scratch healing rate was calculated by measuring the scratch volume recovery rate using a laser confocal microscope (CLSM) according to standard ISO19208:2016.

[0150] The above data clearly demonstrates the significant technical advantages of the self-healing solvent-free epoxy heavy-duty anti-corrosion coating of this invention over traditional coatings in terms of mechanical properties, scratch self-healing ability, and long-term anti-corrosion performance. In particular, its ability to maintain highly efficient anti-corrosion protection after damage is unmatched by traditional coatings, effectively solving the core pain point of the prior art where the protective ability of the coating drops sharply after local damage.

[0151] Example 2: Effect of different nanofiller contents on coating performance.

[0152] This example aims to investigate the effect of the amount of amino-functionalized graphene nanosheets (AMGNs) added to component A on the mechanical properties and permeation barrier properties of the coating. Except for the AMGNs content, all other components and the preparation, application, and curing conditions were consistent with those in Example 1. Specific test results are shown in Table 2.

[0153] Table 2:

[0154]

[0155] The data above shows that with increasing AMGNs content, the coating's elastic modulus and impact resistance initially increase and then stabilize or slightly decrease, while oxygen permeability continues to decline. When the AMGNs content is 1.5 wt%, the coating exhibits excellent overall performance, with both elastic modulus and impact resistance reaching high levels. When the AMGNs content further increases to 4.0 wt%, although oxygen permeability decreases slightly, impact resistance actually decreases. This may be related to the potential local agglomeration or induced stress concentration of the nanofillers at high contents, leading to impaired coating toughness. Therefore, controlling the nanofiller content within the range of 0.5-3 wt% is crucial for optimizing the overall coating performance.

[0156] Example 3: The effect of microcapsule particle size distribution on self-repair efficiency.

[0157] This embodiment aims to verify the synergistic effect of the particle size distribution matching of the first and second microcapsules on the self-healing efficiency. Except for the microcapsule particle size distribution parameters, all other components and preparation, application, and curing conditions were consistent with those in Example 1. Specific test results are shown in Table 3.

[0158] Table 3:

[0159]

[0160] The data above show that when the ratio of D90 of the first microcapsule to D10 of the second microcapsule is no greater than 1.5, the scratch healing rate and impedance recovery rate of the healed area of ​​the coating can both be maintained at a high level, achieving efficient self-healing. The performance is optimal, especially at a ratio of 1.0. However, when the ratio increases to 2.0, i.e., D90 (first) is significantly greater than D10 (second), the healing efficiency decreases significantly. This indicates that precise matching of microcapsule particle size distribution is crucial to ensuring synchronous and sufficient release and mixing of the two core materials at the damage site. Excessive particle size difference may lead to asynchronous release or uneven mixing of the healing agent and curing agent, thereby reducing repair efficiency.

[0161] In summary, this invention successfully solves the problem of drastic decline in protective capability after coating damage in existing technologies through ingenious component design and synergistic mechanisms. From the mechanical balance of the epoxy resin matrix, the viscosity control and performance contribution of the reactive diluent, the precise rupture and release of the healing agent microcapsules, the intelligent responsive degradation of the corrosion inhibitor microcapsules, the strengthening, toughening, and barrier effects of functionalized nanofillers, to the broad environmental adaptability of the curing agent system and the synergistic release mechanism of the latent curing agent microcapsules, every aspect has been meticulously optimized. This constructs a highly efficient and reliable self-healing anti-corrosion system, providing unprecedented long-term stable protection for industrial components in harsh corrosive environments. The meticulous preparation method and scientific application method ensure the operability and performance stability of the coating in practical applications. Through specific examples and quantified performance data, the superiority of this invention has been fully demonstrated, bringing a revolutionary solution to the field of heavy-duty corrosion protection.

[0162] Example 4:

[0163] In Example 1, the corrosion inhibitor microcapsules degraded too quickly in an acidic environment, leading to premature release of the corrosion inhibitor. This example provides a pH-responsive corrosion inhibitor microcapsule that triggers release only in acidic corrosive environments.

[0164] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the capsule wall of the corrosion inhibitor microcapsule is composed of dimethylaminoethyl methacrylate-methacrylic acid copolymer (DMAEMA-co-MAA), wherein the molar ratio of DMAEMA to MAA is 7:3. This copolymer swells at pH ≤ 5, releasing the core corrosion inhibitor; it remains stable at pH ≥ 7.

[0165] Specifically as follows:

[0166] Synthesis of DMAEMA-co-MAA copolymer: DMAEMA (7 mol), MAA (3 mol) and AIBN (0.5 wt%) were dissolved in toluene and reacted under nitrogen protection at 70 °C for 6 h. The precipitate was placed in petroleum ether and dried to obtain the copolymer (Mn≈30,000).

[0167] Preparation of corrosion inhibitor microcapsules: 5 g of benzotriazole and 10 g of DMAEMA-co-MAA copolymer were dissolved in 100 g of dichloromethane, emulsified in 500 g of 1% PVA aqueous solution (800 rpm, 30 min), the solvent was evaporated at 40℃ for 3 h, filtered and dried to obtain microcapsules with an average particle size of 180 μm and a wall thickness of 200 nm.

[0168] The specific test data is shown in Table 4:

[0169] Table 4:

[0170]

[0171] This embodiment achieves precise release in acidic environments through pH-responsive microcapsules, avoiding ineffective losses in neutral or alkaline environments, and improving repair efficiency and environmental adaptability.

[0172] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0173] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing solvent-free epoxy heavy-duty anti-corrosion coating, characterized in that: The coating is composed of a mixture of component A and component B, wherein the mass ratio of component A to component B is 4:1 to 6:

1. Component A comprises an epoxy resin matrix, a first microcapsule dispersed in the epoxy resin matrix, corrosion inhibitor microcapsules dispersed in the epoxy resin matrix, and functionalized nanofillers dispersed in the epoxy resin matrix. The core of the first microcapsule contains a low-viscosity epoxy healing agent, and the capsule wall is composed of polyurea material. The core of the corrosion inhibitor microcapsule contains a volatile corrosion inhibitor, and the capsule wall is composed of polylactic acid material. The functionalized nanofiller is an amino-functionalized graphene nanosheet. Component B contains a modified amine curing agent and a second microcapsule dispersed in the modified amine curing agent. The modified amine curing agent is used to initiate the curing reaction of the epoxy resin matrix. The core of the second microcapsule contains a latent curing agent, and the capsule wall is made of polymethyl methacrylate material.

2. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 1, characterized in that: The epoxy resin matrix in component A includes bisphenol A type epoxy resin, bisphenol F type epoxy resin, and a reactive diluent. The epoxy equivalent of the bisphenol A type epoxy resin is limited to 170-190 g / eq, and the viscosity range at 25°C is 10000-14000 mPa·s. The epoxy equivalent of the bisphenol F type epoxy resin is limited to 160-180 g / eq, and the viscosity range at 25°C is 1500-3000 mPa·s. The mass ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin ranges from 1:1 to 3:

1.

3. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 2, characterized in that: The reactive diluent is a compound of C12-C14 alkyl glycidyl ether and neopentyl glycol diglycidyl ether in a mass ratio of 1:1 to 3:

1. C12-C14 alkyl glycidyl ether is a monofunctional reactive diluent, and neopentyl glycol diglycidyl ether is a difunctional reactive diluent. The total amount of reactive diluent added accounts for 5% to 15% of the total mass of the epoxy resin matrix. The amount added is precisely controlled so that the viscosity of component A is maintained in the range of 2000-4000 mPa·s at 25°C.

4. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 1, characterized in that: The core of the first microcapsule contains a low-viscosity epoxy healing agent, which is a bisphenol F type epoxy resin with an epoxy equivalent of 160-180 g / eq and a viscosity of less than 500 mPa·s at 25℃. The capsule wall is made of polyurea material with an average wall thickness of 100-300 nm. The average particle size of the first microcapsule is 50-500 μm, and the narrow particle size distribution is controlled to ensure uniform dispersion and effective release. The core of the corrosion inhibitor microcapsule contains a volatile corrosion inhibitor, which is either benzotriazole or 2-mercaptobenzimidazole. The capsule wall is made of polylactic acid (PLA), and the molecular weight and crystallinity of the PLA capsule wall have been optimized so that the PLA capsule wall can release more than 50% of the core corrosion inhibitor within 24 hours in an aqueous environment with a pH of 5-8. The average particle size of the corrosion inhibitor microcapsule is 30-300 μm, which is smaller than that of the first microcapsule.

5. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 1, characterized in that: The functionalized nanofiller is an amino-functionalized graphene nanosheet with a lateral dimension of 1-5 μm, a thickness of 1-10 nm, and a surface amino functional group density of 0.5-1.5 mmol / g; the addition amount of the functionalized nanofiller in the coating is 0.5-3 wt%. Component A also contains at least one additive selected from leveling agents, defoamers, dispersants, antisettling agents, and pigments and fillers.

6. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 1, characterized in that: The modified amine curing agent in component B is a prepolymer adduct of isophorone diamine and bisphenol A type epoxy resin with an epoxy equivalent of 180-220 g / eq; the amine hydrogen equivalent of the modified amine curing agent is in the range of 80-120 g / eq, and the viscosity at 25°C is less than 1000 mPa·s.

7. The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to claim 1, characterized in that: The core of the second microcapsule contains a latent curing agent, which is 2-methylimidazole; the capsule wall is made of polymethyl methacrylate material with an average wall thickness of 150-350 nm, which is thicker than that of the first microcapsule; the average particle size of the second microcapsule is 50-500 μm; and the particle size distribution of the first microcapsule and the particle size distribution of the second microcapsule are precisely matched, wherein the ratio of D90 of the first microcapsule to D10 of the second microcapsule is not greater than 1.5; Wherein, D90 indicates that 90% of the microcapsule particles are smaller than this value; D10 indicates that 10% of the microcapsule particles are smaller than this value.

8. A method for preparing the self-healing solvent-free epoxy heavy-duty anti-corrosion coating of claim 5, characterized in that, Includes the following steps: a) Preparation of component A: First, the epoxy resin matrix, functionalized nanofiller and additives are placed in a mixing and dispersing device with vacuum suction function. Under vacuum conditions of -0.08MPa to -0.095MPa, the components are dispersed to uniformity by high-speed dispersion. Subsequently, under inert gas protection, ensuring the shear force is less than 500s... -1 At a stirring rate of 100°C, the prepared first microcapsules and corrosion inhibitor microcapsules were slowly added to the uniformly dispersed epoxy resin matrix, and the mixture was stirred and dispersed at a low speed for 15-30 minutes. Finally, the uniformly mixed component A is degassed under vacuum. b) Preparation of component B: The modified amine curing agent was placed in a mixing device, and the prepared second microcapsules were slowly added to the modified amine curing agent under low-speed stirring conditions with a shear force of less than 300 s⁻¹. The mixture was stirred for 20 to 40 minutes to ensure that the second microcapsules were uniformly dispersed in the curing agent and to avoid the rupture of the microcapsules. c) Before construction, mix the prepared component A with component B. The mixing process should be carried out using a low-speed electric stirrer at a speed of 100-300 rpm for 3-5 minutes to ensure that the two components are fully mixed.

9. A method for applying a self-healing solvent-free epoxy heavy-duty anti-corrosion coating, characterized in that: The self-healing solvent-free epoxy heavy-duty anti-corrosion coating according to any one of claims 1-7 is applied to the metal surface of the component, and the component is used in harsh corrosive environments such as marine atmospheric environments, chemical atmospheric environments, or immersed in seawater / chemical solutions.

Images