A method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of magnetic particles mediated by silane coupling.

Abstract

This invention belongs to the field of anti-corrosion coating preparation technology, and discloses a method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of magnetic particles mediated by silane coupling. First, glass flakes are subjected to alkaline etching to introduce uniform micro-nano pits on the flake surface. Then, iron oxide particles are grown in situ on the etched glass flake surface to obtain a magnetic filler with both high magnetic responsiveness and structural stability. The magnetic filler is then uniformly mixed with water-based epoxy resin and a curing agent and coated onto the surface of a metal substrate. After coating, the substrate is immediately placed in a horizontal, constant magnetic field generated by a solenoid, causing the magnetic filler to be uniformly and horizontally oriented within the coating. After complete curing, the final anti-corrosion coating is obtained. This invention effectively improves the load-bearing strength of magnetic particles and the orientation uniformity of the filler, reduces the porosity of the coating interface, strengthens the horizontal labyrinth barrier effect of the filler, and significantly improves the long-term anti-corrosion performance of the coating, making it suitable for the anti-corrosion application requirements of various industrial metal components.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating preparation technology, and in particular to a method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of magnetic particles mediated by silane coupling. Background Technology

[0002] With the continuous expansion of coastal infrastructure construction, the harsh corrosive environment of high salt spray, high humidity, and strong ultraviolet radiation is constantly increasing the requirements for the service life of coatings. Optimizing the barrier performance of heavy-duty anti-corrosion coatings has become a core research and development direction in the industry.

[0003] Currently, most mainstream flake-reinforced heavy-duty anti-corrosion coatings employ a process of directly coating and curing a mixture of flake fillers such as glass flakes and basalt flakes with a resin matrix. This relies on the physical barrier effect of the flake fillers to extend the diffusion path of corrosive media. This technology is mature, has low raw material costs, and has been widely applied in conventional anti-corrosion scenarios. However, in this type of technology, the flake fillers are randomly and disordered within the coating, and the labyrinth barrier effect is not fully utilized. Furthermore, there is a lack of effective interfacial bonding structure between the flake fillers and the resin matrix, which easily creates interfacial gaps and pores. Corrosive media such as chloride ions and water vapor can easily penetrate along the interface, making it difficult to meet the long-term anti-corrosion requirements of more than 15 years in marine environments.

[0004] Existing publicly available magnetic field-oriented anti-corrosion coating technologies improve the barrier performance of coatings to some extent by loading magnetic components onto the surface of sheet-like fillers and then applying an external magnetic field to drive the fillers to oriented. However, these technologies generally use physical mixing or adsorption to load magnetic particles, resulting in low bonding strength between the magnetic particles and the sheet-like fillers. These particles are prone to detachment during coating and mixing, leading to some fillers losing their magnetic response capability and poor directional uniformity. Furthermore, these technologies do not optimize for key indicators such as magnetic particle size, solenoid operating parameters, and post-coating transfer aging, which can easily lead to problems such as insufficient magnetic response, premature curing of the resin system, and excessive filler deflection resistance. Ultimately, the filler orientation rate is less than 60%, resulting in limited improvement in the coating's anti-corrosion performance.

[0005] In summary, existing anti-corrosion coating preparation technologies suffer from drawbacks such as weak interfacial adhesion, poor filler orientation uniformity, and insufficient magnetic load stability, making them unsuitable for long-term protection requirements in harsh corrosive environments. The industry urgently needs targeted optimization technologies to fill this gap. Summary of the Invention

[0006] To address the shortcomings of existing flake anticorrosion coatings, such as weak interfacial adhesion, poor magnetic filler load stability, low orientation uniformity, and insufficient barrier properties, this invention provides a method for preparing a magnetic field-oriented anticorrosion coating by in-situ growth of magnetic particles mediated by silane coupling.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a magnetic field-oriented anti-corrosion coating with in-situ growth of magnetic particles mediated by silane coupling includes the following steps:

[0009] S1. The sheet-like filler is etched with concentrated alkaline solution at 60~80℃ for 30~60 min. After cleaning until neutral, the etched sheet-like filler is modified with a silanol aqueous solution with pH 4~5 and volume fraction of 5%~10% at 40~60℃ for 1~2 h to obtain the modified sheet-like filler.

[0010] S2. Mix the modified sheet filler with ethylene glycol at a ratio of 1g:40~60mL until homogeneous. Add sodium acetate, ferric chloride hexahydrate, and polyethylene glycol in sequence and stir until homogeneous. Transfer the mixture to a reactor and control the filling degree to 60%~80%. Place the reactor at 200~250℃ for hydrothermal reaction for 8~12h to allow the ferric oxide magnetic particles to grow in situ and anchor on the surface of the modified sheet filler. After the reaction is complete, filter and wash the mixture in sequence, and place it at 60~80℃ for vacuum drying for 12~24h to obtain the magnetic filler.

[0011] S3. Disperse the magnetic filler in an organic solvent, then mix it evenly with organic resin and curing agent. After degassing for 10-20 minutes under a vacuum of -0.09MPa to -0.1MPa, apply it to the surface of the substrate to be protected. Immediately place the coated substrate in the electromagnetic field generated by the solenoid and let it stand for 2 hours to allow the magnetic filler to be horizontally oriented inside the coating. After curing, a magnetic field-oriented anti-corrosion coating is obtained. The resulting coating forms a continuous horizontally oriented labyrinth barrier structure inside, which can effectively extend the diffusion path of corrosive media and has excellent anti-corrosion performance.

[0012] Furthermore, the sheet filler in step S1 is glass flakes or basalt flakes, with a thickness of 1~2μm and a diameter of 50~100μm. Sheet fillers within this size range can form continuous barrier paths within the coating without causing a decrease in the surface smoothness or adhesion of the coating due to excessively large sheet diameters.

[0013] Furthermore, the concentrated alkaline solution in step S1 is a 2-4 mol / L sodium hydroxide solution; this concentration of sodium hydroxide solution can react with the silica component in the sheet filler to etch a uniform micro-nano-level rough structure on the filler surface, which can improve the grafting rate and grafting stability of the silane coupling agent, and also enhance the anchoring firmness of the subsequently in-situ grown iron oxide particles, preventing the magnetic particles from falling off during mixing and coating.

[0014] Furthermore, the silane coupling agent in step S1 is any one of KH550, KH560, KH570 or KH590; this type of silane coupling agent can form a covalent bond bridging structure between the inorganic sheet filler and the organic resin, improve the interfacial bonding strength between the two phases, avoid interfacial gaps between the filler and the resin matrix, reduce the porosity of the coating, and reduce the diffusion channels of corrosive media.

[0015] Furthermore, in step S2, the mass ratio of ferric chloride hexahydrate to modified sheet filler is 1:1 to 2:1, the mass ratio of sodium acetate to ferric chloride hexahydrate is 3:1 to 5:1, the amount of polyethylene glycol added is 0.5% to 1% of the volume of ethylene glycol, and the average particle size of the in-situ grown magnetite magnetic particles in step S2 is 150 to 200 nm. This raw material ratio can ensure that the loading of magnetite particles on the surface of sheet filler is uniform and controllable, and the loading rate can reach 20% to 30%. Magnetite particles in this particle size range have both excellent magnetic response performance and anchoring firmness, so that all magnetic fillers have stable and consistent magnetic response performance, avoiding the problem of insufficient magnetic response and inability to orient local fillers.

[0016] Furthermore, in step S2, the mixing process is carried out by ultrasonic dispersion for 0.5 h, mechanical stirring for 5-15 min, and ultrasonic dispersion again for 0.5 h. After adding sodium acetate, ferric chloride hexahydrate, and polyethylene glycol, mechanical stirring is performed for 10-20 min. The dispersion method of combining ultrasonic dispersion with mechanical stirring can prevent the agglomeration of the sheet-like filler and ensure that the surface of each filler can fully contact the reactants, thereby achieving uniform in-situ growth of ferric oxide particles.

[0017] Furthermore, in step S3, the solenoid has 600-700 turns per unit length, a working current of 5.2A, and an internal working temperature 10-15°C higher than the ambient temperature. Under this parameter combination, the magnetic field strength generated by the solenoid is higher than the minimum critical magnetic field required for effective deflection of the magnetic filler, which can achieve horizontal directional arrangement of the magnetic filler inside the coating. At the same time, the 10-15°C gentle temperature rise generated by the solenoid can reduce the viscosity of the resin system, reduce the deflection resistance of the magnetic filler, and accelerate the curing of the coating, thus avoiding the settling of the filler or the repositioning of the directional structure during the curing process.

[0018] Furthermore, the organic solvent in step S3 is anhydrous ethanol or acetone, and the dispersion concentration of the magnetic filler in the organic solvent is 0.1~0.5 g / mL, and the dispersion method is ultrasonic dispersion for 10~30 min; these dispersion parameters can ensure that the magnetic filler is fully monodispersed in the organic solvent, avoid filler agglomeration defects when mixed with resin in the later stage, and make the filler distribution inside the coating uniform.

[0019] Furthermore, in step S3, the organic resin is a bisphenol A type waterborne epoxy resin or a solvent-based epoxy resin, the curing agent is a polyamide curing agent, the mass ratio of the curing agent to the epoxy resin is 1:3 to 1:5, and the amount of magnetic filler added is 5% to 15% of the mass of the organic resin. This type of epoxy resin and curing agent system has good reaction compatibility with silane coupling agents, and can form a dense three-dimensional cross-linked network, which improves the coating's resistance to salt spray and ultraviolet radiation, making it suitable for complex marine service environments.

[0020] Furthermore, in step S3, the dry film thickness of the coating after coating is 80~120μm, and the coating method is brush coating, roller coating or high-pressure air spraying. In step S3, the substrate is placed in an electromagnetic field within 1 minute after coating is completed. The coating within this thickness range can meet the long-term anti-corrosion requirements in the marine environment, and will not increase the construction difficulty or reduce the adhesion due to excessive coating thickness. Multiple coating methods can flexibly adapt to the construction requirements of marine metal components of different shapes and in different scenarios. The transfer time requirement within 1 minute can avoid the pre-curing of the coating surface after coating, and ensure that the magnetic filler has sufficient rotation space to achieve directional arrangement.

[0021] The present invention has the following beneficial effects:

[0022] This invention employs a technique of pretreating sheet-like fillers with alkaline etching, modifying them with a silane coupling agent, and then hydrothermally growing magnetite particles in situ. This technique not only improves the anchoring strength between the magnetite particles and the sheet-like fillers, preventing the magnetic components from detaching during coating preparation and application, but also constructs a covalent bond bridging structure between the filler and the organic resin, reducing the interfacial porosity within the coating. This effectively solves the problems of poor magnetic load stability, weak interfacial bonding between the filler and the resin, and easy penetration of corrosive media along the interface in existing technologies.

[0023] This invention, through optimizing solenoid operating parameters, limiting the particle size range of in-situ grown magnetic particles, and clarifying the time interval between coating and magnetic field treatment, ensures that the magnetic filler has stable and consistent magnetic response performance, reduces the deflection resistance of the filler in the resin system, avoids the pre-curing of the coating surface hindering the orientation of the filler after coating, improves the uniformity of filler orientation, and forms a continuous horizontal labyrinth barrier structure inside the coating, effectively extending the diffusion path of corrosive media. It solves the problems of insufficient magnetic response, low orientation rate, and incomplete barrier effect of fillers in the prior art.

[0024] The preparation process of this invention is compatible with conventional epoxy resin curing systems and can be used with various mainstream construction methods such as brushing, roller coating, and high-pressure air spraying. No additional large-scale special equipment is required. It can meet the anti-corrosion construction needs of marine engineering steel structures, port machinery, and rail transit steel structures with various complex shapes. It has excellent long-term protective performance in harsh corrosive environments with high salt spray, high humidity, and strong ultraviolet radiation, and has high industry promotion value. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of silane-coupled magnetic particles, as proposed in this invention.

[0026] Figure 2 This is a SEM image of GFs@Fe3O4 proposed in this invention;

[0027] Figure 3 This is the particle size distribution diagram of Fe3O4 proposed in this invention;

[0028] Figure 4 This is a schematic diagram of the cross-section of the solenoid coil proposed in this invention;

[0029] Figure 5 (a, b, c) are respectively a physical diagram of the solenoid coil, a magnetic scale filler, and a parallel arrangement mechanism diagram proposed in this invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] The specific steps in this embodiment are as follows:

[0033] S1. Glass flakes with a thickness of 1 μm and a diameter of 50 μm were selected as sheet-like fillers. Etching was performed at 60°C for 30 min using a 2 mol / L concentrated sodium hydroxide solution. After rinsing with deionized water until the washing solution was neutral, a 5% (v / v) KH550 silanol aqueous solution with a pH of 4 was prepared. The etched glass flakes were then modified at 40°C for 1 h to obtain modified glass flakes. This alkaline etching step can etch a uniform micro-nano rough structure on the surface of the glass flakes, improving the grafting rate of the silane coupling agent and the subsequent anchoring strength of the magnetic particles, thus solving the defect of easy detachment of magnetic particles in the prior art. Silane modification can construct a covalent bond bridging structure between the inorganic filler and the organic resin, solving the defect of weak interfacial bonding.

[0034] S2. Modified glass flakes and ethylene glycol are mixed at a material-to-liquid ratio of 1g:40mL. The mixture is then dispersed uniformly by ultrasonic dispersion for 0.5h, mechanical stirring for 5min, and ultrasonic dispersion again for 0.5h. Ferric chloride hexahydrate is added at a mass ratio of 1:1 to modified glass flakes, followed by sodium acetate at a mass ratio of 3:1 to ferric chloride hexahydrate. Polyethylene glycol is added at a ratio of 0.5% of the volume of ethylene glycol. After mechanical stirring for 10min, the mixture is transferred to a reactor. The reactor is filled to 60% and subjected to hydrothermal reaction at 200℃ for 8h to allow the ferric oxide magnetic particles to grow in situ and anchor on the surface of the modified glass flakes. After the reaction, the mixture is washed three times by filtration with deionized water and anhydrous ethanol, and then vacuum dried at 60℃ for 12h to obtain the magnetic filler. In this embodiment, the average particle size of the in-situ grown ferric oxide magnetic particles is 150nm. The iron oxide particles grown in situ in this step have a much stronger anchoring strength than those grown by physical adsorption, and the particle size is moderate, which also has excellent magnetic response performance, thus solving the defect of insufficient magnetic response in the existing technology.

[0035] S3. Disperse the magnetic filler in anhydrous ethanol at a concentration of 0.1 g / mL. After ultrasonic dispersion for 10 min, mix it evenly with bisphenol A type waterborne epoxy resin and polyamide curing agent. The mass ratio of curing agent to epoxy resin is 1:3. The amount of magnetic filler added is 5% of the mass of organic resin. After defoaming under a vacuum of -0.09 MPa for 10 min, apply it to the surface of sandblasted Q235 steel substrate by high-pressure air spraying. The dry film thickness of the coating is 80 μm. Within 30 s after coating, place the substrate in the electromagnetic field generated by a solenoid with 600 turns / m per unit length and a working current of 5.2 A. The internal working temperature of the solenoid is 10℃ higher than the ambient temperature. Let it stand for 2 h to allow the magnetic filler to be horizontally oriented inside the coating. After curing, a magnetic field-oriented anti-corrosion coating is obtained. The magnetic field strength generated by the solenoid in this step is higher than the minimum critical magnetic field of 1.32mT required for effective deflection of the scales, which can ensure that the filler is fully oriented. The transfer within 1 minute can avoid the coating pre-curing hindering the deflection of the filler, thus solving the defect of poor orientation uniformity in the existing technology.

[0036] Example 2

[0037] The specific steps in this embodiment are as follows:

[0038] S1. Basalt flakes with a thickness of 2μm and a diameter of 100μm were selected as sheet fillers. They were etched at 80℃ for 60min using a 4mol / L sodium hydroxide concentrated alkaline solution. After rinsing with deionized water until the washing solution was neutral, a KH560 silanol aqueous solution with a pH of 5 and a volume fraction of 10% was prepared. The etched basalt flakes were then modified at 60℃ for 2h to obtain modified basalt flakes.

[0039] S2. Modified basalt flakes and ethylene glycol were mixed at a material-to-liquid ratio of 1g:60mL. The mixture was then dispersed uniformly by ultrasonic dispersion for 0.5h, mechanical stirring for 15min, and ultrasonic dispersion again for 0.5h. Ferric chloride hexahydrate was added at a mass ratio of 2:1 to modified basalt flakes, followed by sodium acetate at a mass ratio of 5:1 to ferric chloride hexahydrate. Polyethylene glycol was added at a ratio of 1% of the volume of ethylene glycol. After mechanical stirring for 20min, the mixture was transferred to a reactor. The reactor was filled to 80% and subjected to hydrothermal reaction at 250℃ for 12h to allow the ferric oxide magnetic particles to grow in situ and anchor on the surface of the modified basalt flakes. After the reaction was completed, the mixture was washed three times by filtration with deionized water and anhydrous ethanol, and then vacuum dried at 80℃ for 24h to obtain the magnetic filler. In this embodiment, the average particle size of the in-situ grown ferric oxide magnetic particles was 200nm.

[0040] S3. Disperse the magnetic filler in acetone to a concentration of 0.5 g / mL. After ultrasonic dispersion for 30 min, mix it evenly with solvent-based epoxy resin and polyamide curing agent. The mass ratio of curing agent to epoxy resin is 1:5. The amount of magnetic filler added is 15% of the mass of organic resin. After defoaming under a vacuum of -0.1 MPa for 20 min, coat it onto the surface of sandblasted Q235 steel substrate by roller coating. The dry film thickness of the coating is 120 μm. Within 45 s after coating, place the substrate in the electromagnetic field generated by a solenoid with 700 turns / m per unit length and a working current of 5.2 A. The working temperature inside the solenoid is 15℃ higher than the ambient temperature. Let it stand for 2 h to allow the magnetic filler to be horizontally oriented inside the coating. After curing, a magnetic field-oriented anti-corrosion coating is obtained.

[0041] Example 3

[0042] The specific steps in this embodiment are as follows:

[0043] S1. Select glass flakes with a thickness of 1.5 μm and a diameter of 75 μm as sheet fillers. Etch with 3 mol / L sodium hydroxide concentrated alkaline solution at 70℃ for 45 min. After rinsing with deionized water until the washing solution is neutral, prepare a KH570 silanol aqueous solution with a pH of 4.5 and a volume fraction of 7.5%. Modify the etched glass flakes at 50℃ for 1.5 h to obtain modified glass flakes.

[0044] S2. Modified glass flakes and ethylene glycol are mixed at a material-to-liquid ratio of 1g:50mL. The mixture is then dispersed uniformly by ultrasonic dispersion for 0.5h, mechanical stirring for 10min, and ultrasonic dispersion again for 0.5h. Ferric chloride hexahydrate is added at a mass ratio of 1.5:1 to modified glass flakes, followed by sodium acetate at a mass ratio of 4:1 to ferric chloride hexahydrate. Polyethylene glycol is added at a ratio of 0.75% of the ethylene glycol volume. After mechanical stirring for 15min, the mixture is transferred to a reactor. The reactor is filled to 70%, and the mixture is subjected to hydrothermal reaction at 225℃ for 10h to allow the ferric oxide magnetic particles to grow in situ and anchor onto the surface of the modified glass flakes. After the reaction, the mixture is washed three times with deionized water and anhydrous ethanol, and then vacuum dried at 70℃ for 18h to obtain the magnetic filler. The loading state and particle size parameters of the in-situ grown ferric oxide magnetic particles in this embodiment are as follows: Figure 2 , Figure 3 As shown. Among them. Figure 2 It can be observed that the iron oxide particles are uniformly embedded in the micro-nano etched pits on the surface of the glass flakes, without agglomeration or large exposed areas, and the anchoring state is stable. Figure 3 Using ImageJ software, the average particle size of the particles in the SEM images was statistically determined to be 177 nm. Ferric oxide particles within this size range exhibit both excellent magnetic response performance and anchoring stability, overcoming the shortcomings of existing technologies such as easy detachment of magnetic particles and poor magnetic response stability.

[0045] S3. Disperse the magnetic filler in anhydrous ethanol at a concentration of 0.3 g / mL. After ultrasonic dispersion for 20 min, mix it evenly with bisphenol A type waterborne epoxy resin and polyamide curing agent. The mass ratio of curing agent to epoxy resin is 1:4. The amount of magnetic filler added is 10% of the mass of organic resin. After defoaming under a vacuum of -0.095 MPa for 15 min, apply it to the surface of sandblasted Q235 steel substrate by brushing. The dry film thickness of the coating is 100 μm. Within 50 s after coating, place the substrate in the electromagnetic field generated by a solenoid with 650 turns / m per unit length and a working current of 5.2 A. The internal working temperature of the solenoid is 12℃ higher than the ambient temperature. Let it stand for 2 h to allow the magnetic filler to be horizontally oriented inside the coating. After curing, a magnetic field-oriented anti-corrosion coating is obtained.

[0046] The schematic diagram of the solenoid coil cross-section used in this step is shown below. Figure 4 As shown, in this embodiment, the coil has a total of 60 turns, a length of 0.09m, and an internal radius of 0.053m. The coating is placed at the center of the solenoid. The transmission and distribution mechanism of the magnetic force in this step can be verified by the following theoretical model: the horizontal steady magnetic field generated by the solenoid covers the entire coating area in the form of a non-contact field, which is a direct action of the field force, requiring no transmission medium and without step-by-step loss. The magnetic field calculation formula for a finite-length solenoid is used: It is the permeability of free space ( ), is the magnetic field strength of the solenoid coil (T), Z is the length from the center of the solenoid (m), I is the magnitude of the current in the coil (A), and R is the inner radius of the coil; where Following the equation: Where N is the number of turns per unit length of the solenoid coil, and L is the length of the solenoid (m); the magnetic field strength in the coating placement area of ​​this embodiment is calculated to be 2.82mT. The field strength distribution within the area is uniform, ensuring that the magnetic field environment of the scales at different locations is consistent, and there is no problem of insufficient local field strength, thus completing the uniform transmission of magnetic force. Further verification of the rationality of force distribution is achieved through a series of force balance formulas for a single scale: in this scheme, the iron oxide on the surface of each magnetic filler is grown in situ, and the difference in load and magnetic saturation intensity is less than 8%, as confirmed by the magnetic torque formula. Viscous torque formula Calculations show that the magnetic torque... middle, It is the vacuum permeability. It is the magnetic susceptibility of particles, reflecting the ease with which a material can be magnetized by a magnetic field. , , These are the characteristic dimensions that describe the geometry of the particles. It is the strength of the applied magnetic field. The angle between the direction of the magnetic field and the long axis of the particle. This determines the trend of torque changing with angle; viscous torque. middle, It is the dynamic viscosity of the surrounding fluid. It is the volume of the particle. It is a shape correction factor. The value represents the angular velocity of the particle rotation. The negative sign indicates that the drag torque is opposite to the direction of rotation. The minimum critical magnetic field required for the scales to deflect is only 1.32 mT, which is far lower than the actual working field strength. The magnetic torque on all scales is greater than the viscous drag torque, and the gravitational torque is 6 orders of magnitude smaller than the viscous torque and can be ignored. Therefore, each scale can obtain sufficient rotational torque to achieve horizontal orientation, effectively avoiding the defects of insufficient magnetic response and uneven orientation of some fillers in the existing technology.

[0047] Comparative Example

[0048] This comparative example uses the existing mainstream magnetic field-oriented anti-corrosion coating preparation process, and the specific steps are as follows:

[0049] Glass flakes with a thickness of 1.5 μm and a diameter of 75 μm were selected as fillers. Without alkaline etching or silane modification, the glass flakes were directly mixed with iron oxide powder (average particle size 180 nm) and KH550 at a mass ratio of 1:0.2:0.05 and stirred for 30 min to obtain a filler with physically loaded magnetic particles. The above filler was then mixed uniformly with bisphenol A type waterborne epoxy resin and a polyamide curing agent at a mass ratio of 10:100:25. After defoaming under a vacuum of -0.095 MPa for 15 min, the mixture was brushed onto the surface of a sandblasted Q235 steel substrate, achieving a dry film thickness of 100 μm. Within 50 s of coating, the substrate was placed in a solenoid electromagnetic field with the same parameters as in Example 3 and allowed to stand for 2 h for curing to obtain a comparative coating.

[0050] Explanation of core reaction equations and corresponding defects

[0051] The reaction equation for the alkaline etching stage is: This reaction can dissolve the silica component on the surface of the sheet-like filler, forming a uniform micro-nano-level rough surface, which provides more active sites for silane coupling agent grafting and iron oxide particle anchoring, effectively solving the defects of low physical adsorption strength and easy detachment of magnetic particles in the existing technology.

[0052] During the silane coupling agent grafting stage, taking KH550 as an example, the hydrolyzed silanol groups undergo a dehydration condensation reaction with the hydroxyl groups on the filler surface. The reaction formula can be expressed as: The amino group at the other end of the silane can undergo a ring-opening reaction with the epoxy group of the epoxy resin to form a covalent bond, thus constructing a stable bridging structure between the inorganic filler and the organic resin. This effectively solves the defect of weak interfacial bonding between the filler and the resin in the existing technology, which easily leads to porosity.

[0053] The reaction equation for the hydrothermal synthesis of iron(III) oxide is as follows: During the reaction, ferric ions are partially reduced to ferrous ions by ethylene glycol. In the weakly alkaline environment provided by the hydrolysis of sodium acetate, ferric oxide is crystallized to form iron(II,III) oxide, which is embedded in the micro-nano rough structure on the surface of the modified filler in situ. The anchoring firmness is more than 15 times higher than that of physical adsorption, effectively solving the defects of easy detachment of magnetic particles and poor magnetic response stability in the existing technology.

[0054] Performance test results and analysis

[0055] Table 1 Core Performance Parameters of Magnetic Packing

[0056] Example 1 21.3 2.1 12.7 Example 2 28.7 1.6 16.3 Example 3 25.2 1.8 14.5 Comparative Example 18.5 27.4 8.9

[0057] The stirring conditions tested in this table are commonly used process parameters in the coating preparation stage. The results show that the loading rate of iron oxide in Examples 1-3 is stable at over 20%, the particle shedding rate is less than 2.2%, and the magnetic saturation intensity is much higher than that of the comparative example. This indicates that the anchoring strength of the in-situ grown magnetic particles is far superior to that of the physical adsorption method in the prior art, effectively solving the defects of poor magnetic load stability and insufficient magnetic response in the prior art.

[0058] Table 2 Core Performance Parameters of Anti-corrosion Coating

[0059] Example 1 91.2 0.32 2280 <![CDATA[2.1 10 -11 ]]> Example 2 93.7 0.27 2670 <![CDATA[1.3 10 -11 ]]> Example 3 92.5 0.29 2450 <![CDATA[1.7 10 -11 ]]> Comparative Example 57.3 1.86 860 <![CDATA[3.2 10 -9 ]]>

[0060] The filler orientation rate in this table was obtained through cross-sectional observation using scanning electron microscopy. The neutral salt spray test followed the GB / T10125-2021 standard, and the corrosion current density was obtained using an electrochemical workstation. In the comparative example, 27.4% of the magnetic particles detached during the coating stirring process, causing some filler to lose its magnetic response capability, resulting in an orientation rate of only 57.3%. The results show that the filler orientation rates of Examples 1-3 are all higher than 90%, the porosity is much lower than that of the comparative example, the salt spray rust-free time is 2.6-3.1 times that of the comparative example, and the corrosion current density is two orders of magnitude lower than that of the comparative example. This indicates that the coating filler prepared by the technical solution of this invention has significantly improved the orientation uniformity, the interface bonding is denser, and the labyrinth barrier effect is fully utilized, effectively solving the defects of low orientation rate, numerous interface pores, and insufficient anti-corrosion performance in the prior art.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of magnetic particles mediated by silane coupling, characterized in that, Includes the following steps: S1. The sheet-like filler is etched with concentrated alkaline solution at 60~80℃ for 30~60 min. After cleaning until neutral, the etched sheet-like filler is modified with a silanol aqueous solution with pH 4~5 and volume fraction of 5%~10% at 40~60℃ for 1~2 h to obtain the modified sheet-like filler. S2. Mix the modified sheet filler with ethylene glycol at a ratio of 1g:40~60mL until homogeneous. Add sodium acetate, ferric chloride hexahydrate, and polyethylene glycol in sequence and stir until homogeneous. Transfer the mixture to a reactor and control the filling degree to 60%~80%. Place the reactor at 200~250℃ for hydrothermal reaction for 8~12h. After the reaction is completed, filter and wash the mixture in sequence, and place it at 60~80℃ for vacuum drying for 12~24h to obtain the magnetic filler. S3. Disperse the magnetic filler in an organic solvent, then mix it evenly with organic resin and curing agent. After degassing for 10 to 20 minutes under a vacuum of -0.09 MPa to -0.1 MPa, apply it to the surface of the substrate to be protected. Immediately place the coated substrate in the electromagnetic field generated by the solenoid and let it stand for 2 hours. After curing, a magnetic field-oriented anti-corrosion coating is obtained.

2. The method for preparing a magnetic field-oriented anti-corrosion coating based on the in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, The sheet-like filler in step S1 is glass flakes or basalt flakes, with a thickness of 1~2μm and a diameter of 50~100μm.

3. The method for preparing a magnetic field-oriented anti-corrosion coating based on the in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, The concentrated alkaline solution in step S1 is a 2-4 mol / L sodium hydroxide solution.

4. The method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, The silane coupling agent in step S1 is any one of KH550, KH560, KH570 or KH590.

5. The method for preparing a magnetic field-oriented anti-corrosion coating based on the in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, In step S2, the mass ratio of ferric chloride hexahydrate to modified sheet filler is 1:1 to 2:1, the mass ratio of sodium acetate to ferric chloride hexahydrate is 3:1 to 5:1, the amount of polyethylene glycol added is 0.5% to 1% of the volume of ethylene glycol, and the average particle size of the in-situ grown magnetite magnetic particles in step S2 is 150 to 200 nm.

6. The method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, In step S2, the mixing process is carried out by ultrasonic dispersion for 0.5 h, mechanical stirring for 5-15 min, and ultrasonic dispersion again for 0.5 h. After adding sodium acetate, ferric chloride hexahydrate, and polyethylene glycol, mechanical stirring is performed for 10-20 min.

7. The method for preparing a magnetic field-oriented anti-corrosion coating based on the in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, In step S3, the solenoid has 600-700 turns per unit length, a working current of 5.2A, and an internal working temperature 10-15°C higher than the ambient temperature.

8. The method for preparing a magnetic field-oriented anti-corrosion coating based on the in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, The organic solvent in step S3 is anhydrous ethanol or acetone, and the magnetic filler is dispersed at a concentration of 0.1~0.5 g / mL in the organic solvent by ultrasonic dispersion for 10~30 min.

9. The method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, The organic resin in step S3 is a bisphenol A type waterborne epoxy resin or a solvent-based epoxy resin, the curing agent is a polyamide curing agent, the mass ratio of the curing agent to the epoxy resin is 1:3 to 1:5, and the amount of magnetic filler added is 5% to 15% of the mass of the organic resin.

10. The method for preparing a magnetic field-oriented anti-corrosion coating by in-situ growth of silane-coupled magnetic particles according to claim 1, characterized in that, In step S3, the dry film thickness of the coating after coating is 80~120μm, and the coating method is brush coating, roller coating or high-pressure air spraying. In step S3, the substrate is placed in an electromagnetic field within 1 minute after coating is completed.

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