Water-based paint for preventing corrosion of neodymium-iron-boron magnet as well as preparation method and application of water-based paint

Abstract

The invention discloses a waterborne coating for corrosion prevention of neodymium-iron-boron magnets and a preparation method and application of the waterborne coating, and the waterborne coating comprises, by weight, 40-70 parts of waterborne dimer acid modified epoxy emulsion; 2-10 parts of a coalescing agent; 0.5-4 parts of a nonionic aqueous dispersant; 2-5 parts of a phenolic aldehyde amine curing agent; 10 to 20 parts of filler; 10-20 parts of a coloring agent and the balance of water. The water-based paint disclosed by the invention can resist high-pressure water vapor erosion and normal-temperature environmental corrosion, the corrosion resistance and adhesive force of the water-based paint are equivalent to those of the existing oil paint, and the water-based paint is free of rusting and bubbling after being tested for 120 hours by PCT. The water-based dimer acid modified epoxy emulsion is used as a main material, and water is used as a diluent in the use process, so that the emission of VOC (volatile organic compounds) in the production process is greatly reduced, the environment friendliness of the production is improved, and in addition, the production cost is relatively low. Meanwhile, by adjusting curing conditions, the hardness, SST, PCT and cohesive strength of the coating can be adjusted, and the requirements of different customers are met.

Description

Technical Field

[0001] The present invention belongs to the field of surface treatment of neodymium iron boron magnets. Specifically, it relates to an aqueous coating for preventing corrosion of neodymium iron boron magnets, its preparation method and application. Background Art

[0002] The market of anti-corrosion paint for magnet surface has long been monopolized by foreign suppliers, and there are almost no domestic producers in China who can provide it. Moreover, the original products are mostly solvent-based products, which do not meet the requirements of energy conservation and emission reduction in China. However, since 2010, the national policy of promoting low VOC emissions has given rise to a great progress in China's waterborne technology. Therefore, we can develop waterborne magnet paint products by using high-performance waterborne epoxy emulsion and amine curing agent. Summary of the Invention

[0003] In order to improve the above technical problems, the present invention provides an aqueous coating. Calculated based on 100 parts by weight, it includes 40 - 70 parts of waterborne dimer acid modified epoxy emulsion; 2 - 10 parts of film-forming auxiliary agent; 0.5 - 4 parts of non-ionic waterborne dispersant; 2 - 5 parts of phenolic amine curing agent; 10 - 20 parts of filler; 10 - 20 parts of colorant and the balance of water.

[0004] According to an embodiment of the present invention, the solid content of the aqueous coating is 35 - 55 wt%.

[0005] According to an embodiment of the present invention, the solid content of the waterborne dimer acid modified epoxy emulsion is 40 - 55 wt%.

[0006] According to an embodiment of the present invention, in the aqueous coating, the waterborne dimer acid modified epoxy emulsion is 45 - 70 parts, such as 40 parts, 46 parts, 48 parts, 50 parts, 52 parts, 54 parts, 60 parts, 62 parts or 65 parts.

[0007] According to an embodiment of the present invention, the film-forming auxiliary agent is selected from one or more of ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, dipropylene glycol butyl ether (DPNB) and propylene glycol phenyl ether, such as Greesol TMA04PG - 50 (Yueyang Kaimen Auxiliary Agent Company), ECOSURF TM EH - 9 Surfactan (Dow Chemical), TO - 10 (BASF).

[0008] According to an embodiment of the present invention, in the aqueous coating, the film-forming auxiliary agent is 3 - 6 parts, such as 3 parts, 4 parts, 5 parts or 6 parts.

[0009] According to an embodiment of the present invention, the non-ionic aqueous dispersant is selected from at least one of carboxylic acid compounds. For example, it is a carboxylate salt, and more specifically, at least one of an alkali metal salt of a carboxylic acid, an alkaline earth metal salt of a carboxylic acid, or an alkali metal-alkaline earth metal salt of a carboxylic acid, such as sodium carboxylate, sodium magnesium carboxylate, etc.

[0010] According to an embodiment of the present invention, in the aqueous coating, the amount of the non-ionic aqueous dispersant is 1 part, 2 parts, 3 parts, or 4 parts.

[0011] According to an embodiment of the present invention, the phenolic amine curing agent is selected from one of a water-soluble type or an emulsion type.

[0012] According to an embodiment of the present invention, in the aqueous coating, the amount of the phenolic amine curing agent is 2 parts, 3 parts, 4 parts, or 5 parts.

[0013] According to an embodiment of the present invention, the filler is selected from one or more of pearlescent powder, mica powder, talc powder, and feldspar powder.

[0014] According to an embodiment of the present invention, in the aqueous coating, the amount of the filler is 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts.

[0015] According to an embodiment of the present invention, the aqueous coating further includes 10 - 20 parts of a colorant, such as 10 parts, 12 parts, 14 parts, 15 parts, 16 parts, 18 parts, or 20 parts.

[0016] The present invention also provides a method for preparing the above aqueous coating, which includes:

[0017] (1) Mix an aqueous dimer acid-modified epoxy emulsion, a non-ionic aqueous dispersant, a film-forming aid, a filler, a colorant, and water to obtain a main agent solution with a pH of 8 or higher;

[0018] (2) Mix a phenolic amine curing agent and water to obtain a curing agent solution with a pH of 8 or higher;

[0019] (3) Mix the main agent solution and the curing agent solution to obtain the aqueous coating.

[0020] According to an embodiment of the present invention, step (1) is: Mix an aqueous dimer acid-modified epoxy emulsion, a non-ionic aqueous dispersant, and water, then add a filler for dispersion to obtain a mixture, and add a film-forming aid and a colorant to the mixture for mixing to obtain a main agent solution with a pH of 8 or higher.

[0021] According to an embodiment of the present invention, in step (2), the equivalent ratio of the active hydrogen of the aqueous dimer acid-modified epoxy emulsion to the epoxy component of the main agent is 0.7 - 0.9.

[0022] The present invention also provides the use of the above aqueous coating for the anti-corrosion of NdFeB magnets.

[0023] The present invention also provides an NdFeB magnet with an anti-corrosion coating, which comprises an NdFeB magnet substrate and an anti-corrosion coating on the surface of the NdFeB magnet, and the anti-corrosion coating contains the above aqueous coating.

[0024] According to an embodiment of the present invention, at least one side of the NdFeB magnet substrate contains the anti-corrosion coating.

[0025] According to an embodiment of the present invention, the NdFeB magnet substrate can be an NdFeB magnet well-known in the art.

[0026] According to an embodiment of the present invention, the thickness of the anti-corrosion coating is 15 - 20 microns.

[0027] In the present invention, the composition and structure of the NdFeB magnet substrate are not particularly limited, and a conventional NdFeB magnet in the art can be used.

[0028] The present invention also provides a preparation method of an NdFeB magnet with an anti-corrosion coating, and the method includes:

[0029] (S1) Coating an aqueous coating on at least one side of the NdFeB magnet substrate;

[0030] (S2) Curing the product obtained in step (S1) to obtain the NdFeB magnet with the anti-corrosion coating.

[0031] According to an embodiment of the present invention, in step (S1), the aqueous coating can also be pretreated before coating, and the pretreatment is: stirring the aqueous coating with a dispersion stirring paddle for more than 30 minutes to ensure that the coating is evenly stirred, adding 20 - 30% deionized water while stirring, and then stirring for more than 30 minutes to obtain a pretreated aqueous coating.

[0032] According to an embodiment of the present invention, in step (S1), the viscosity of the pretreated aqueous coating is 10 - 18 s, preferably 12 - 15 s.

[0033] According to an embodiment of the present invention, in step (S1), the viscosity test method of the aqueous coating and the pretreated aqueous coating is the 4 - cup coating test method.

[0034] According to an embodiment of the present invention, in step (S1), the aqueous coating can be coated on one side of the NdFeB magnet substrate, or can be coated on all surfaces of the NdFeB magnet substrate.

[0035] According to an embodiment of the present invention, in step (S1), the coating can be carried out by spraying, for example, by using an automatic spraying device for coating.

[0036] Exemplarily, the nozzle diameter of the spraying device is The spray gun pressure is 0.2 - 0.5 MPa.

[0037] According to the embodiment of the present invention, in step (S2), the curing temperature is 160 - 200 °C and the time is 10 - 30 min. By adjusting the curing temperature and time, the present invention can control the crosslinking degree of the waterborne coating and achieve the adjustment of the coating hardness, SST, PCT and the cohesive strength of the coating.

[0038] According to the embodiment of the present invention, before curing in step (S2), it further includes a step of flash drying at room temperature for 20 - 60 min.

[0039] According to the embodiment of the present invention, the method further includes a pretreatment step (S0):

[0040] The neodymium iron boron magnet substrate is successively polished to remove rust, degreased, treated with water-based and passivated. After the pretreatment is completed, coating is carried out.

[0041] Preferably, a polishing material is used for polishing to remove rust; exemplarily, the polishing material may be at least one of corn cob, wood chip particles and resin abrasive.

[0042] More preferably, before successively polishing the neodymium iron boron magnet substrate to remove rust, it can also be dry-ground to chamfer the R angle with an abrasive first.

[0043] Exemplarily, the abrasive is selected from one or both of silicon carbide and emery. Among them, the silicon carbide accounts for 20 - 50 wt% of the total abrasive amount.

[0044] Exemplarily, the silicon carbide can be one or more of spherical, oblique triangular and oblique cylindrical, and the particle size of the silicon carbide is The particle size of the emery is

[0045] As an exemplary embodiment of the present invention, the method for preparing the neodymium iron boron magnet containing an anti-corrosion coating specifically includes:

[0046] 1) Processing the sintered neodymium iron boron blank and chamfering the C angle as required;

[0047] 2) Chamfering: Using silicon carbide and emery abrasives, dry-grinding to chamfer the R angle in a certain proportion, and the product after chamfering the R angle is polished and rust-proofed with a polishing material;

[0048] 3) Cleaning: The neodymium iron boron product after polishing and rust-proofing is degreased, treated with water-based and passivated;

[0049] 4) Spraying: Spraying a waterborne coating on the neodymium iron boron with an automatic spraying device;

[0050] 5) Curing: After spraying, surface drying and curing of the product are carried out to obtain the NdFeB magnet with the anti-corrosion coating.

[0051] Advantages of the present invention:

[0052] (1) The waterborne coating of the present invention can resist high-pressure steam erosion and environmental corrosion at room temperature. Not only its corrosion resistance and adhesion are comparable to those of existing oil-based coatings, and it can achieve no rusting and blistering in the PCT test for 120 hours. Moreover, since it uses waterborne dimer acid modified epoxy emulsion as the main material and water as the diluent during use, the emission of VOC in the production process is greatly reduced, the production environmental protection is improved, and in addition, it has a lower production cost. At the same time, by adjusting the curing conditions, the adjustment of the coating hardness, SST, PCT and the cohesive strength of the coating can be realized to meet the requirements of different customers.

[0053] (2) For the anti-corrosion coating of the NdFeB magnet containing the anti-corrosion coating of the present invention, as the curing temperature increases or the curing time prolongs, the crosslinking degree of the coating gradually increases during the film-forming process, the hardness will gradually increase from 2H to 4H, and the PCT performance is also improved. Specific embodiments

[0054] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection of the present invention.

[0055] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0056] Testing methods:

[0057] Thermal shock: The sintered NdFeB magnet with the anti-corrosion coating is subjected to a cyclic test from -40°C to 150°C in a thermal shock test chamber, and is maintained at a constant temperature for 0.5 h at each temperature (-40°C and 150°C), and a total of 300 cycles of cyclic tests are carried out.

[0058] ATF durability: The sintered NdFeB magnet with the anti-corrosion coating is immersed in ATF oil containing 0.5% water and maintained at 150°C for 1500 h.

[0059] Cross-cut adhesion: GB / T 9286-2021.

[0060] The formulations of the waterborne coatings in Examples 1-7 are as follows:

[0061] Example 1

[0062] 15 parts of distilled water, 40 parts of waterborne dimer acid modified epoxy emulsion (STW612 with a solid content of 55 wt%), 2 parts of DPNB film-forming aid, 4 parts of non-ionic waterborne dispersant sodium carboxylate, 4 parts of phenolic amine-based waterborne curing agent (Bayer waterborne curing agent 2451), 18 parts of 800-mesh talc powder, 17 parts of coloring pigment.

[0063] Example 2

[0064] 10 parts of distilled water, 50 parts of waterborne dimer acid modified epoxy emulsion (Intergre 1030 with a solid content of 52 wt%), 3 parts of DPNB film-forming aid, 3 parts of non-ionic waterborne dispersant sodium carboxylate, 3 parts of phenolic amine-based waterborne curing agent, 15 parts of 800-mesh talc powder, 16 parts of coloring pigment.

[0065] Example 3

[0066] 12 parts of distilled water, 60 parts of waterborne dimer acid modified epoxy emulsion (STW612 with a solid content of 55 wt%), 4 parts of GreesolTM A04PG-50 (Yueyang Kaimen Additives Co., Ltd.) film-forming aid, 1 part of non-ionic waterborne dispersant sodium carboxylate, 3 parts of phenolic amine-based waterborne curing agent (SM2125 of Jiangsu Sanmu Chemical Co., Ltd.), 10 parts of 800-mesh talc powder, 10 parts of coloring pigment.

[0067] Example 4

[0068] 10 parts of distilled water, 62 parts of waterborne dimer acid modified epoxy emulsion (Intergre 1030 with a solid content of 52 wt%), 3 parts of Greesol TM A04PG-50 (Yueyang Kaimen Additives Co., Ltd.) film-forming aid, 1 part of non-ionic waterborne dispersant sodium carboxylate, 3 parts of phenolic amine-based waterborne curing agent (SM2125 of Jiangsu Sanmu Chemical Co., Ltd.), 11 parts of 800-mesh talc powder, 10 parts of coloring pigment.

[0069] Example 5

[0070] 20 parts of distilled water, 62 parts of waterborne dimer acid modified epoxy emulsion (STW612 with a solid content of 55 wt%), ECOSURF TM 3 parts of EH-9 Surfactan (Dow Chemical) film-forming aid, 1 part of non-ionic waterborne dispersant sodium carboxylate, 3 parts of phenolic amine-based waterborne curing agent (2217 of Hubei Baiwei Epoxy New Materials Co., Ltd.), 13 parts of 800-mesh talc powder, 15 parts of coloring pigment.

[0071] Example 6

[0072] 5 parts of distilled water, 65 parts of waterborne dimer acid modified epoxy emulsion (Intergre 1030 with a solid content of 52 wt%), ECOSURF TM2 parts of EH-9 Surfactan (Dow Chemical) film-forming aid, 1 part of non-ionic water-based dispersant sodium carboxylate, 2 parts of phenolic amine water-based curing agent (2217 from Hubei Baiwei Epoxy New Materials Co., Ltd.), 11 parts of 800 mesh talc, and 14 parts of coloring pigments.

[0073] Example 7

[0074] 15 parts of distilled water, 52 parts of water-based dimer acid modified epoxy emulsion (STW612 with a solid content of 52wt%), 3 parts of TO-10 (BASF) film-forming aid, 1 part of non-ionic water-based dispersant sodium carboxylate, 3 parts of phenolic amine water-based curing agent (2218 of Hubei Baiwei Epoxy New Materials Co., Ltd.), 12 parts of 800 mesh talc, and 14 parts of coloring pigments.

[0075] Comparative Example 1

[0076] 15 parts of distilled water, 40 parts of water-based dimer acid modified epoxy emulsion (STW612 with a solid content of 30%), 2 parts of TO-10 (BASF) film-forming aid, 4 parts of non-ionic water-based dispersant sodium carboxylate, 4 parts of phenolic amine water-based curing agent (2218 of Hubei Baiwei Epoxy New Materials Co., Ltd.), 18 parts of 800 mesh talc, and 17 parts of coloring pigments.

[0077] Comparative Example 2

[0078] 15 parts of distilled water, 40 parts of water-based dimer acid modified epoxy emulsion (STW612 with a solid content of 60%), 2 parts of TO-10 (BASF) film-forming aid, 4 parts of non-ionic water-based dispersant sodium carboxylate, 4 parts of phenolic amine water-based curing agent (2218 of Hubei Baiwei Epoxy New Materials Co., Ltd.), 18 parts of 800 mesh talc, and 17 parts of coloring pigments.

[0079] Comparative Example 3

[0080] 35 parts of distilled water, 35 parts of water-based dimer acid modified epoxy emulsion (1030 with a solid content of 52wt% from Intergrey), 3 parts of TO-10 (BASF) film-forming aid, 2 parts of non-ionic water-based dispersant sodium carboxylate, 3 parts of phenolic amine water-based curing agent (2218 from Hubei Baiwei Epoxy New Materials Co., Ltd.), 10 parts of 800 mesh talc, and 12 parts of coloring pigments.

[0081] Comparative Example 4

[0082] 7 parts of distilled water, 75 parts of water-based dimer acid modified epoxy emulsion (1030 with a solid content of 52wt% from Intergrey), 2 parts of TO-10 (BASF) film-forming aid, 2 parts of non-ionic water-based dispersant sodium carboxylate, 3 parts of phenolic amine water-based curing agent (2218 from Hubei Baiwei Epoxy New Materials Co., Ltd.), 6 parts of 800 mesh talc, and 5 parts of coloring pigments.

[0083] The preparation methods of the waterborne coatings of Examples 1-7 and Comparative Examples 1-4 are as follows:

[0084] (1) Mix the waterborne dimer acid-modified epoxy emulsion, non-ionic waterborne dispersant, film-forming aid, filler, colorant and water to obtain a main agent solution with a pH above 8;

[0085] (2) Mix the phenolic amine curing agent and water to obtain a curing agent solution with a pH above 8;

[0086] (3) Mix the main agent solution and the curing agent solution to obtain the waterborne coating.

[0087] Perform performance tests on the waterborne coatings of Examples 1-7 and Comparative Examples 1-4, and the test results are shown in Table 1 below.

[0088] Table 1

[0089] Viscosity Fineness Solid content (%) VOC content (g / L) Inspection standard GB / T1723 (T4 cup) GB / T1724 GB / T1725 GB / 37884 Example 1 38 41 49.5 50 Example 2 39 41 50.4 59 Example 3 36 42 47.2 68 Example 4 36 44 48.9 69 Example 5 36 45 47.5 52 Example 6 39 45 51.3 70 Example 7 37 42 48.4 59 Comparative example 1 33 41 45.3 46 Comparative example 2 47 41 54.2 56 Comparative example 3 35 41 54.7 43 Comparative example 4 35 41 38.9 75

[0090] Application Example 1

[0091] (1) Successively polish, remove rust, degrease, perform water treatment and passivation on the NdFeB magnet substrate to obtain the pretreated NdFeB magnet substrate.

[0092] (2) Stir the waterborne coatings of Examples 1-7 and Comparative Examples 1-4 with a dispersion stirring paddle for 30 min to make the coatings evenly stirred. While stirring, add 25% deionized water, and then stir for another 30 min to obtain the pretreated waterborne coatings. The viscosities of the pretreated waterborne coatings are 12 s, 14 s, 13 s, 12 s, 12 s, 14 s, 15 s, 12 s, 16 s, 16 s, 14 s respectively.

[0093] (3) Use an automatic spraying device to coat the pretreated waterborne coating in step (2) on the surface of the NdFeB substrate in step (1) with a thickness of 20 μm to obtain the sprayed sintered NdFeB magnet.

[0094] (4) Flash dry the sprayed sintered NdFeB magnet at room temperature for 20 minutes and cure it at 160 °C for 20 min to obtain the sintered NdFeB magnets A11-A17 (corresponding to Examples 1-7 in sequence), B11-B14 (corresponding to Comparative Examples 1-4 in sequence) containing the anti-corrosion coating.

[0095] Application Example 2

[0096] Steps (1)-(3) are the same as those in Application Example 1, and the difference lies in: in step (4):

[0097] The sintered NdFeB magnets after spraying are flash-dried at room temperature for 30 minutes and cured at 200 °C for 30 min to obtain sintered NdFeB magnets A21 - A27 (corresponding to Examples 1 - 7 in sequence), B21 - B24 (corresponding to Comparative Examples 1 - 4 in sequence) with anti-corrosion coatings.

[0098] The NdFeB magnets A11 - A17, B11 - B14, A21 - A27, B21 - B24 with anti-corrosion coatings in the application examples are tested for corrosion resistance, and the test results are as described in Table 2 below:

[0099] Table 2 Performance Test of Products A11 - A17, B11 - B14, A21 - A27, B21 - B24

[0100]

[0101]

[0102] The appearances of the products A11 - A17, B11 - B14, A21 - A27, B21 - B24 in the application examples are all smooth and flat, capable of meeting the requirements of no abnormality in thermal shock and ATF durability, and the cross-cut adhesion can also achieve grade 0 without peeling.

[0103] By comparing Product A11 with B11 and B12 in the product application examples, for B11 and B12 where the solid content of the waterborne dimer acid modified epoxy emulsion is not within the range of 40 - 60 wt%, the SST and PCT of the waterborne coating are significantly reduced, and the corrosion resistance becomes worse. For B13, B14 and B23, B24, whether the waterborne dimer acid modified epoxy emulsion is too high or too low, it will also cause a significant reduction in the PCT of the waterborne coating.

[0104] By comparing Product A11 - A17 with A21 - A27 in the product application examples, it can be found that as the curing temperature increases or the curing time prolongs, the crosslinking degree of the coating gradually increases during the film-forming process, the hardness gradually increases from 2H to 4H, and the comprehensive performance of the SST and PCT of the product is also improved.

[0105] As described above, the embodiments of the present invention have been exemplarily described. However, the protection scope of the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An aqueous coating, characterized in that based on 100 parts by weight, it comprises 40 - 70 parts of an aqueous dimer acid - modified epoxy emulsion; 5 - 25 parts of water; 2 - 10 parts of a film - forming aid; 0.5 - 4 parts of a non - ionic aqueous dispersant; 2 - 5 parts of a phenolic amine - type curing agent; 10 - 20 parts of a filler; 10 - 20 parts of a colorant and the balance of water.

2. The aqueous coating according to claim 1, characterized in that the solid content of the aqueous coating is 35 - 55 wt%. Preferably, the solid content of the aqueous dimer acid - modified epoxy emulsion is 40 - 55 wt%.

3. The aqueous coating according to claim 1 or 2, characterized in that in the aqueous coating, the amount of the aqueous dimer acid - modified epoxy emulsion is 45 - 60 parts. Preferably, the film - forming aid is selected from one or more of ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether and propylene glycol phenyl ether. Preferably, the non - ionic aqueous dispersant is selected from at least one of carboxylic acid compounds, such as sodium carboxylate or magnesium carboxylate.

4. The preparation method of the aqueous coating according to any one of claims 1 - 3, characterized in that the method comprises: (1) Mixing the aqueous dimer acid - modified epoxy emulsion, the non - ionic aqueous dispersant, the film - forming aid, the filler, the colorant and water to obtain a main agent solvent with a pH above 8; (2) Mixing the phenolic amine - type curing agent and water to obtain a curing agent solvent with a pH above 8; (3) Mixing the main agent solvent and the curing agent solvent to obtain the aqueous coating.

5. The aqueous coating according to any one of claims 1 - 3 is used for the anti - corrosion of neodymium - iron - boron magnets.

6. A neodymium - iron - boron magnet with an anti - corrosion coating, characterized in that it comprises a neodymium - iron - boron magnet substrate and an anti - corrosion coating on the surface of the neodymium - iron - boron magnet, and the anti - corrosion coating contains the aqueous coating according to any one of claims 1 - 3.

7. The neodymium - iron - boron magnet with an anti - corrosion coating according to claim 6, characterized in that at least one side of the neodymium - iron - boron magnet substrate contains the anti - corrosion coating.

8. The neodymium - iron - boron magnet with an anti - corrosion coating according to claim 6, characterized in that the thickness of the anti - corrosion coating is 15 - 20 microns.

9. The preparation method of the neodymium - iron - boron magnet with an anti - corrosion coating according to any one of claims 6 - 8, characterized in that the method comprises: (S1) Coating at least one side of the neodymium - iron - boron magnet substrate with the aqueous coating according to any one of claims 1 - 3; (S2) Curing the product obtained in step (S1) to obtain the neodymium - iron - boron magnet with an anti - corrosion coating.

10. According to the preparation method of claim 9, characterized in that in step (S1), the aqueous coating can also be pretreated before coating, and the pretreatment is: stirring the aqueous coating with a dispersion stirrer for more than 30 min to ensure uniform stirring of the coating, adding 20 - 30% of deionized water while stirring, and then stirring for more than 30 min to obtain a pretreated aqueous coating; Preferably, the viscosity of the pretreated aqueous coating is 10 - 18 s, preferably 12 - 15 s.

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