阅读说明：本技术 钕铁硼永磁体表面保护液、表面保护膜层及其制备方法 (Neodymium-iron-boron permanent magnet surface protection liquid, surface protection film layer and preparation method thereof ) 是由 白晓刚 于海华 贺元辉 张龙 仉新功 冯志兵 潘广麾 于 2018-06-22 设计创作，主要内容包括：本发明涉及钕铁硼永磁体表面保护液、表面保护膜层及其制备方法。所述钕铁硼永磁体表面保护液中包含15～25重量份的铝元素、0.5～2重量份的镁元素、1.5～3重量份的硅元素、1～5重量份的稀土元素。由本发明的钕铁硼永磁体表面保护液制备的钕铁永磁体表面保护膜层具有卓越的绝缘性、耐腐蚀性、耐磨性、热稳定性,覆盖能力强。(The invention relates to a surface protection liquid for a neodymium iron boron permanent magnet, a surface protection film layer and a preparation method thereof. The surface protection liquid for the neodymium iron boron permanent magnet comprises 15-25 parts by weight of aluminum element, 0.5-2 parts by weight of magnesium element, 1.5-3 parts by weight of silicon element and 1-5 parts by weight of rare earth element. The surface protective film layer of the neodymium-iron permanent magnet prepared by the surface protective liquid of the neodymium-iron-boron permanent magnet has excellent insulativity, corrosion resistance, wear resistance, thermal stability and strong covering capability.)

1. The surface protection liquid for the neodymium-iron-boron permanent magnet is characterized by comprising 15-25 parts by weight of aluminum element, 0.5-2 parts by weight of magnesium element, 1.5-3 parts by weight of silicon element and 1-5 parts by weight of rare earth element.

2. The surface protection solution for the NdFeB permanent magnet as claimed in claim 1, wherein the surface protection solution for the NdFeB permanent magnet contains 0-3 parts by weight of zinc element and/or 0-1.5 parts by weight of iron element.

3. A neodymium iron boron permanent magnet surface protection solution according to claim 2, characterized in that the neodymium iron boron permanent magnet surface protection solution contains 16-20 parts by weight of aluminum element, 1.8-2.5 parts by weight of rare earth element, 1.5-2.5 parts by weight of silicon element, 0-2.8 parts by weight of zinc element, 0-1.5 parts by weight of iron element, and 0.5-1.8 parts by weight of magnesium element.

4. The surface protection film layer for the neodymium-iron-boron permanent magnet is characterized by comprising 15-25 parts by weight of aluminum element, 0.5-2 parts by weight of magnesium element, 1.5-3 parts by weight of silicon element and 1-5 parts by weight of rare earth element.

5. A neodymium iron boron permanent magnet surface protection film layer according to claim 4, characterized in that, the protection film layer contains 0-3 parts by weight of zinc element and/or 0-1.5 parts by weight of iron element.

6. The surface protection film layer of an NdFeB permanent magnet according to claim 5, wherein the protection film layer comprises 16 to 20 parts by weight of aluminum, 1.8 to 2.5 parts by weight of rare earth, 1.5 to 2.5 parts by weight of silicon, 0 to 2.8 parts by weight of zinc, 0 to 1.5 parts by weight of iron and 0.5 to 1.8 parts by weight of magnesium.

7. A method for preparing the surface protection solution for the ndfeb permanent magnet according to any one of claims 1 to 3, wherein the method comprises the following steps:

selecting a mixture of magnesium oxide, aluminum oxide, silicon dioxide and rare earth oxide as a filler, and adding the filler into an aluminum phosphate solution to obtain an intermediate product;

selecting a mixture of silica gel, hydroxymethyl cellulose and a lubricant as a modifier, and adding the modifier into the intermediate product to obtain the surface protection solution for the neodymium-iron-boron permanent magnet;

the aluminum phosphate solution, the filler and the modifier are in the following mass ratio: 1: 0.4-0.7: 0.007 to 0.04.

8. The method for preparing a surface protection solution for neodymium iron boron permanent magnet according to claim 7, wherein the filler further comprises one or a mixture of two of iron oxide and zinc oxide, wherein the mass ratio of magnesium oxide, aluminum oxide, silicon dioxide, rare earth oxide, iron oxide and/or zinc oxide in the filler is as follows: 5-10%: 60-75%: 8-10%: 5-10%: 8-10%; preferably, the rare earth oxide is neodymium oxide and/or cerium oxide; preferably, the particle size of each raw material composing the filler is less than or equal to 100 nm.

9. The method for preparing a surface protection solution for a neodymium iron boron permanent magnet according to claim 7, wherein the lubricant is one or a mixture of zinc stearate, C5 petroleum resin and C9 petroleum resin; preferably, the particle size of each raw material composing the modifier is less than or equal to 100 nm.

10. A preparation method of the surface protection film layer of the NdFeB permanent magnet according to any one of claims 4 to 6, which comprises a pretreatment step, a coating step and a curing step in sequence, wherein the pretreatment step comprises degreasing, derusting and cleaning treatment of the NdFeB permanent magnet,

the coating steps are as follows: taking the surface protection liquid for the NdFeB permanent magnet according to any one of claims 1 to 3, coating the surface protection liquid on the surface of the NdFeB permanent magnet, and then carrying out the curing step to obtain the surface protection film layer of the NdFeB permanent magnet.

Technical Field

The invention relates to the field of material preparation, in particular to a neodymium iron boron permanent magnet surface protection liquid and a preparation method thereof, and a neodymium iron boron permanent magnet surface protection film layer is prepared by utilizing the neodymium iron boron permanent magnet surface protection liquid.

Background

In recent years, the development and application of the neodymium iron boron permanent magnet are very rapid, and meanwhile, the development of the protection technology of the neodymium iron boron permanent magnet is related to whether the material can be popularized in a large range. The Nd-Fe-B permanent magnet is mainly prepared by iron, boron, rare earth metal neodymium and other elements through a powder metallurgy process, and is a magnetic material with the best performance at present. The neodymium iron boron permanent magnet has wide application prospect, and is widely applied to the fields of electroplating devices, machinery, medical treatment, automobiles and the like at present.

The corrosion prevention technology of the neodymium iron boron permanent magnet is a key technology for limiting the application of the neodymium iron boron permanent magnet. As a porous material prepared by a powder metallurgy preparation process, a neodymium-rich phase, a neodymium-iron-boron main phase and a boundary phase in a neodymium-iron-boron permanent magnet are easy to form intergranular corrosion. The rare earth element neodymium in the neodymium-iron-boron powder alloy has more active property, so that the corrosion resistance of the whole neodymium-iron-boron alloy is very poor, and the neodymium-iron-boron powder alloy is very easy to rust and corrode in a damp and hot environment, so that the magnetic property of a permanent magnet is reduced and even lost, the service life of the permanent magnet is seriously influenced, and the stability and the reliability of a product are reduced. In addition, the magnetic performance of the neodymium iron boron permanent magnet has a great relationship with the organization structure of the neodymium iron boron permanent magnet, wherein the main phase of the neodymium iron boron is the main source of the magnetic performance of the neodymium iron boron permanent magnet, and the contribution of the neodymium-rich phase to the coercive force of the permanent magnet is the largest. However, when the ndfeb permanent magnet is corroded, the magnetic performance of the permanent magnet will be greatly changed, and researchers are prompted to pay more and more attention to how to improve the corrosion resistance of the ndfeb permanent magnet.

At present, a better corrosion-resistant effect can be achieved by coating a wear-resistant coating on the surface of the neodymium iron boron permanent magnet. The method for preparing the wear-resistant and corrosion-resistant coating comprises the following steps: thermal spraying, plasma spraying, physical vapor deposition, chemical vapor deposition, sol-gel methods, and the like. Wherein, the cost is too high during physical vapor deposition and chemical vapor deposition; the hot spraying and the plasma spraying are too thick and are not suitable for the corrosion prevention requirement of the neodymium iron boron permanent magnet; the temperature required for the sol-gel process is too high, above the curie temperature of the permanent magnet.

Meanwhile, how to attach a coating with proper thickness, wear resistance, corrosion resistance and strong binding capacity on the surface of the neodymium iron boron permanent magnet is also a key technology for solving the problems in the prior art.

Disclosure of Invention

In view of the above-mentioned problems, the present invention aims to provide a novel surface protection solution for a ndfeb permanent magnet, which can form a protection film on the surface of the ndfeb permanent magnet after being subjected to a proper process treatment, so that the ndfeb permanent magnet has excellent corrosion resistance and wear resistance, thereby effectively prolonging the service life of the ndfeb permanent magnet.

The invention provides a surface protection liquid for a neodymium iron boron permanent magnet, which comprises 15-25 parts by weight of aluminum element, 0.5-2 parts by weight of magnesium element, 1.5-3 parts by weight of silicon element and 1-5 parts by weight of rare earth element.

In a preferred embodiment of the present invention, the surface protection solution for the ndfeb permanent magnet further comprises 0 to 3 parts by weight of a zinc element and/or 0 to 1.5 parts by weight of an iron element.

In a preferred embodiment of the present invention, the surface protection solution for the ndfeb permanent magnet comprises 16 to 20 parts by weight of an aluminum element, 1.8 to 2.5 parts by weight of a rare earth element, 1.5 to 2.5 parts by weight of a silicon element, 0 to 2.8 parts by weight of a zinc element, 0 to 1.5 parts by weight of an iron element, and 0.5 to 1.8 parts by weight of a magnesium element.

The invention also provides a surface protection film layer of the neodymium iron boron permanent magnet, which comprises 15-25 parts by weight of aluminum element, 0.5-2 parts by weight of magnesium element, 1.5-3 parts by weight of silicon element and 1-5 parts by weight of rare earth element.

In a preferred embodiment of the present invention, the protective film further comprises 0 to 3 parts by weight of zinc and/or 0 to 1.5 parts by weight of iron.

In a preferred embodiment of the present invention, the protective film layer comprises 16 to 20 parts by weight of an aluminum element, 1.8 to 2.5 parts by weight of a rare earth element, 1.5 to 2.5 parts by weight of a silicon element, 0 to 2.8 parts by weight of a zinc element, 0 to 1.5 parts by weight of an iron element, and 0.5 to 1.8 parts by weight of a magnesium element.

The invention also provides a preparation method of the surface protection liquid for the neodymium iron boron permanent magnet, which comprises the following steps:

selecting a mixture of magnesium oxide, aluminum oxide, silicon dioxide and rare earth oxide as a filler, and adding the filler into an aluminum phosphate solution to obtain an intermediate product;

selecting a mixture of silica gel, hydroxymethyl cellulose and a lubricant as a modifier, and adding the modifier into the intermediate product to obtain the surface protection solution for the neodymium-iron-boron permanent magnet;

the aluminum phosphate solution, the filler and the modifier are in the following mass ratio: 1: 0.4-0.7: 0.007 to 0.04.

In some embodiments of the present invention, the filler further includes one or a mixture of two of iron oxide and zinc oxide, wherein the mass ratio of magnesium oxide, aluminum oxide, silica, rare earth oxide, iron oxide and/or zinc oxide in the filler is: 5-10%: 60-75%: 8-10%: 5-10%: 8-10%. Preferably, the rare earth oxide is neodymium oxide and/or cerium oxide. More preferably, the particle size of each raw material constituting the filler is 100nm or less.

In some embodiments of the present invention, the lubricant is selected from one or more of zinc stearate, C5 petroleum resin, and C9 petroleum resin. Preferably, the particle size of each raw material composing the modifier is less than or equal to 100 nm.

The invention also provides a preparation method of the surface protective film of the neodymium iron boron permanent magnet, which sequentially comprises a pretreatment step, a coating step and a curing step, wherein the pretreatment step comprises the steps of oil removal, rust removal and cleaning treatment of the neodymium iron boron permanent magnet,

the coating steps are as follows: and (3) taking the surface protection liquid of the neodymium iron boron permanent magnet, coating the surface protection liquid of the neodymium iron boron permanent magnet on the surface of the neodymium iron boron permanent magnet, and then curing to obtain the surface protection film layer of the neodymium iron boron permanent magnet.

The surface protection liquid for the neodymium iron boron permanent magnet prepared by the invention has the advantages of simple preparation process, easy operation and easy control of experimental conditions, and has excellent performance when being used for surface protection of the neodymium iron boron permanent magnet. Specifically, the filler and the modifier are added into the surface protection liquid for the neodymium iron boron permanent magnet, wherein the amount of the added filler is controlled, so that the expansion coefficient of the surface protection film layer of the neodymium iron boron permanent magnet can be effectively reduced, the surface protection film layer of the neodymium iron boron permanent magnet is ensured to have good binding force with a base body, and the surface protection liquid is not easy to crack. Meanwhile, by controlling the addition amount of the modifier, the cracking phenomenon in the film forming process of the surface protection liquid of the neodymium iron boron permanent magnet can be reduced.

The surface protection film layer of the neodymium iron boron permanent magnet prepared by the invention can well improve the corrosion resistance, the wear resistance and the thermal stability of the neodymium iron boron permanent magnet, and has strong covering capability.

Detailed Description

The following detailed description of the embodiments of the present invention will be given in conjunction with examples to better understand the aspects of the present invention and the advantages of its various aspects. However, the specific embodiments and examples described below are for illustrative purposes only and are not intended to limit the present invention.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps that are closely related to the solution according to the present invention are shown, and other details that are not so relevant to the present invention are omitted.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention firstly provides a surface protection liquid for a neodymium-iron-boron permanent magnet, which can form a surface protection film layer of the neodymium-iron-boron permanent magnet after being coated and cured on the surface of the neodymium-iron-boron permanent magnet.

When the surface protection liquid for the neodymium iron boron permanent magnet prepared by the invention forms a protection film layer on the surface of the neodymium iron boron permanent magnet, the thickness of the protection film layer is thin, the amount of the surface protection liquid attached to the neodymium iron boron permanent magnet is small, the accurate measurement of the component proportion of the protection film layer by adopting a chemical analysis method is difficult, and the actual component proportion of the surface protection liquid for the neodymium iron boron permanent magnet does not change in the process of forming the protection film layer by curing.

Based on this, the inventor carries out chemical composition analysis after carrying out curing treatment on a certain amount of the surface protection liquid for the neodymium iron boron permanent magnet, and then can accurately measure the chemical composition of the surface protection liquid for the neodymium iron boron permanent magnet. The condition for controlling the curing process is the same as the curing condition of the surface protection liquid of the neodymium iron boron permanent magnet when forming the protection film layer on the surface of the neodymium iron boron permanent magnet, and further, the component composition of the surface protection liquid of the neodymium iron boron permanent magnet is the component composition of the surface protection film layer of the neodymium iron boron permanent magnet.

The surface protection liquid for the neodymium iron boron permanent magnet comprises, by weight, 15-25 parts of aluminum element, 0.5-2 parts of magnesium element, 1.5-3 parts of silicon element and 1-5 parts of rare earth element. Considering that the surface protection liquid for the neodymium iron boron permanent magnet can reduce the expansion coefficient of the protection film layer when forming the surface protection film layer of the neodymium iron boron permanent magnet, so that the expansion coefficients of the surface protection film layer of the neodymium iron boron permanent magnet and the neodymium iron boron permanent magnet are consistent, the surface protection liquid for the neodymium iron boron permanent magnet provided by the invention also comprises 0-3 parts by weight of zinc element and/or 0-1.5 parts by weight of iron element.

The surface protective film layer of the neodymium iron boron permanent magnet, which is formed by the surface protective liquid of the neodymium iron boron permanent magnet, can obviously improve the corrosion resistance and the wear resistance of the neodymium iron boron permanent magnet and prolong the service life of the neodymium iron boron permanent magnet.

In a preferred embodiment of the present invention, the surface protection solution for a neodymium iron boron permanent magnet provided by the present invention comprises 16 to 20 parts by weight of aluminum element, 1.8 to 2.5 parts by weight of rare earth element, 1.5 to 2.5 parts by weight of silicon element, 0 to 2.8 parts by weight of zinc element, 0 to 1.5 parts by weight of iron element, and 0.5 to 1.8 parts by weight of magnesium element.

In view of cost saving, neodymium and/or cerium are preferred as the rare earth element of the present invention.

Based on the surface protection liquid for the neodymium iron boron permanent magnet, the invention also provides a preparation method of the surface protection liquid for the neodymium iron boron permanent magnet, which comprises the following steps:

1. preparing the raw materials

(1) An aluminum phosphate solution is prepared. The aluminum phosphate solution can be purchased directly.

Meanwhile, the invention also provides a preparation method of the aluminum phosphate solution, which comprises the following steps: firstly, water is added into the aluminum hydroxide and the aluminum hydroxide is uniformly stirred, so that the aluminum hydroxide is fully dispersed in the water, and turbid liquid is obtained because the solubility of the aluminum hydroxide in the water is extremely low. And heating the phosphoric acid solution to 50-60 ℃ while stirring to obtain a warm phosphoric acid solution. Then, the turbid solution is added to a warm phosphoric acid solution under stirring to obtain a mixed solution. And heating the mixed solution until the mixed solution becomes colorless and transparent, thus obtaining the aluminum phosphate solution.

Wherein the amount of the turbid solution added to the phosphoric acid solution is not particularly limited with the object of finally obtaining a colorless and transparent aluminum phosphate solution.

Preferably, the molar ratio of the phosphoric acid solution to the aluminum hydroxide is controlled to be 3.10-3.14: 1. when the molar ratio of the phosphoric acid solution to the aluminum hydroxide is controlled within the range, on one hand, the precipitation reaction between the aluminum hydroxide and the phosphoric acid can be avoided when the concentration of the aluminum hydroxide is too high, and the uniformity of a surface protective film layer of the neodymium iron boron permanent magnet is not facilitated; on the other hand, the corrosion of phosphoric acid solution to the neodymium iron boron permanent magnet matrix caused by too low concentration of aluminum hydroxide is avoided, and the stability of the surface protection film layer of the neodymium iron boron permanent magnet is not facilitated.

In a preferred embodiment of the present invention, the phosphoric acid solution has a mass concentration of 85%.

In this step, the temperature of the heating treatment of the mixed solution is preferably controlled to 90 to 120 ℃. And heating to the required temperature, and then preserving the temperature of the mixed solution for at least 1h to obtain a colorless and transparent aluminum phosphate solution. This is because aluminum phosphate is formed in a very small amount during the dissolution of aluminum hydroxide, and aluminum phosphate can be converted into aluminum dihydrogen phosphate by heating and stirring.

(2) Preparing the filling

The filler of the present invention contains magnesium oxide, aluminum oxide, silicon dioxide, and rare earth oxide. Preferably, the filler of the present invention further comprises one or a mixture of two of iron oxide and zinc oxide. The filler selected by the invention can react with an aluminum phosphate solution to promote the film forming process of the surface protection solution of the neodymium iron boron permanent magnet.

Among them, magnesium oxide can accelerate the curing speed of the film forming process. Alumina and silica are used to form the silicon aluminum film. The addition of rare earth oxide, ferric oxide and zinc oxide can reduce the expansion coefficient of the formed protective film, so that the expansion coefficients of the surface protective film of the neodymium iron boron permanent magnet and the neodymium iron boron permanent magnet are consistent, and the surface protective film of the neodymium iron boron permanent magnet and the matrix have good binding force and are not easy to crack.

In view of cost saving, the rare earth oxide in the present invention is neodymium oxide or cerium oxide, or a mixture of neodymium oxide and cerium oxide.

In the present invention, the mass ratio of each component in the filler is not limited, and as a preferred embodiment, the mass ratio of magnesium oxide, aluminum oxide, silicon dioxide, rare earth oxide, iron oxide and/or zinc oxide in the filler is: 5-10%: 60-75%: 8-10%: 5-10%: 8-10%. Wherein, iron oxide or zinc oxide can be independently selected, and the mass ratio is 8-10%; or a mixture of iron oxide and zinc oxide can be selected, and the mass percentage of the mixture is 8-10%.

(3) Preparation of the modifier

The modifier of the invention is a mixture of silica gel, hydroxymethyl cellulose and a lubricant.

The lubricant is firstly melted in the process of forming the film by the surface protection liquid of the neodymium iron boron permanent magnet, so that the cracking phenomenon in the process of forming the protection film layer can be reduced, the surface of the protection film layer is smoother, and the binding force between the surface protection film layer of the neodymium iron boron permanent magnet and the neodymium iron boron permanent magnet matrix is further enhanced. Based on the above, the lubricant is selected according to the principle that a solid substance which can be melted at about 100-120 ℃ and can not be volatilized below 200 ℃ is selected. In a preferred embodiment of the invention, the lubricant is one or a mixture of zinc stearate, C5 petroleum resin and C9 petroleum resin.

The silica gel also has the function of reducing the cracking phenomenon in the process of forming the surface protective film layer of the neodymium iron boron permanent magnet. The mass of the silica gel accounts for 35-50% of the total mass of the modifier.

The hydroxymethyl cellulose is used for solving the coagulation phenomenon of each raw material in the process of forming the surface protective film layer of the neodymium iron boron permanent magnet, preventing the raw material particles from settling and ensuring the smoothness of the surface protective film layer of the neodymium iron boron permanent magnet.

2. Preparation of surface protection liquid for Nd-Fe-B permanent magnet

And adding the filler into the aluminum phosphate solution, and uniformly mixing to obtain an intermediate product. And then, adding the modifier into the intermediate product, and uniformly mixing to obtain the surface protection liquid for the neodymium iron boron permanent magnet.

In a preferred embodiment of the invention, the mass ratio of the aluminum phosphate solution, the filler and the modifier is controlled as follows: 1: 0.4-0.7: 0.007 to 0.04. More preferably, in the embodiment of the invention, the particle size of each raw material for forming the filler and the modifier is less than or equal to 100nm, which is more favorable for forming a flat and continuous surface protection film layer of the neodymium iron boron permanent magnet.

Wherein the mass ratio of the aluminum phosphate solution to the filler is controlled to be 1: 0.4-0.7, the inventor finds that when the mass ratio of the aluminum phosphate solution to the filler is within the range, the expansion coefficient of the surface protective film layer of the neodymium iron boron permanent magnet can be effectively reduced, and the binding force between the surface protective film layer of the neodymium iron boron permanent magnet and the neodymium iron boron permanent magnet matrix is enhanced.

Controlling the mass ratio of the added modifier to the aluminum phosphate solution to be 0.007-0.04: 1, the inventor finds that when the mass ratio of the modifier to the aluminum phosphate solution is controlled within the range, the cracking phenomenon in the process of forming the surface protective film layer of the neodymium iron boron permanent magnet can be well reduced, and the film forming temperature is obviously reduced and is specifically less than or equal to 300 ℃.

The invention also provides a preparation method of the surface protective film layer of the neodymium iron boron permanent magnet, which sequentially comprises the steps of pretreatment, coating and curing.

(1) The pretreatment steps are as follows: after the neodymium iron boron permanent magnet is subjected to conventional oil and rust removal treatment, the neodymium iron boron permanent magnet is placed into an ultrasonic cleaning device for ultrasonic water washing.

(2) The coating steps are as follows: the surface protection liquid for the neodymium iron boron permanent magnet prepared in the steps of the invention is uniformly coated on the neodymium iron boron permanent magnet. In this step, the process conditions of the coating process are not limited. As a preferred embodiment of the present invention, the coating process of the present invention is selected from a dip coating process or a spray coating process.

Specifically, when a dip coating process is employed: after pretreatment, the neodymium iron boron permanent magnet is taken out from an ultrasonic cleaning device and then placed in the surface protection liquid for the neodymium iron boron permanent magnet prepared by the invention, then the neodymium iron boron permanent magnet is taken out and dried, the dried neodymium iron boron permanent magnet is placed in the surface protection liquid for the neodymium iron boron permanent magnet again, and then the neodymium iron boron permanent magnet is taken out and dried. Until the surface protection liquid of the Nd-Fe-B permanent magnet coated on the surface of the Nd-Fe-B permanent magnet reaches the required thickness.

When the spraying process is adopted: after the neodymium iron boron permanent magnet is pretreated, the neodymium iron boron permanent magnet is taken out from an ultrasonic cleaning device, then the surface protection liquid for the neodymium iron boron permanent magnet prepared by the method is sprayed on the surface of one side of the neodymium iron boron permanent magnet, then the neodymium iron boron permanent magnet is dried, then the surface protection liquid for the other side is sprayed and dried, and the spraying step is repeated for multiple times until the surface protection liquid for the neodymium iron boron permanent magnet with the required thickness is uniformly coated on the surface of the neodymium iron boron permanent magnet. Wherein, the drying temperature is not limited. Preferably, the drying temperature is controlled to be about 80 ℃ in the invention.

(3) The curing step is as follows: the neodymium iron boron permanent magnet after dip coating or spray coating is cured, the process parameters of the curing process are not limited, and the purpose of forming a stable surface protection film layer on the neodymium iron boron permanent magnet is achieved finally.

As a preferred embodiment of the present invention, the specific conditions of the curing process are controlled as follows: the neodymium iron boron permanent magnet coated with the surface protection liquid of the neodymium iron boron permanent magnet is baked for 1-1.5 hours at the temperature of 70-90 ℃, and then baked for 1-1.5 hours at the temperature of 100-120 ℃, so that a uniform and stable surface protection film layer is formed on the surface of the neodymium iron boron permanent magnet.

In a preferred embodiment of the present invention, the thickness of the surface protective film layer of the ndfeb permanent magnet prepared from the surface protective solution is 10 to 30 μm.