Preparation method of water-based high-corrosion-resistance coating for neodymium-iron-boron magnet

Abstract

The invention relates to a coating preparation technology, in particular to a preparation method of an aqueous high-corrosion-resistance coating for a neodymium-iron-boron magnet. Comprising the following steps: after vermiculite powder is subjected to intercalation modification treatment in a pillared agent solution, dropwise adding a benzotriazole ionic liquid aqueous dispersion and continuously stirring; a dispersing agent, pigment and filler are subjected to sanding treatment, and nanometer anti-corrosion functional slurry is obtained; then mixing the benzotriazole vermiculite slow-release corrosion-inhibition dispersion liquid, the nano anti-corrosion functional slurry, the modified epoxy resin and the auxiliary agent, stirring and dispersing to obtain a main agent, injecting the main agent into a container, and packaging for later use; the main agent and the independently packaged water-based curing agent form a complete two-component coating system, the water-based curing agent is added into the main agent before use, and the neodymium-iron-boron magnet water-based high-corrosion-resistance coating for application is obtained after stirring and dispersing. Compared with an existing coating process, the treatment process is greatly shortened, the production cost can be reduced, and the anti-corrosion durability of the coating is further enhanced; the anti-corrosion and anti-permeation performance of the coating can be obviously improved.

Description

Technical Field

[0001] This invention relates to coating preparation technology, and in particular to a method for preparing a water-based, highly corrosion-resistant coating for neodymium iron boron magnets. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are widely used in key areas such as robotics and industrial automation, consumer electronics, 5G communication infrastructure, data centers and storage technology, drones and autonomous driving technology, smart homes and the Internet of Things, cloud computing and efficient heat dissipation systems, and high-end medical and precision instruments. However, NdFeB permanent magnets have poor corrosion resistance, while potential applications lie in marine, coastal, and chemical industries where high corrosion resistance is required for equipment and related components. Therefore, it is essential to improve the corrosion resistance of NdFeB permanent magnets.

[0003] Currently, there are two main effective anti-corrosion methods for NdFeB sintered permanent magnets: one is to enhance the corrosion resistance of the magnet itself, and the other is to apply surface protection treatment to the magnet. However, the first method has a significant impact on magnetic properties and increases material costs considerably, and it cannot fundamentally solve the inherent problem of magnet corrosion. Therefore, surface anti-corrosion technology is currently commonly used to reduce the corrosion of permanent magnet materials. This is achieved by covering the magnet surface with a dense coating to isolate oxygen, hydrogen, and water vapor, and by applying a temperature-resistant film to improve the magnet's corrosion resistance in harsh environments.

[0004] Currently, the mainstream surface corrosion protection technologies include:

[0005] (1) Surface phosphating treatment, such as patent document CN 103498139 B. The phosphating process of this type of scheme inevitably results in phosphorus discharge, which will lead to eutrophication of water bodies, algal blooms that hinder the survival of other organisms, and damage the balance of the aquatic ecosystem. It is gradually being replaced. (2) Electrophoresis, such as the published document "Zhang Yuchang et al., Research on Electrophoretic Coating Process of NdFeB Magnets". The coating of this type of scheme has a low anti-corrosion effect. It generally needs to be combined with other processes such as electroplating to achieve better corrosion resistance. (3) Electroplating, such as the scheme disclosed in patent document CN 105803495 B. It is the most widely used process at present. Electroplating can achieve a good anti-corrosion effect. For low anti-corrosion requirements, zinc plating is cheap and simple. For high requirements, multi-layer plating such as nickel and copper is used. However, some chemicals used in the electroplating process contain heavy metals such as chromium, cadmium, and lead. These heavy metals are toxic to the human body. Long-term exposure may lead to damage to the nervous system, liver and kidney problems, etc. (4) Coatings: Currently, oil-based coatings are more commonly used, with high VOC (volatile organic compound) content. They require dilution with strong solvents such as methyl ethyl ketone (MEK) and toluene, which have a significant impact on the ecological environment and human health. Water-based coatings have a smaller impact on the ecological environment and human health, and are the current trend in the industry.

[0006] There have been many reports on the research of waterborne anti-corrosion coatings. For example, Tong Jian et al. (Preparation of nano-slurry and its application in waterborne anti-corrosion coatings, South China University of Technology 2010) utilized the three-dimensional network structure of nano-SiO2 to make it into a slurry and added it to waterborne acrylic anti-corrosion primer and waterborne epoxy anti-corrosion primer to improve the density of the coating and improve the solvent resistance. The highest performance was that the coating remained intact after 208 hours of neutral salt spray test. Li Chongyi et al. (Development of modified glass flake / waterborne epoxy anti-corrosion coating, Electroplating and Finishing 2023, 42 (12)) used silane coupling agent to coat the surface of glass flakes, characterized and analyzed the structure and morphology of the modified product, and then used modified glass flakes as functional fillers to develop epoxy waterborne anti-corrosion coatings. They explored the influence of resin system and modified flakes on coating performance. Since only layered functional fillers were used, the best salt spray performance was that rust spots appeared after 408 hours. The applicant's research team's published literature CN 115011245 B proposes to intercalate amino acids into talc sheet materials and then mix them with acidic silica sol to prepare a composite sol, which solves the problems of poor adhesion, easy cracking, and poor corrosion resistance of inorganic coatings made from acidic silica sol. Finally, a coating with salt spray resistance >2000h was obtained. However, this coating system is an organosilicon system with low surface tension, so it cannot be used for neodymium iron boron magnets that require a surface affinity of ≥30.

[0007] Therefore, this invention proposes a new solution to address the problems of insufficient anti-corrosion capability (duration of resistance to neutral salt spray), insufficient high-pressure accelerated aging (HAST) time, and low surface tension (dyne value) of existing coatings, which is a real need. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a water-based high corrosion-resistant coating for neodymium iron boron magnets.

[0009] To solve the technical problem, the technical solution of the present invention is as follows:

[0010] A method for preparing a water-based, highly corrosion-resistant coating for NdFeB magnets is provided, comprising the following steps:

[0011] (1) Vermiculite powder was added to the pillar agent solution and intercalated under heating, stirring and intermittent ultrasonic conditions to form a stable pillar structure between vermiculite layers; then benzotriazole ionic liquid aqueous dispersion was added dropwise and stirred continuously to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion.

[0012] (2) Dispersant, pigment and filler are added to a nano mill and milled to obtain nano anti-corrosion functional slurry;

[0013] (3) The benzotriazole vermiculite slow-release corrosion-inhibiting dispersion, nano anti-corrosion functional slurry, modified epoxy resin, and additives are mixed, stirred and dispersed, and then used as the main agent. The main agent and separately packaged water-based curing agent form a complete two-component coating system. Before use, water-based curing agent is added to the main agent and stirred and dispersed to obtain a water-based high corrosion-resistant coating for neodymium iron boron magnets.

[0014] As a preferred embodiment of the present invention, in step (1), the intercalation modification treatment conditions are as follows: heating temperature 90°C, stirring speed 800 r / min, ultrasonication for 30 s every 1 min, and continuous treatment for 2 to 5 hours; then, benzotriazole ionic liquid is added dropwise at a stirring speed of 800 r / min for 30 to 60 minutes, and stirring is continued for 10 hours after the addition is completed to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion.

[0015] As a preferred embodiment of the present invention, in step (1), the vermiculite powder has a fineness of 300-500 mesh; in the mixture of vermiculite powder and pillar proppant solution, the solid content of vermiculite powder is 20-40 wt%, and the ratio of pillar proppant to vermiculite powder is 10-15 mmol / g; benzotriazole ionic liquid is added to deionized water and stirred at 1000 r / min to obtain an aqueous dispersion of benzotriazole ionic liquid with a solid content of 30-50%; the mass ratio of benzotriazole ionic liquid to vermiculite powder is controlled to be 1:3-10.

[0016] As a preferred embodiment of the present invention, in step (1), the pillar proppant solution is a keggin ion solution [AlO4Al] that does not contain chloride ions. 12 (OH) 24 (OH2) 12 ] 7+ The benzotriazole ionic liquid is N-alkylbenzotriazole monomethyl carbonate or N-alkylbenzotriazole monomethyl sulfate, wherein the N-alkylbenzotriazole is an ion with a chemical valence of +1, and the alkyl group is one of methyl, n-butyl and n-octyl.

[0017] As a preferred embodiment of the present invention, in step (2), the dispersant is first added to deionized water and stirred at 500 r / min for 5 min; then pigments and fillers are added and stirred at 500 r / min for 20 min to obtain a pre-dispersion liquid; then the pre-dispersion liquid is transferred to a rod-type nano-sand mill and milled for 5 to 10 hours to obtain a nano-anticorrosive functional slurry.

[0018] As a preferred embodiment of the present invention, in step (2), the total solid content of pigments and fillers in the nano-anticorrosion functional slurry is 30-70%, and the mass ratio of dispersant to both is 0.5-5%.

[0019] As a preferred embodiment of the present invention, in step (2), the dispersant is one of BYK190 from BYK Chemical, Evonik Degussa 752W or BASF FA4437; the pigment is one or more of titanium dioxide, iron oxide red, iron blue, medium chrome yellow or carbon black; and the filler is one of mica iron oxide, iron phosphate powder, iron titanium powder or zinc phosphate.

[0020] As a preferred embodiment of the present invention, in step (3), the weight ratio of the modified epoxy resin, nano-anticorrosion functional slurry, benzotriazole vermiculite slow-release corrosion-inhibiting dispersion and the additive is 100-200:100-200:100-200:2-20, and the stirring and dispersion time is 2 hours; the mass ratio of the main agent to the water-based curing agent is 100:20-30, and the stirring and dispersion time of the two is 10 minutes.

[0021] As a preferred embodiment of the present invention, in step (3), the modified epoxy resin is a waterborne acrylic modified epoxy resin synthesized by reacting acrylic acid with waterborne epoxy resin; the additives are leveling agents and wetting agents, wherein the leveling agent is one of BYK333, TEGO410, and BYK381, and the wetting agent is one of TEGO4100, SURFYNOL420, and DOWSIL67; the waterborne curing agent is one or a combination of two of waterborne amino resin or waterborne isocyanate curing agent, wherein the waterborne amino resin is one of Cytec CYMEL385 and CYMEL327, and the waterborne isocyanate curing agent is one of Covestro XP2655 or WD-9100 waterborne isocyanate curing agent.

[0022] The present invention further provides a method for using the water-based high corrosion-resistant coating for NdFeB magnets prepared by the aforementioned method. The coating is applied to the surface of the NdFeB magnet substrate using a reciprocating sprayer and cured under room temperature curing or baking conditions to obtain an anti-corrosion coating. The amount of spraying is controlled so that the thickness of the cured coating is 15-35 μm.

[0023] The room temperature curing refers to standing at room temperature for 24 hours; the baking curing refers to heating from room temperature to 170°C in the oven and holding for 30 minutes, followed by natural cooling.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The conventional use of benzotriazole in this technical field is to add it directly to coating systems to achieve a corrosion inhibitor effect. However, long-term use reports in marine, coastal, and chemical industries, where high corrosion resistance is required for equipment and related parts, have revealed that the long-term effectiveness of this corrosion inhibitor is insufficient to meet the corrosion protection requirements of NdFeB magnets. Therefore, some researchers have proposed using encapsulation, microencapsulation, and other technologies to slow the release of the corrosion inhibitor; however, the preparation techniques for these corrosion inhibitors are complex and costly.

[0026] This invention proposes an innovative method for coating corrosion inhibitors, involving pretreatment by mixing vermiculite powder with a pillar-supporting agent solution, and then using ion exchange to encapsulate Al... 13 Polycations enter the vermiculite interlayer, forming a stable pillared structure. Then, benzotriazole ionic liquid is added, allowing it to adsorb into the vermiculite layers. Based on the stable pillared structure, long-term absorption is achieved, thus replacing the "coating" method in existing technologies. After being added to the coating, the benzotriazole ionic liquid is slowly released from the layers, significantly reducing the consumption rate of the corrosion inhibitor. This invention achieves the adsorption and containment of benzotriazole ionic liquid in vermiculite layers using only a two-step method, greatly reducing the processing steps compared to existing coating processes, lowering production costs, and further enhancing the corrosion resistance and durability of the coating.

[0027] 2. The anti-corrosion filler particles in this invention are at the nanoscale, which can effectively fill micropores and other defects in the coating, block the diffusion path of corrosive media, and significantly improve the anti-corrosion and anti-permeability performance of the coating.

[0028] 3. This invention utilizes the physical form of high-speed shearing, supplemented by chemical modification, to shear micron-scale pigments and fillers to the nanoscale and stably disperse them in the corresponding slurry system. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention.

[0030] Part 1: Overview of the Implementation Schemes of the Invention

[0031] 1. Preparation method of water-based high corrosion-resistant coating for NdFeB magnets

[0032] The water-based high corrosion-resistant coating for neodymium iron boron magnets in this invention is prepared through the following steps:

[0033] (1) Vermiculite powder was added to the pillar agent solution and intercalated under heating, stirring and intermittent ultrasonic conditions to form a stable pillar structure between vermiculite layers; then benzotriazole ionic liquid aqueous dispersion (solution B) was added dropwise and stirred continuously to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion.

[0034] The vermiculite powder has a fineness of 300-500 mesh, and the pillar proppant solution is a keggin ion solution [AlO4Al] which does not contain chloride ions. 12 (OH) 24 (OH2) 12 ] 7+ (This ionic solution is commercially available); in the mixture of vermiculite powder and pillaring agent solution (solution A), the solid content of vermiculite powder is 20-40 wt%, and the ratio of pillaring agent to vermiculite powder is 10-15 mmol / g. The benzotriazole ionic liquid is N-alkylbenzotriazole monomethyl carbonate or N-alkylbenzotriazole monomethyl sulfate, wherein the N-alkylbenzotriazole ion has a +1 valence, and the alkyl group is one of methyl, n-butyl, and n-octyl. The benzotriazole ionic liquid is added to deionized water and stirred at 1000 r / min to obtain an aqueous dispersion of the benzotriazole ionic liquid with a solid content of 30-50%; the mass ratio of benzotriazole ionic liquid to vermiculite powder is controlled at 1:3-10.

[0035] As an example, the intercalation modification treatment conditions are as follows: heating temperature 90℃, stirring speed 800r / min, ultrasonication for 30s every 1min, and continuous treatment for 2 to 5 hours; then, benzotriazole ionic liquid is added dropwise at a stirring speed of 800r / min for 30 to 60 minutes, and stirring is continued for 10 hours after the addition is completed to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion.

[0036] (2) Dispersant, pigment and filler are added to a nano mill and milled to obtain nano anti-corrosion functional slurry;

[0037] The dispersant is one of BYK190 from BYK Chemical, Evonik Degussa 752W, or BASF FA4437; the pigment is one or more of titanium dioxide, iron oxide red, iron blue, medium chrome yellow, or carbon black; and the filler is one of mica iron oxide, ferrophosphorus powder, iron-titanium powder, or zinc phosphate. The total solid content of the pigment and filler in the nano-anticorrosion functional slurry is 30-70%, and the mass ratio of the dispersant to both is 0.5-5%.

[0038] As an example, the dispersant is first added to deionized water and stirred at 500 r / min for 5 min; then pigments and fillers are added and stirred at 500 r / min for 20 min to obtain a pre-dispersion liquid; then the pre-dispersion liquid is transferred to a rod-type nano-sand mill and milled for 5 to 10 hours to obtain a nano-anticorrosive functional slurry.

[0039] (3) The benzotriazole vermiculite slow-release corrosion-inhibiting dispersion, nano anti-corrosion functional slurry, modified epoxy resin, and additives are mixed and stirred to disperse, and then used as the main agent (or base paint), injected into a container and sealed for later use; the main agent and separately packaged water-based curing agent form a complete two-component coating system. Before use, water-based curing agent is added to the main agent, stirred and dispersed to obtain a water-based high corrosion-resistant coating for neodymium iron boron magnets.

[0040] The weight ratio of modified epoxy resin, nano-anticorrosion functional slurry, benzotriazole vermiculite slow-release corrosion-inhibiting dispersion and additives is 100-200:100-200:100-200:2-20, and the stirring and dispersion time is 2 hours; the mass ratio of the main agent to the water-based curing agent is 100:20-30, and the stirring and dispersion time of both is 10 minutes.

[0041] As an example, the modified epoxy resin is a waterborne acrylic modified epoxy resin synthesized by reacting acrylic acid with a waterborne epoxy resin. This resin is commercially available (epoxy value 0.2–0.3, hydroxyl value 80–120 mg KOH / g, viscosity 500–1000 Cp, solid content 40–60%). The additives are leveling agents and wetting agents, wherein the leveling agent is one of BYK333, TEGO410, or BYK381, and the wetting agent is one of TEGO4100, SURFYNOL420, or DOWSIL67. The waterborne curing agent is one or a combination of two of waterborne amino resins or waterborne isocyanate curing agents, wherein the waterborne amino resin is one of Cytec CYMEL385 or CYMEL327, and the waterborne isocyanate curing agent is one of Covestro XP2655 or WD-9100 waterborne isocyanate curing agents.

[0042] 2. Application method of water-based high corrosion-resistant coating for NdFeB magnets

[0043] The coating application method is as follows: the coating is applied to the surface of the neodymium iron boron magnet substrate using a reciprocating sprayer, and then cured under room temperature curing or baking conditions to obtain an anti-corrosion coating. The amount of spraying is controlled so that the thickness of the cured coating is 15-35μm.

[0044] As an example, room temperature curing refers to standing at room temperature for 24 hours; curing under baking conditions refers to heating from room temperature to 170°C in the oven and holding for 30 minutes, followed by natural cooling.

[0045] Part Two: Examples and Comparative Cases

[0046] This invention provides 5 embodiments and 3 comparative examples. The specific operation steps are as described in the overview in Part 1. The operation parameters, related data, and options are detailed in Tables 1 and 2.

[0047] Specifically, Examples 1-5 used an anti-corrosion slurry, a benzotriazole vermiculite slow-release corrosion-inhibiting dispersion, and a modified epoxy resin to prepare a water-based high-corrosion-resistant coating for NdFeB magnets; Comparative Example 1 did not use a nano-anti-corrosion functional slurry; Comparative Example 2 did not use a benzotriazole vermiculite slow-release corrosion-inhibiting dispersion; and in Comparative Example 3, the vermiculite in the slow-release corrosion-inhibiting dispersion was not subjected to pillar-supporting treatment and was simply stirred and mixed with the benzotriazole ionic liquid. Other additions were consistent with the formulation of Example 5 (which had the best overall performance).

[0048] The neutral salt spray resistance test conditions refer to the neutral salt spray (NSS) test method in the national standard GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test; the high pressure aging resistance test refers to the high pressure accelerated aging test method in 7.3.3 of the national standard GB / T 40793-2021 Sintered NdFeB Surface Coating; the surface tension (dyne value) of the coating is tested as follows: Apply the test ink (surface tension test range 28 ~ 72 mN / m) produced by Plasmatreat GmbH, Germany to the coating surface. If the liquid wets the surface (i.e., the liquid spreads continuously on the surface), the surface tension of the tested coating is higher than the nominal surface tension of the test ink. Continue to use a higher grade of test ink to repeat the above process until the liquid no longer wets the surface (i.e., the liquid shrinks on the surface). The surface tension of the last test ink that wets the surface and does not shrink for 2 seconds is the surface tension of the tested coating.

[0049] The coating thicknesses obtained in the five examples and three comparative examples were basically consistent, all ranging from 15 to 16 μm.

[0050] Table 1 Parameter list in the embodiments

[0051]

[0052] Table 2. List of parameters in the comparative example

[0053]

[0054] The following results were obtained from the test data in Tables 1 and 2:

[0055] 1. Comparison of test data between Comparative Example 1 and Example 5: With essentially the same coating thickness, Example 5, by adding an anti-corrosion slurry compared to Comparative Example 1, increased the neutral salt spray resistance from 360h to 760h. This demonstrates that the anti-corrosion slurry significantly improves corrosion resistance in the coating.

[0056] 2. Comparison of test data between Comparative Example 2 and Example 5: With essentially the same coating thickness, Example 5, compared to Comparative Example 2, added benzotriazole vermiculite slow-release corrosion inhibitor dispersion, which increased the high-pressure aging resistance test from 96h to 500h and the neutral salt spray resistance from 240h to 760h. This demonstrates that the benzotriazole vermiculite slow-release corrosion inhibitor dispersion improves the coating's high-pressure aging resistance.

[0057] 3. Comparison of test data between Comparative Example 3 and Example 5: With essentially the same coating thickness, Example 5, compared to Comparative Example 3, uses vermiculite with a pillar-intercalation modified benzotriazole-based slow-release corrosion-inhibiting dispersion. This improved the high-pressure aging resistance test from 168h to 500h and the neutral salt spray resistance from 480h to 760h. This demonstrates that vermiculite and benzotriazole ionic liquid treated with a pillar-intercalation modification process can enhance the PCT resistance and corrosion resistance of the corresponding coatings.

[0058] From this, we can conclude that: (1) Unmodified vermiculite and benzotriazole ionic liquid can improve the coating’s resistance to high pressure aging and neutral salt spray; (2) The benzotriazole vermiculite slow-release corrosion-inhibiting dispersion prepared after pillaring and intercalation modification further improves the coating’s resistance to high pressure aging and neutral salt spray compared to the unmodified one; (3) The main role of the anti-corrosion slurry in this system is to improve the coating’s resistance to neutral salt spray. When combined with the benzotriazole vermiculite slow-release corrosion-inhibiting dispersion, it can significantly improve the coating’s resistance to high pressure aging and neutral salt spray.

[0059] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a water-based, highly corrosion-resistant coating for NdFeB magnets, characterized in that, Includes the following steps: (1) Vermiculite powder was added to the pillar agent solution and intercalated under heating, stirring and intermittent ultrasonic conditions to form a stable pillar structure between vermiculite layers; then benzotriazole ionic liquid aqueous dispersion was added dropwise and stirred continuously to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion. (2) Dispersant, pigment and filler are added to a nano mill and milled to obtain nano anti-corrosion functional slurry; (3) The benzotriazole vermiculite slow-release corrosion-inhibiting dispersion, nano anti-corrosion functional slurry, modified epoxy resin, and additives are mixed, stirred and dispersed, and then used as the main agent. The main agent and separately packaged water-based curing agent form a complete two-component coating system. Before use, water-based curing agent is added to the main agent and stirred and dispersed to obtain a water-based high corrosion-resistant coating for neodymium iron boron magnets.

2. The method according to claim 1, characterized in that, In step (1), the intercalation modification treatment conditions are: heating temperature 90℃, stirring speed 800r / min, ultrasonication for 30s every 1min, and continuous treatment for 2 to 5 hours; then, benzotriazole ionic liquid is added dropwise at a stirring speed of 800r / min for 30 to 60 minutes, and stirring is continued for 10 hours after the addition is completed to obtain benzotriazole vermiculite slow-release corrosion-inhibiting dispersion.

3. The method according to claim 1, characterized in that, In step (1), the vermiculite powder has a fineness of 300-500 mesh; in the mixture of vermiculite powder and pillar proppant solution, the solid content of vermiculite powder is 20-40 wt%, and the ratio of pillar proppant to vermiculite powder is 10-15 mmol / g; benzotriazole ionic liquid is added to deionized water and stirred at 1000 r / min to obtain an aqueous dispersion of benzotriazole ionic liquid with a solid content of 30-50%; the mass ratio of benzotriazole ionic liquid to vermiculite powder is controlled to be 1:3-10.

4. The method according to claim 1, characterized in that, In step (1), the pillar support solution is a keggin ion solution [AlO4Al] that does not contain chloride ions. 12 (OH) 24 (OH2) 12 ] 7+ The benzotriazole ionic liquid is N-alkylbenzotriazole monomethyl carbonate or N-alkylbenzotriazole monomethyl sulfate, wherein the N-alkylbenzotriazole is an ion with a chemical valence of +1, and the alkyl group is one of methyl, n-butyl and n-octyl.

5. The method according to claim 1, characterized in that, In step (2), the dispersant is first added to deionized water and stirred at 500 r / min for 5 min; then pigments and fillers are added and stirred at 500 r / min for 20 min to obtain a pre-dispersion liquid; then the pre-dispersion liquid is transferred to a rod-type nano-sand mill and milled for 5 to 10 hours to obtain a nano-anticorrosive functional slurry.

6. The method according to claim 1, characterized in that, In step (2), the total solid content of pigments and fillers in the nano-anticorrosion functional slurry is 30-70%, and the mass ratio of dispersant to both is 0.5-5%.

7. The method according to claim 1, characterized in that, In step (2), the dispersant is one of BYK190 from BYK Chemical, Evonik Degussa 752W or BASF FA4437; the pigment is one or more of titanium dioxide, iron oxide red, iron blue, medium chrome yellow or carbon black; and the filler is one of mica iron oxide, iron phosphate powder, iron titanium powder or zinc phosphate.

8. The method according to claim 1, characterized in that, In step (3), the weight ratio of the modified epoxy resin, nano-anticorrosion functional slurry, benzotriazole vermiculite slow-release corrosion-inhibiting dispersion and the additive is 100-200:100-200:100-200:2-20, and the stirring and dispersion time is 2 hours; the mass ratio of the main agent to the water-based curing agent is 100:20-30, and the stirring and dispersion time of the two is 10 minutes.

9. The method according to claim 1, characterized in that, In step (3), the modified epoxy resin is a waterborne acrylic modified epoxy resin synthesized by reacting acrylic acid with waterborne epoxy resin; the additives are leveling agents and wetting agents, wherein the leveling agent is one of BYK333, TEGO410, and BYK381, and the wetting agent is one of TEGO4100, SURFYNOL420, and DOWSIL67; the waterborne curing agent is one or a combination of two of waterborne amino resin or waterborne isocyanate curing agent, wherein the waterborne amino resin is one of Cytec CYMEL385 and CYMEL327, and the waterborne isocyanate curing agent is one of Covestro XP2655 or WD-9100 waterborne isocyanate curing agent.

10. A method for using the water-based high corrosion-resistant coating for NdFeB magnets prepared by the method according to any one of claims 1 to 9, characterized in that, The coating is applied to the surface of a neodymium iron boron magnet substrate using a reciprocating sprayer and cured under room temperature curing or baking conditions to obtain an anti-corrosion coating. The amount of spraying is controlled so that the thickness of the cured coating is 15-35μm. The room temperature curing refers to standing at room temperature for 24 hours; the baking curing refers to heating from room temperature to 170°C in the oven and holding for 30 minutes, followed by natural cooling.

Images