Corrosion-resistant magnetic isolation coating material and preparation method thereof

Abstract

The invention relates to the related technical field of multifunctional magnetic materials, in particular to a corrosion-resistant magnetic isolation coating material and a preparation method thereof.The key electromagnetic parameters and corrosion resistance of the material can be controlled mainly through coating modification of nickel ferrite and coating regulation and control of a corrosion-resistant medium, and the relatively optimal comprehensive performance is obtained; on the basis, the modified nickel ferrite and polyurethane resin are compounded to construct a corrosion-resistant magnetic isolation coating, so that the purpose of magnetic protection in a severe corrosion environment is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field related to multifunctional magnetic materials, and in particular to a corrosion-resistant magnetic isolation coating material and a preparation method thereof. Background Art

[0002] In the fields of electronic equipment, machinery manufacturing, and shipbuilding and vehicles, some core electronic devices and facilities are easily affected by magnetic fields and produce electromagnetic disturbances. Therefore, magnetic isolation materials are often required to shield these parts from the magnetic field to maintain the normal operation of electronic facilities and equipment and avoid magnetic field interference.

[0003] Nickel ferrites are widely used in magnetic isolation due to their high magnetic permeability, low coercivity, and low remanence. Publication No. CN104876563A, a 2015 technical proposal by Cheng Kaifen, proposes a ferrite magnetic isolation material with high resistance. This high magnetic resistivity allows it to polarize magnetic lines of force.

[0004] However, traditional nickel ferrite materials have obvious defects. In humid atmospheric environments, especially marine corrosion environments, they are extremely susceptible to corrosion by factors such as chloride ions and humidity, which leads to a decline in material performance and a shortened service life, greatly limiting their application in humid and hot areas, marine and coastal environments. Publication No.: CN215956974U is a 2021 public technical proposal of Suzhou Geyou Micromagnetic Materials Co., Ltd., which proposes a nanocrystalline magnetic isolation material with magnetic field and electromagnetic wave isolation functions. It uses a copper foil layer as a substrate and an iron silicon aluminum material as an electromagnetic wave isolation layer. However, the copper foil is extremely susceptible to oxidation and corrosion in the corrosion field and is not suitable for coastal or humid and hot corrosion scenarios.

[0005] Furthermore, existing magnetic isolation materials are mostly applied in the form of devices or patches. The processing is often complex and involves multiple steps. The high cost of raw materials not only increases the difficulty of production but also makes large-scale production expensive, making industrialization difficult. The coating has excellent workability and can be sprayed onto the exterior of the equipment or facilities to be protected. The simple process not only expands application scenarios but also reduces application costs.

[0006] Publication No. CN118366743B describes a rare earth permanent magnet diffusion source slurry, its preparation method, and its application. The rare earth permanent magnet comprises a neodymium iron boron magnet and a coating layer applied to the surface of the neodymium iron boron magnet. The coating layer is formed by coating the rare earth permanent magnet diffusion source slurry. The rare earth permanent magnet diffusion source slurry contains a reducing resin that can encapsulate heavy rare earth metal powder, preventing it from oxidizing upon contact with air. However, this solution fails to balance the material's electromagnetic shielding performance (magnetic isolation) and environmental adaptability (corrosion resistance), requires high process control, and is difficult to commercialize.

[0007] Therefore, developing a coating material and its preparation method that can significantly improve the corrosion resistance of nickel ferrite, have excellent magnetic isolation effect, and meet the needs of low-cost large-scale production has become a technical problem that needs to be solved urgently. Summary of the Invention

[0008] In view of this, the present invention aims to propose a corrosion-resistant magnetic isolation coating material and a preparation method thereof, which solves the problems of traditional nickel ferrite materials being susceptible to oxidation corrosion in humid atmospheres, low production efficiency and high cost.

[0009] The present invention utilizes the polymerization reaction initiated by pyrrole monomer under the action of an oxidant to coat the surface of nickel ferrite with a polymer layer, and then converts the polymer layer into a carbon layer through a high-temperature carbonization process, thereby optimizing the corrosion resistance of nickel ferrite. The modified nickel ferrite powder has excellent magnetic permeability and low coercive force, can conduct magnetic field in the magnetic field to suppress transmission, and retains low remanence after the magnetization process to avoid self-magnetization, so it has excellent magnetic isolation effect. For magnets with surface magnetic strength below 100Gs, the best magnetic isolation effect can reach more than 70%. At the same time, combined with the relevant theories and mechanisms of composite design, a carbon layer-coated modified nickel ferrite magnetic isolation agent is designed. On this basis, a polyurethane adhesive is compounded to prepare a magnetic isolation coating material, which can maintain good magnetic isolation effect in extreme environments. The coating material itself, which is prepared by mixing key filling powder and polyurethane resin, has excellent anti-corrosion effect. After 1000 hours of salt spray test, the coating can still maintain no cracking, falling off, or rust. It can be applied to humid atmospheric environment and marine corrosion application environment, reducing the interference of external magnetic field on the protected equipment or reducing the interference of the equipment's own magnetic field on the external human-machine environment. The synthesis mechanism and synthesis process used in the present invention involve simple links, the industrial price of raw materials is low, and can meet low-cost large-scale production and application needs. This technology is suitable for magnetic protection of various equipment, vehicles, ships, and machinery in hot and humid regions, marine environments, or coastal environments, and has broad economic prospects. The corrosion-resistant magnetic isolation coating material prepared using this process is simple to manufacture, has adjustable properties, and exhibits stable corrosion resistance, possessing significant research value and market applications. Furthermore, its principles and synthesis methods can be applied to the corrosion protection modification design of other metallic soft magnetic materials and the design and development of magnetic isolation coating materials.

[0010] The technical solution of the present invention is achieved as follows:

[0011] One object of the present invention is to disclose a corrosion-resistant magnetic isolation coating material, comprising modified soft magnetic material powder and polyurethane resin, wherein:

[0012] The modified soft magnetic material powder is a composite material in which the surface of the soft magnetic material particles is coated with a carbon layer, and the carbon layer is formed by initiating a polymerization reaction on the surface of the soft magnetic material particles to form a polymer layer, which is then converted through a high-temperature carbonization treatment;

[0013] The polyurethane resin acts as a binder to firmly bind the modified soft magnetic material powder together to form a uniform and dense coating structure, which can effectively prevent the invasion of corrosive media and protect the substrate from corrosion.

[0014] Furthermore, the polymer is polypyrrole, and the soft magnetic material is nickel ferrite.

[0015] Furthermore, the particle size of the soft magnetic material is 3-5 microns.

[0016] Furthermore, the coating material has no cracking, falling off or rusting after 1000 hours of testing in a salt spray test. For magnets with a surface magnetic strength below 100 Gs, the best magnetic isolation effect can reach more than 70%.

[0017] Furthermore, the soft magnetic material is one or more of nickel ferrite, iron-cobalt alloy or iron-nickel alloy.

[0018] Another object of the present invention is to disclose a method for preparing a corrosion-resistant magnetic isolation coating material, which comprises the following specific steps:

[0019] S1: Disperse the soft magnetic material powder evenly in deionized water, add p-toluenesulfonic acid and pyrrole monomer, and ensure that all components are fully mixed through mechanical stirring and ultrasonic dispersion;

[0020] S2: preparing an ammonium persulfate solution and slowly adding it dropwise to the mixed solution obtained in step 1, and performing a polymerization reaction for 24 hours by maintaining a mechanical stirring rate of 800 rpm;

[0021] S3: washing the product with ethanol and removing unreacted substances by centrifugation, followed by drying at 60-80°C until the solid is completely dry;

[0022] S4: placing the treated brown powder into a high-temperature tube furnace and calcining it at 800-1200 degrees Celsius under nitrogen or argon protection to complete the conversion from polypyrrole to carbon layer;

[0023] S5: Mix the modified soft magnetic material powder with polyurethane resin, add an appropriate amount of curing agent, and apply it on the magnetic metal substrate through a brush coating process. After natural curing, a corrosion-resistant magnetic isolation coating is formed.

[0024] Furthermore, in step 1, the soft magnetic material is NiFeO4, and every 50g of NiFeO4 powder needs to be dispersed in about 500mL of deionized water, and 15g of p-toluenesulfonic acid and 30-150mL of pyrrole monomer are added.

[0025] Furthermore, in step 2, every 100 g of ammonium persulfate needs to be dissolved in 500 mL of deionized water.

[0026] Furthermore, in step 4, the calcination temperature is increased at a rate of 5° C. / hour and kept at this temperature for 2 hours.

[0027] Furthermore, in step 5, the mass ratio of the modified nickel ferrite to the polyurethane resin is preferably 4:1, wherein the modified nickel ferrite is not less than 8 g and the polyurethane resin is not less than 2 g.

[0028] Compared with the prior art, the corrosion-resistant magnetic isolation coating material and the preparation method thereof of the present invention have the following advantages:

[0029] 1. The corrosion-resistant magnetic isolation coating material and its preparation method proposed in the present invention can significantly improve the corrosion resistance and magnetic isolation effect of nickel ferrite without adding complex process flow. Through simple coating, separation and heat treatment steps, it can maintain excellent protection capabilities in extreme environments, greatly reducing production costs and time, making large-scale production and practical applications more feasible, which is of great significance for improving the protection level of key facilities in the fields of electronic equipment and mechanical manufacturing.

[0030] 2. The present invention optimizes the electromagnetic parameters and corrosion resistance of the modified nickel ferrite powder by finely controlling the thickness of the carbon layer converted from the polymer layer on the surface of the nickel ferrite, and compounds it with a polyurethane resin to construct a corrosion-resistant magnetic isolation coating, thereby effectively solving the problem that traditional nickel ferrite materials are susceptible to corrosion in humid atmospheres, especially in marine corrosion environments. At the same time, it avoids the use of expensive and complex anti-corrosion treatment technologies, improves the overall performance of the coating material, reduces the demand for external environment simulation equipment, simplifies the testing process, and provides a more stable and reliable protection effect.

[0031] 3. This invention utilizes a systematic synthesis mechanism and process design approach. By precisely controlling the raw materials at different addition ratios, it effectively regulates the particle size and micromorphology of the final product. This facilitates a deeper understanding of the properties of corrosion-resistant, magnetic-isolating coating materials and improves the ability to predict and customize the desired material properties for specific applications. Furthermore, because the reaction mechanism and process flow involved in this method are simple and easy to adjust and replicate, it can be readily applied to the modification of other types of soft magnetic materials and the design and development of novel coating materials, demonstrating broad application prospects and technological promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 This is a scanning electron microscope image of the modified nickel ferrite-1 of Example 1;

[0034] Figure 2 This is a scanning electron microscope image of the modified nickel ferrite-2 of Example 2;

[0035] Figure 3 This is a scanning electron microscope image of the modified nickel ferrite-3 of Example 3;

[0036] Figure 4 This is a scanning electron microscope image of the modified nickel ferrite-4 of Example 4;

[0037] Figure 5 This is a scanning electron microscope image of the modified nickel ferrite-5 of Example 5;

[0038] Figure 6 is the magnetic intensity of the modified nickel ferrite-1 vibration sample of Example 1;

[0039] Figure 7 is the magnetic intensity of the modified nickel ferrite-2 vibration sample of Example 2;

[0040] Figure 8 is the magnetic intensity of the modified nickel ferrite-3 vibration sample of Example 3;

[0041] Figure 9 is the magnetic intensity of the modified nickel ferrite-4 vibration sample of Example 4;

[0042] Figure 10 This is the magnetic strength of the modified nickel ferrite-5 vibration sample of Example 5. DETAILED DESCRIPTION

[0043] In order to make the technical means, objectives and effects of the present invention easier to understand, embodiments of the present invention are described in detail below with reference to specific figures.

[0044] It should be noted that all terms used in the present invention to indicate direction and position, such as "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "inside", "outside", "top", "low", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection status between various components in a specific state. They are only for the convenience of describing the present invention, and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they cannot be understood as limiting the present invention. In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features.

[0045] In the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical connections; direct connections or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0046] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] An object of the present invention is to disclose a corrosion-resistant magnetic isolation coating material, comprising modified nickel ferrite powder and polyurethane resin, wherein:

[0048] The modified nickel ferrite powder is a composite material in which the surface of nickel ferrite particles is coated with a carbon layer. The carbon layer is formed by initiating a polymerization reaction on the surface of the nickel ferrite particles to form a polymer layer, which is then converted through a high-temperature carbonization treatment.

[0049] The polyurethane resin acts as a binder to firmly bind the modified nickel ferrite powder together to form a uniform and dense coating structure, which can effectively prevent the invasion of corrosive media and protect the substrate from corrosion.

[0050] Modified nickel ferrite powder is a composite structure with nickel ferrite particles as its core and a carbon layer coated on the surface. The carbon layer is formed by high-temperature carbonization of a polymer layer, providing both physical isolation and chemical protection, effectively preventing oxidation or degradation of the nickel ferrite in humid or corrosive environments. Furthermore, nickel ferrite itself possesses excellent soft magnetic properties, such as high magnetic permeability and low coercivity, which can effectively shield or guide magnetic fields, achieving a "magnetic isolation" function. Polyurethane resin acts as a binder, tightly bonding a large number of modified nickel ferrite particles together to form a continuous, dense coating structure. This coating structure exhibits excellent adhesion, flexibility, and weather resistance, enhancing the overall mechanical strength and crack resistance of the coating. It also exhibits excellent water and chemical resistance, further preventing external corrosive media such as moisture, salt spray, acids and alkalis from penetrating the substrate surface, achieving a dual protection effect. It can be used in key areas of ships, vessels, coastal facilities, polar equipment, aerospace, electronic communications, and other fields that require both magnetic isolation and corrosion protection. It is particularly suitable for surface protection of magnetic devices in harsh environments such as high humidity, high salt spray, and acid and alkali corrosion.

[0051] The dual protection mechanism of carbon layer + polyurethane resin significantly improves the stability of the material in marine environments, humid and hot areas, and industrial corrosive environments. It not only retains the magnetic properties of nickel ferrite, but also enhances its chemical inertness, solving the problem of easy oxidation of traditional soft magnetic materials. The coating-carbonization-compounding process adopted is simple and controllable, with a wide source of raw materials and low cost, suitable for large-scale production. It can be applied to the surface of the metal substrate by brushing, spraying, etc., and can be put into use after curing, with convenient operation.

[0052] Specifically, the coating material showed no cracking, peeling or rusting after 1,000 hours of testing in a salt spray test. For magnets with a surface magnetic strength below 100 Gs, the optimal magnetic isolation effect can reach more than 70%.

[0053] The coating material exhibits excellent corrosion resistance overall and good magnetic isolation properties. Salt spray testing is a standard method for evaluating the corrosion resistance of materials in marine or high-salt, humid, and hot environments. The 1000-hour corrosion-free period demonstrates that the coating can maintain structural integrity and functionality even in long-term exposure to salt spray. This indicates that the carbon layer on the nickel ferrite surface has excellent chemical stability, while the polyurethane resin, as a dense coating, effectively blocks the penetration of corrosive media such as water vapor and chloride ions. The ability to achieve a magnetic isolation effect of over 70% for low-field (≤100 Gs) magnets demonstrates that the material achieves effective magnetic field attenuation without destroying its intrinsic magnetic response characteristics. This makes it suitable for the weak magnetic field control needs of precision electronic equipment. Many sensors, signal processing modules, and communication equipment experience weak magnetic field interference, requiring local shielding to prevent misoperation or performance degradation.

[0054] Specifically, the nickel ferrite particle size is about 3-5 microns, and the thickness of the carbon layer coated on the surface can be adjusted according to different application requirements to achieve the best balance between magnetic isolation effect and corrosion resistance.

[0055] Nickel ferrite particle size is controlled within the 3-5 micron range, ensuring good dispersion and uniformity of the material, facilitating the formation of a continuous and stable coating structure. By adjusting the amount of raw materials added during the polymerization reaction, such as the amount of pyrrole monomer, the thickness of the carbon layer can be precisely controlled, helping to improve the overall performance consistency of the coating and reduce performance fluctuations caused by material inhomogeneity, ensuring product reliability and stability in actual use. It also improves the coating's adhesion and wear resistance, further enhancing its durability and practicality. Different carbon layer thicknesses affect the final product's magnetic isolation and corrosion resistance, thereby meeting the needs of specific application scenarios.

[0056] This setting can provide a certain degree of protection while maintaining the good magnetic permeability of nickel ferrite, ensuring the material's effective shielding of the magnetic field and significantly improving the material's chemical stability and corrosion resistance. It performs particularly well in harsh environments such as marine environments and acid-base corrosion. The thickness of the carbon layer can be flexibly adjusted to cope with a variety of application scenarios, achieving the best balance between magnetic isolation effect and corrosion resistance.

[0057] Specifically, the modified nickel ferrite magnetic isolation agent uses nickel ferrite as the main functional component. According to the relevant reaction principle, nickel ferrite can be replaced with other types of soft magnetic materials, such as iron-cobalt alloy, iron-nickel alloy, etc.

[0058] Using different types of soft magnetic materials allows the electromagnetic properties of the coating material to be tailored to the needs of specific application scenarios. For example, iron-cobalt alloys have high saturation magnetization, while iron-nickel alloys are known for their excellent magnetic permeability. Different soft magnetic materials have different electromagnetic parameters (such as permeability, coercivity, and remanence). By selecting the right material, it is possible to optimize the magnetic isolation effect or adapt to different magnetic field environments. Due to the unique properties of different soft magnetic materials, this technology can be applied to a wider range of scenarios. For example, iron-nickel alloys are used in applications requiring higher permeability, while iron-cobalt alloys are used when high saturation magnetization is required.

[0059] By selecting appropriate materials, this setting can make the coating suitable for a wider range of working conditions, such as high temperature, high humidity or severe chemical corrosion environments, reducing the cost and difficulty of technology transfer and promotion.

[0060] Specifically, the polymer is polypyrrole.

[0061] As a conductive polymer, polypyrrole itself has certain conductivity and electromagnetic shielding properties. By controlling the coating thickness of polypyrrole, the electromagnetic parameters of the final product, such as magnetic permeability and coercive force, can be fine-tuned, thereby optimizing the magnetic isolation effect and helping to enhance the magnetic isolation properties of the final coating material, especially in application scenarios that require efficient electromagnetic interference protection.

[0062] Polypyrrole (PPy) has excellent solution processability and can be easily coated onto the surface of nickel ferrite particles using a solution method. It also improves interparticle dispersion, prevents agglomeration, and ensures uniformity and consistency of the coating material. By adjusting polymerization conditions such as monomer concentration, initiator dosage, and reaction time, the thickness of the PPy layer can be precisely controlled. Polypyrrole layers of varying thickness form carbon layers of varying thicknesses upon carbonization, achieving an optimal balance between magnetic isolation and corrosion resistance. The carbon layer formed after high-temperature carbonization exhibits high chemical stability and corrosion resistance. This carbon layer effectively blocks the intrusion of moisture, oxygen, and other corrosive media, protecting the nickel ferrite particles within and extending the coating's service life. PPy is also a relatively environmentally friendly material, with a mild and controllable synthesis process that does not require extreme conditions or toxic reagents. Furthermore, its relatively low raw material price and simple production process make it suitable for large-scale industrial production, reducing costs. The carbonized PPy layer not only improves the coating's corrosion resistance but also enhances its mechanical strength and adhesion.

[0063] Another object of the present invention is to disclose a method for preparing a corrosion-resistant magnetic isolation coating material, comprising the following specific steps:

[0064] S1: A certain amount of NiFeO4 powder is finely ground and evenly dispersed in deionized water with sufficient mechanical stirring; p-toluenesulfonic acid and pyrrole monomer are then added, mixed together, and thoroughly ultrasonically dispersed;

[0065] NiFeO4 powder is evenly dispersed in deionized water, and p-toluenesulfonic acid and pyrrole monomer are added. Mechanical stirring and ultrasonic dispersion are used to ensure thorough mixing of the components. Fine grinding and ultrasonic dispersion help break up particle agglomerates, improve the dispersion of the reactants, and provide a uniform reaction environment for the subsequent polymerization reaction, helping to form a continuous and uniform coating layer.

[0066] S2: dissolving ammonium persulfate in deionized water to prepare an ammonium persulfate solution, and slowly adding the solution dropwise to the mixed solution obtained in step 1 while mechanically stirring the mixture at a rate of 800 rpm using a mechanical stirring device for 24 hours;

[0067] Ammonium persulfate, an oxidizing agent, is dissolved in deionized water and slowly added dropwise to a solution containing NiFeO4, p-toluenesulfonic acid, and pyrrole monomer. The polymerization reaction is carried out for 24 hours while maintaining a mechanical stirring rate of 800 rpm. By controlling the polymerization reaction conditions, such as temperature and stirring speed, to ensure that the polypyrrole is evenly coated on the surface of the nickel ferrite, forming a protective film, the thickness of the coating can be effectively controlled, thereby affecting the electromagnetic parameters and corrosion resistance of the final product.

[0068] S3: Pour out the turbid solution obtained in step S2, pour ethanol into the mixture, mechanically stir for 15 minutes, and then centrifuge to separate the solid phase product in the mixed solution. Repeat this centrifugation step, and dry the separated solid phase material at 60-80°C for 24 hours until the solid is completely dry and in the form of black powder;

[0069] This step removes impurities that may affect the quality of the coating and ensures the purity of the final product. Appropriate drying conditions ensure the stability of the material structure and the smooth progress of subsequent high-temperature carbonization.

[0070] S4: The brown powder obtained in step S3 is placed in an alumina crucible, placed in a high-temperature tube furnace, and calcined at 800-1200 degrees Celsius in a nitrogen or argon protective environment at a heating rate of 5°C / hour, and kept warm for 2 hours. After natural cooling, the product is ground to obtain modified nickel ferrite powder;

[0071] The treated brown powder is placed in a high-temperature tube furnace and calcined at 800-1200°C under nitrogen or argon to complete the conversion from polypyrrole to a carbon layer. This high-temperature carbonization transforms the polypyrrole into a chemically inert carbon layer, significantly improving the corrosion resistance of the nickel ferrite. Furthermore, this step allows the thickness of the carbon layer to be adjusted, thereby optimizing the balance between magnetic isolation and corrosion resistance.

[0072] S5: Weigh a certain amount of modified nickel ferrite and polyurethane resin, mix them, stir them thoroughly, add a corresponding proportion of polyurethane curing agent, stir them evenly, and then use a brush coating process to apply the coating on the magnetic metal substrate. Let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating material sample;

[0073] Modified nickel ferrite powder is mixed with polyurethane resin, and an appropriate amount of curing agent is added. The mixture is then applied to a magnetic metal substrate via a brush coating process. After natural curing, a corrosion-resistant, magnetic-isolating coating is formed. Using polyurethane resin as a binder not only enhances the overall strength and stability of the coating, but also effectively prevents the intrusion of external corrosive media. This method is simple and suitable for large-scale production. The coating thickness can be adjusted according to actual needs to meet the requirements of different application scenarios.

[0074] Specifically, in step 1, every 50 g of NiFeO4 powder needs to be dispersed in about 500 mL of deionized water, and 15 g of p-toluenesulfonic acid and 30-150 mL of pyrrole monomer are added.

[0075] 50g of NiFeO4 powder was evenly dispersed in 500mL of deionized water, ensuring uniform distribution of the nickel ferrite particles within the solution, providing a stable dispersion for the subsequent polymerization reaction. p-Toluenesulfonic acid, as part of the catalyst or initiator, helped promote the polymerization of pyrrole monomers on the nickel ferrite surface. It regulates the pH of the reaction environment, thereby affecting the rate and efficiency of the polymerization reaction. Adding varying amounts of pyrrole monomer directly affects the thickness of the resulting polypyrrole layer, and thus the thickness of the carbon layer after carbonization. By adjusting the amount of pyrrole monomer, the thickness of the nickel ferrite surface coating can be controlled, optimizing both magnetic isolation and corrosion resistance.

[0076] This setting can effectively break the agglomeration between nickel ferrite particles, ensuring that each particle can be evenly coated with a polypyrrole layer, improving the consistency and stability of the coating, and precisely controlling the pH of the reaction medium, helping to obtain a high-quality, uniform polymer coating. The performance of the final product can be flexibly adjusted within a certain range, expanding its scope of application.

[0077] Specifically, in step 2, 100 g of ammonium persulfate needs to be dissolved in about 500 mL of deionized water.

[0078] Dissolve 100g of ammonium persulfate in 500mL of deionized water to prepare a solution. As a strong oxidant, ammonium persulfate effectively initiates polymerization of pyrrole monomers, forming a polypyrrole coating on the surface of nickel ferrite. Slowly adding the persulfate in drops allows for controlled reaction rate, allowing the polymerization to proceed evenly throughout the solution. This ensures the consistency and stability of the coating, helps ensure a uniform reaction, and avoids incomplete reactions or side reactions caused by localized high concentrations.

[0079] Specifically, in step 4, the calcination temperature is 800-1200°C, preferably 1000°C.

[0080] Under high temperature conditions, the polypyrrole layer will undergo a pyrolysis reaction and transform into a chemically inert carbon layer, which can enhance the stability of the nickel ferrite particle surface and significantly improve its corrosion resistance. The preferred calcination temperature of 1000°C can minimize the impact on the original magnetic properties of nickel ferrite while ensuring sufficient carbonization, and achieve the best balance between magnetic isolation effect and corrosion resistance.

[0081] By precisely controlling the calcination temperature, this setting can complete the carbonization process without significantly damaging the original magnetic properties of nickel ferrite, helping to maintain the material's excellent magnetic properties such as high magnetic permeability and low coercivity, thereby ensuring the coating material's efficient magnetic isolation effect, enhancing the density and uniformity of the coating's internal structure, and making the coating more firmly adhere to the substrate surface, reducing problems such as cracking and falling off caused by environmental changes, improving the coating's overall protective performance, and greatly simplifying the production process, reducing production costs, and facilitating large-scale industrial production.

[0082] Specifically, in step 5, the mass ratio of the modified nickel ferrite to the polyurethane resin is preferably 4:1, wherein the modified nickel ferrite is not less than 8 g and the polyurethane resin is not less than 2 g.

[0083] Modified nickel ferrite and polyurethane resin are mixed in a mass ratio of 4:1, ensuring that the coating material has both good magnetic isolation effect and excellent mechanical properties and corrosion resistance. The modified nickel ferrite is not less than 8g and the polyurethane resin is not less than 2g, ensuring the effective content of key components in the coating, thereby ensuring that the overall performance of the coating meets the design requirements.

[0084] This setting can ensure that the nickel ferrite content in the coating is high enough to provide the required magnetic isolation effect, while not affecting other physical properties of the coating due to excessive addition. It can ensure that the coating has good adhesion and integrity, avoiding cracking or falling off during use, making the production process more standardized and controllable, reducing unnecessary trial and error costs and time consumption, and lowering production costs.

[0085] Example 1

[0086] The present invention provides a corrosion-resistant magnetic isolation coating material and a preparation method thereof, comprising the following steps:

[0087] Step S1: 50 g of NiFeO4 powder is finely ground and evenly dispersed in 500 mL of deionized water, and then mechanically stirred. 15 g of p-toluenesulfonic acid and 30 mL of pyrrole monomer are then added, mixed together, and ultrasonically dispersed using an ultrasonic machine.

[0088] In step S2, 100 g of ammonium persulfate was dissolved in 500 mL of deionized water to prepare an ammonium persulfate solution, and the solution was slowly added dropwise to the container containing the mixed solution obtained in step S1, while mechanically stirring the mixture at a rate of 800 rpm using a mechanical stirring device for 24 hours.

[0089] In step S3, the turbid solution obtained in step S2 is poured out, 250 ml of ethanol is poured into the mixture, and the mixture is mechanically stirred for 15 minutes, followed by centrifugation to separate the solid phase product in the mixed solution. This centrifugation step only separates the liquid phase from the solid phase. 250 ml of ethanol is poured into the solid phase product again, and the centrifugation step S is repeated. The separated solid phase material is dried at 60-80°C for 24 hours until the solid is completely dry and in the form of a black powder.

[0090] Step S4: The brown powder obtained in step S3 is put into an alumina crucible, placed in a high-temperature tube furnace, and calcined at 1000 degrees Celsius in a nitrogen or argon protective environment at a heating rate of 5°C / hour. The mixture is kept warm for 2 hours, and the product is ground after natural cooling to obtain modified nickel ferrite-1 powder.

[0091] Step S5, weigh 80g of modified nickel ferrite, mix it with 20g of polyurethane resin, stir it thoroughly and evenly, add a polyurethane curing agent of corresponding proportion, stir it evenly and then use a brush coating process to brush the coating onto the magnetic metal substrate, and let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating-1 coating material sample.

[0092] Surface magnetic field testing using a Gauss meter revealed a magnetic field of 82.0 Gs before coating the magnetic metal substrate. After application of the corrosion-resistant magnetic isolation coating -1, the surface magnetic field dropped to 22.7 Gs, achieving a magnetic field isolation efficiency of 71.7%. Salt spray performance testing was also conducted on the sample. After 1000 hours of neutral salt spray testing, the coating surface showed no cracking, peeling, or rust, demonstrating excellent corrosion resistance.

[0093] Example 2

[0094] Step S1: 50 g of NiFeO4 powder is finely ground and evenly dispersed in 500 mL of deionized water, and then mechanically stirred. 15 g of p-toluenesulfonic acid and 60 mL of pyrrole monomer are then added, mixed together, and ultrasonically dispersed using an ultrasonic machine.

[0095] Step S2 is the same as in Example 1.

[0096] Step S3 is the same as in Example 1.

[0097] Step S4: The brown powder obtained in step S3 is put into an alumina crucible, placed in a high-temperature tube furnace, and calcined at 1000 degrees Celsius in a nitrogen or argon protection environment at a heating rate of 5°C / hour. The mixture is kept warm for 2 hours, and the product is ground after natural cooling to obtain modified nickel ferrite-2 powder.

[0098] Step S5, weigh 80g of modified nickel ferrite, mix it with 20g of polyurethane resin, stir it thoroughly and evenly, add the corresponding proportion of polyurethane curing agent, stir it evenly and then use a brush coating process to brush the coating onto the magnetic metal substrate, and let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating-2 coating material sample.

[0099] Surface magnetic field testing using a Gaussmeter revealed a magnetic field of 82.0 Gs before coating, and 30.6 Gs after application of the corrosion-resistant magnetic isolation coating -1, demonstrating a magnetic field isolation effectiveness of 63.0%. Salt spray performance testing was also conducted on the sample. After 1000 hours of neutral salt spray testing, the coating surface showed no cracking, peeling, or rust, demonstrating excellent corrosion resistance.

[0100] Example 3

[0101] Step S1: 50 g of NiFeO4 powder is finely ground and evenly dispersed in 500 mL of deionized water, and then mechanically stirred. 15 g of p-toluenesulfonic acid and 90 mL of pyrrole monomer are then added, mixed together, and ultrasonically dispersed using an ultrasonic machine.

[0102] Step S2 is the same as in Example 1.

[0103] Step S3 is the same as in Example 1.

[0104] Step S4: The brown powder obtained in step S3 is loaded into an alumina crucible, placed in a high-temperature tube furnace, and calcined at 1000 degrees Celsius in a nitrogen or argon protective environment at a heating rate of 5°C / hour. The mixture is kept warm for 2 hours, and the product is ground after natural cooling to obtain modified nickel ferrite-3 powder.

[0105] Step S5, weigh 80g of modified nickel ferrite, mix it with 20g of polyurethane resin, stir it thoroughly and evenly, add the corresponding proportion of polyurethane curing agent, stir it evenly and then use a brush coating process to brush the coating onto the magnetic metal substrate, and let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating-3 coating material sample.

[0106] Surface magnetic field testing using a Gauss meter revealed a magnetic field of 82.0 Gs before coating, and 36.5 Gs after application of the corrosion-resistant magnetic isolation coating -1, demonstrating a magnetic field isolation effectiveness of 55.4%. Salt spray performance testing was also conducted on the sample. After 1000 hours of neutral salt spray testing, the coating surface showed no cracking, peeling, or rust, demonstrating excellent corrosion resistance.

[0107] Example 4

[0108] Step S1: 50 g of NiFeO4 powder was finely ground and evenly dispersed in 500 mL of deionized water, and then mechanically stirred thoroughly. 15 g of p-toluenesulfonic acid and 120 mL of pyrrole monomer were then added, mixed together, and ultrasonically dispersed thoroughly using an ultrasonic machine.

[0109] Step S2 is the same as in Example 1.

[0110] Step S3 is the same as in Example 1.

[0111] Step S4: The brown powder obtained in step S3 is put into an alumina crucible, placed in a high-temperature tube furnace, and calcined at 1000 degrees Celsius in a nitrogen or argon protection environment at a heating rate of 5°C / hour. The mixture is kept warm for 2 hours, and the product is ground after natural cooling to obtain modified nickel ferrite-4 powder.

[0112] Step S5, weigh 80g of modified nickel ferrite, mix it with 20g of polyurethane resin, stir it thoroughly and evenly, add the corresponding proportion of polyurethane curing agent, stir it evenly and then use a brush coating process to brush the coating onto the magnetic metal substrate, and let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating-4 coating material sample.

[0113] A Gaussmeter was used to test the surface magnetic properties of the magnetic metal substrate, showing a magnetic field of 82.0 Gs before coating and 41.4 Gs after application of the Corrosion-Resistant Magnetic Isolation Coating-1, demonstrating a magnetic field isolation efficiency of 49.5%. Salt spray performance testing was also conducted on the sample. After 1000 hours of neutral salt spray testing, the coating surface showed no cracking, peeling, or rust, demonstrating excellent corrosion resistance.

[0114] Example 5

[0115] Step S1: 50 g of NiFeO4 powder is finely ground and evenly dispersed in 500 mL of deionized water, and then mechanically stirred. 15 g of p-toluenesulfonic acid and 150 mL of pyrrole monomer are then added, mixed together, and ultrasonically dispersed using an ultrasonic machine.

[0116] Step S2 is the same as in Example 1.

[0117] Step S3 is the same as in Example 1.

[0118] Step S4: The brown powder obtained in step S3 is put into an alumina crucible, placed in a high-temperature tube furnace, and calcined at 1000 degrees Celsius in a nitrogen or argon protection environment at a heating rate of 5°C / hour. The mixture is kept warm for 2 hours, and the product is ground after natural cooling to obtain modified nickel ferrite-5 powder.

[0119] Step S5, weigh 80g of modified nickel ferrite, mix it with 20g of polyurethane resin, stir it thoroughly and evenly, add the corresponding proportion of polyurethane curing agent, stir it evenly and then use a brush coating process to brush the coating onto the magnetic metal substrate, and let it stand naturally until the coating is completely cured to obtain a corrosion-resistant magnetic isolation coating-5 coating material sample.

[0120] Surface magnetic field testing using a Gaussmeter revealed a magnetic field of 82.0 Gs before coating, and 52.6 Gs after application of the corrosion-resistant magnetic isolation coating -1, demonstrating a magnetic field isolation efficiency of 35.9%. Salt spray performance testing was also conducted on the sample. After 1000 hours of neutral salt spray testing, the coating surface showed no cracking, shedding, or rust, demonstrating excellent corrosion resistance.

[0121] As can be seen from the above examples, the raw materials in the reaction process are distilled water, p-toluenesulfonic acid, pyrrole monomer, ethanol, polyurethane resin, etc. The reaction process and the required equipment are simple, and have mass production conditions and batch application potential.

[0122] The magnetic isolation agent in the corrosion-resistant magnetic isolation coating material presents slightly different particle sizes and microscopic morphologies under the control of different raw material addition ratios during the synthesis process, such as Figure 1 、 2 As shown in the high-magnification scanning electron microscope photos of Figures 3, 4, and 5 with different raw material addition ratios, the basic morphology of the magnetic isolation agent is a single nickel ferrite sheet with a size of about 3-5 microns coated with nano-scale carbon particles on the surface. As the amount of reactants added increases, the number of carbon particles and the coating thickness gradually increase, but the overall morphology characteristics remain basically unchanged.

[0123] The magnetic strength test of the vibration sample of the magnetic isolation agent in the corrosion-resistant magnetic isolation coating material shows a certain change pattern as the coating amount of the carbon layer changes, that is, as the coating amount of the carbon layer increases, the saturation magnetization intensity of the material gradually decreases, such as Figure 6 、 7 As shown in Figures 8, 9, and 10, the saturation magnetization intensity gradually decreases from about 200emu / g to about 60emu / g, proving that the increase in the thickness of the coating layer will cause the magnetic properties of the material to decrease.

[0124] The magnetic isolation effect of the corrosion-resistant magnetic isolation coating is affected by the thickness of the carbon layer coated on the outside of the powder. The thicker the carbon layer, the lower the proportion of nickel ferrite in the components when constructing the coating, resulting in a certain reduction in its magnetic isolation effect. Taking a magnet with a surface magnetic intensity of 82.0Gs as an example, the surface magnetism of the coating material constructed with powder with a smaller amount of carbon coating can be reduced to 22.7Gs, and the magnetic field isolation effect reaches 71.7%. The surface magnetism of the coating material constructed with powder with a larger amount of carbon coating is only reduced to 52.6Gs, and the magnetic field isolation effect reaches 35.9%.

[0125] The magnetic isolation effect of the corrosion-resistant magnetic isolation coating mainly comes from the electromagnetic effect of nickel ferrite. This type of soft magnetic material has good saturation magnetization intensity. Compared with common metal substrates, this type of material has good magnetic flux line conduction effect in the magnetic field, and can guide the magnetic field to propagate laterally in the coating system. At the same time, its vibration magnetic strength test results show that the coercive force is low, which proves that its residual magnetism is low after the action of the magnetic field, and it is not easy to form a derivative magnetic source. Therefore, it has a good weakening and magnetic isolation effect on the external magnetic field. When applied to the outside of the protected object, it can hinder the influence of the magnetic field on the internal object.

[0126] The modified nickel ferrite is composed of nickel ferrite coated with a carbon layer in the final product. The carbon layer is chemically inert and not easily corroded or eroded. The polyurethane resin in the coating raw material plays an adhesive role. The combined coating material is dense inside and can prevent the invasion of corrosive media. Therefore, the material system has good corrosion resistance and can maintain a stable state in a high-temperature environment. It can be used in a hot and humid or salt spray corrosion environment.

[0127] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A corrosion-resistant magnetic isolation coating material, characterized in that: It includes modified soft magnetic material powder and polyurethane resin, wherein: The modified soft magnetic material powder is a composite material in which the surface of the soft magnetic material particles is coated with a carbon layer, and the carbon layer is formed by initiating a polymerization reaction on the surface of the soft magnetic material particles to form a polymer layer, which is then converted through a high-temperature carbonization treatment; The polyurethane resin acts as a binder to firmly bind the modified soft magnetic material powder together to form a uniform and dense coating structure, which can effectively prevent the invasion of corrosive media and protect the substrate from corrosion.

2. The corrosion-resistant magnetic isolation coating material according to claim 1, characterized in that: The polymer is polypyrrole, and the soft magnetic material is nickel ferrite.

3. The corrosion-resistant magnetic isolation coating material according to claim 1, characterized in that: The particle size of the soft magnetic material is 3-5 microns.

4. The corrosion-resistant magnetic isolation coating material according to claim 1, characterized in that: The coating material has no cracking, falling off or rusting after 1000 hours of testing in a salt spray test. For magnets with a surface magnetic strength below 100 Gs, the best magnetic isolation effect can reach more than 70%.

5. The corrosion-resistant magnetic isolation coating material according to claim 1, characterized in that: The soft magnetic material is one or more of nickel ferrite, iron-cobalt alloy or iron-nickel alloy.

6. A method for preparing a corrosion-resistant magnetic isolation coating material, characterized in that: The method for preparing the corrosion-resistant magnetic isolation coating material according to any one of claims 1 to 5 comprises the following specific steps: S1: Disperse the soft magnetic material powder evenly in deionized water, add p-toluenesulfonic acid and pyrrole monomer, and ensure that all components are fully mixed through mechanical stirring and ultrasonic dispersion; S2: preparing an ammonium persulfate solution and slowly adding it dropwise to the mixed solution obtained in step 1, and performing a polymerization reaction for 24 hours by maintaining a mechanical stirring rate of 800 rpm; S3: washing the product with ethanol and removing unreacted substances by centrifugation, followed by drying at 60-80°C until the solid is completely dry; S4: placing the treated brown powder into a high-temperature tube furnace and calcining it at 800-1200 degrees Celsius under nitrogen or argon protection to complete the conversion from polypyrrole to carbon layer; S5: Mix the modified soft magnetic material powder with polyurethane resin, add an appropriate amount of curing agent, and apply it on the magnetic metal substrate through a brush coating process. After natural curing, a corrosion-resistant magnetic isolation coating is formed.

7. The method for preparing the corrosion-resistant magnetic isolation coating material according to claim 6, characterized in that: In step 1, the soft magnetic material is NiFeO4. Every 50g of NiFeO4 powder needs to be dispersed in about 500mL of deionized water, and 15g of p-toluenesulfonic acid and 30-150mL of pyrrole monomer are added.

8. The method for preparing the corrosion-resistant magnetic isolation coating material according to claim 7, characterized in that: In step 2, 100 g of ammonium persulfate was dissolved in 500 mL of deionized water.

9. The corrosion-resistant magnetic isolation coating material and preparation method thereof according to claim 1, characterized in that: In step 4, the calcination temperature is increased at a rate of 5°C / hour and kept at this temperature for 2 hours.

10. The corrosion-resistant magnetic isolation coating material and preparation method thereof according to claim 1, characterized in that: In step 5, the mass ratio of the modified nickel ferrite to the polyurethane resin is preferably 4:1, wherein the modified nickel ferrite is not less than 8 g and the polyurethane resin is not less than 2 g.

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