A method for surface treatment of a neodymium-iron-boron magnet and a neodymium-iron-boron magnet

Abstract

The present invention provides a surface treatment method for a neodymium iron boron magnet and a neodymium iron boron magnet, belonging to the technical field of preparation of rare earth permanent magnet materials. The surface treatment method includes: preparing a magnet to be electroplated with a clean and rough surface; connecting it to a power supply and immersing it in a plating solution, and forming a corrosion-resistant coating on the surface of the magnet to be electroplated by the ion exchange electrodeposition method; wherein, the ion exchange electrodeposition method includes a first stage of synchronously applying a constant magnetic field and a variable-frequency electric field and a second stage of synchronously applying a rotating magnetic field and a variable-frequency electric field. The intensities of the constant magnetic field and the rotating magnetic field are 1000 gs to 3000 gs, and the rotation speed of the rotating magnetic field is 20 rpm / min to 100 rpm / min. The present invention provides a surface treatment method for a neodymium iron boron magnet, which adopts the synergistic strengthening of the variable-frequency electric field and the magnetic field for the ion exchange deposition technology to improve the deposition efficiency and corrosion resistance of the coating, and efficiently prepares a neodymium iron boron magnet with excellent corrosion resistance effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of rare earth permanent magnet materials, and particularly relates to a surface treatment method for NdFeB magnets and NdFeB magnets. Background Art

[0002] NdFeB permanent magnet materials have the characteristics of high remanence, high magnetic energy product, and high intrinsic coercivity, and are the strongest in magnetic properties among permanent magnet materials. Rare earth permanent magnet materials are widely used in new energy vehicles, maglev trains, wind power generation, energy-saving household appliances and other fields. At present, the requirements for the performance and stability of rare earth permanent magnet materials are getting higher and higher. Due to the special composition and structure of NdFeB permanent magnet materials, their corrosion resistance is not good. Therefore, the research on the corrosion resistance of NdFeB permanent magnet materials is one of the keys to solving the performance, stability and safety of NdFeB permanent magnet materials.

[0003] Currently, in industrial applications, the surface treatment of NdFeB magnetic materials usually uses electroplating technology. Generally, electroplating technology only uses the current density as a control factor, but is often restricted by the diffusion rate of ions in the solution, which in turn affects the deposition efficiency. An external magnetic field helps to improve the ion diffusion rate and thus improve the deposition efficiency, but the magnetoelectric effect generated by the continuous magnetic field will affect the uniformity of the coating. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a surface treatment method for NdFeB magnets and NdFeB magnets, aiming to solve at least one of the technical problems in the background art.

[0005] The present invention is implemented as follows:

[0006] The first aspect of the present invention provides a surface treatment method for NdFeB magnets, and the method includes the following steps:

[0007] Pretreatment of NdFeB magnets to obtain a magnet to be electroplated with a clean and rough surface;

[0008] Connect the magnet to be electroplated to a power supply and immerse it in a plating solution, and form a corrosion-resistant coating on the surface of the magnet to be electroplated by ion exchange electroplating;

[0009] Wherein, the ion exchange electroplating method includes two stages. In the first stage, a constant magnetic field and a variable-frequency electric field are applied synchronously; in the second stage, a rotating magnetic field and a variable-frequency electric field are applied synchronously. The intensity of the constant magnetic field and the rotating magnetic field is 1000 gs to 3000 gs, and the rotation speed of the rotating magnetic field is 20 rpm / min to 100 rpm / min.

[0010] Further, the conditions of the variable-frequency electric field include: the current density of the positive pulse is 8 A / dm 2, the working frequency is 400 Hz to 800 Hz, and the duty cycle is 20% to 60%; the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, and the duty cycle is 20%.

[0011] Furthermore, the processing time of the first stage is 10 min to 15 min; the processing time of the second stage is 10 min to 15 min.

[0012] Furthermore, the processing temperature of the ion exchange electrodeposition method is 45°C ± 5°C.

[0013] Furthermore, the pretreatment of the neodymium iron boron magnet specifically includes:

[0014] First, place the neodymium iron boron magnet in an alkaline cleaning solution at 65°C ± 5°C, stir to remove the oil stain on the neodymium iron boron magnet, and wash it clean with water;

[0015] Then, immerse the neodymium iron boron magnet in the HNO 3 solution for 30 s ± 5 s, and then wash it clean with water;

[0016] Next, immerse the neodymium iron boron magnet in the H 2 SO 4 solution for 30 s ± 5 s, wash it clean with water, and then ultrasonically clean it with absolute ethanol to obtain a magnet to be electroplated with a clean and rough surface.

[0017] Furthermore, the alkaline cleaning solution includes NaOH, Na 2 CO 3 , Na 3 PO 4 , emulsifier and sodium dodecyl sulfate.

[0018] The second aspect of the present invention provides a neodymium iron boron magnet obtained by surface treatment through the above method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention provides a surface treatment method for neodymium iron boron magnets, which uses a variable-frequency electric field and magnetic field to synergistically strengthen the ion exchange deposition technology to improve the deposition efficiency and corrosion resistance of the coating, and efficiently produces a neodymium iron boron magnet with excellent corrosion resistance.

[0021] 2. The present invention uses the strengthened ion exchange deposition technology to apply a magnetic field and an electric field to the magnet to be plated in two stages. By applying a constant magnetic field and an electric field in the first stage, the coating quality and deposition efficiency are improved. By applying a rotating magnetic field and a variable-frequency electric field in the second stage, the coating flatness is improved. Specific Embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] A surface treatment method for neodymium iron boron magnets, the method comprising steps 1 to 4:

[0024] Step 1, alkaline cleaning pretreatment of neodymium iron boron magnets;

[0025] The neodymium iron boron magnets in the present invention are sintered neodymium iron boron magnets, including but not limited to sintered neodymium iron boron magnets of grades N40, N45, N45H, and N38SH;

[0026] First, place the neodymium iron boron magnet in an alkaline cleaning solution at 65°C ± 5°C, stir to remove the oil stain on the neodymium iron boron magnet, and wash it clean with water; the alkaline cleaning solution includes NaOH, Na 2 CO 3 、Na 3 PO 4 、emulsifier and sodium dodecyl sulfate, not limited to the listed alkaline cleaning solution formula; the alkaline cleaning solution can also be other liquids allowed in the art;

[0027] Step 2, acid pickling pretreatment of neodymium iron boron magnets to obtain a magnet to be electroplated with a clean and rough surface;

[0028] (1) Immerse the neodymium iron boron magnet in a 6wt% HNO 3 solution for 30s ± 5s, and then wash it clean with water;

[0029] (2) Immerse the neodymium iron boron magnet in a 3wt% H 2 SO 4 solution for 30s ± 5s, wash it clean with water and then ultrasonically clean it with absolute ethanol to obtain a magnet to be electroplated with a clean and rough surface.

[0030] Step 3, connect the magnet to be electroplated to a power supply and immerse it in a plating solution, and form a corrosion-resistant coating on the surface of the magnet to be electroplated by ion exchange electrodeposition;

[0031] Among them, the ion exchange electrodeposition method includes two stages. In the first stage, a constant magnetic field with a magnetic field intensity of 1000gs to 3000gs and a variable frequency electric field are applied synchronously, and the treatment time is 10 min to 15 min; in the second stage, a rotating magnetic field (magnetic field intensity of 1000gs to 3000gs, rotation speed of 20 rpm / min to 100 rpm / min) and a variable frequency electric field are applied, and the treatment time is 10 min to 15 min; the treatment temperature of the ion exchange electrodeposition method is 45°C ± 5°C.

[0032] In specific implementation, the conditions of the variable-frequency electric field include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 400 Hz to 800 Hz, and the duty cycle is 20% to 60%; the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, and the duty cycle is 20%.

[0033] The plating solution in this step 3 can adopt any plating solution that can form a corrosion-resistant coating allowed in the art, including but not limited to nickel-based electroplating solution, zinc-based electroplating solution, and lanthanum-based electroplating solution. The following examples take the nickel-based electroplating solution as an example. This nickel-based electroplating solution contains at least the following concentrations of components: nickel sulfate 180 g / L to 280 g / L; nickel chloride 20 g / L to 40 g / L; boric acid 30 g / L to 40 g / L; sodium dodecyl sulfate 0.05 g / L to 0.1 g / L; the pH value is adjusted to 2 to 6 by ammonia water. The specific electroplating solution used is: nickel sulfate 220 g / L; nickel chloride 30 g / L; boric acid 35 g / L; sodium dodecyl sulfate 0.07 g / L; the pH is adjusted to 4 by ammonia water, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Step 4: After the ion-exchange electrodeposition is completed, take out the NdFeB magnet, wash it clean with water and dry it, then a NdFeB magnet with a corrosion-resistant coating formed on its surface is obtained.

[0035] Example 1

[0036] This Example 1 is a surface treatment method for NdFeB magnets. An unmagnetized N40 commercial sintered NdFeB magnet is used as the as-prepared magnet, and it specifically includes the following steps:

[0037] 1. First, place the N40 magnet in an alkaline cleaning solution at 65 °C ± 5 °C and stir for degreasing for 10 min. After cleaning and degreasing, wash it clean with deionized water. The alkaline cleaning formula is NaOH 7.5 g / L; Na 2 CO 3 45 g / L; Na 3 PO 4 50 g / L; emulsifier OP-10 2 g / L; sodium dodecyl sulfate 0.2 g / L;

[0038] 2. Immerse the magnet treated in step 1 in a 6 wt% HNO 3 solution for 30 s, then wash it clean with deionized water; immerse it in a 3 wt% H 2 SO 4 solution for 30 s, wash it clean with deionized water, and then ultrasonically clean it with absolute ethanol for 3 min to obtain a surface-pretreated sintered NdFeB magnet;

[0039] 3. Place the pretreated sintered NdFeB magnet in a nickel-based electrolyte. Connect the magnet to the negative electrode and use a nickel sheet as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C and perform ion-exchange deposition in two stages to deposit nickel on the surface of the sintered NdFeB magnet.

[0040] (1) For the first-stage ion-exchange deposition, apply an external constant magnetic field and a variable-frequency electric field. The magnetic field strength is 3000 gs. The parameters of the variable-frequency electric field include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 600 Hz, the duty cycle is 40%, the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the treatment time is 10 min.

[0041] (2) For the second-stage ion-exchange deposition, adjust the constant magnetic field to a rotating magnetic field, that is, apply a rotating magnetic field and a variable-frequency electric field synchronously. The magnetic field parameters include: the magnetic field strength is 3000 gs, and the rotation speed is 60 rpm / min. The parameters of the variable-frequency electric field include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 600 Hz, the duty cycle is 40%; the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the treatment time is 10 min.

[0042] 4. Finally, place the sintered NdFeB magnet with nickel deposited on its surface in deionized water at 50°C for cleaning, and then dry it in an environment at 60°C to obtain a NdFeB magnet with a corrosion-resistant coating formed on its surface.

[0043] Example 2

[0044] This Example 2 provides a method for surface treatment of NdFeB magnets. The only difference from Example 1 is that the intensities of the constant magnetic field and the rotating magnetic field in the ion-exchange deposition in step 3 are both adjusted to 2000 gs, and other parameters and conditions are the same as those in Example 1.

[0045] Example 3

[0046] This Example 3 provides a method for surface treatment of NdFeB magnets. The only difference from Example 1 is that the intensities of the constant magnetic field and the rotating magnetic field in the ion-exchange deposition in step 3 are both adjusted to 1000 gs, and other parameters and conditions are the same as those in Example 1.

[0047] Example 4

[0048] This Example 4 provides a method for surface treatment of NdFeB magnets. The only difference from Example 1 is that the rotation speed of the rotating magnetic field in the ion-exchange deposition in step 3 is adjusted to 20 rpm / min, and other parameters and conditions are the same as those in Example 1.

[0049] Example 5

[0050] Example 5 provides a surface treatment method for NdFeB magnets. The difference from Example 1 is only that: the rotation speed of the rotating magnetic field in step 3 of ion exchange deposition is adjusted to 100 rpm / min, and other parameters and conditions are the same as those in Example 1.

[0051] Comparative Example 1

[0052] The difference between Comparative Example 1 and Example 2 is that no magnetic field is applied during the entire stage of ion exchange electrodeposition in step 3, and other parameters and conditions are the same as those in Example 2.

[0053] Step 3 of Comparative Example 1 is specifically as follows:

[0054] Place the pretreated sintered NdFeB magnet in a nickel-based electrolyte. The magnet is connected to the negative electrode, and a nickel sheet is used as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C, set the current density of the forward pulse to 8 A / dm 2 , the working frequency is 600 Hz, the duty cycle is 40%, the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the treatment time is 20 min.

[0055] Comparative Example 2

[0056] The difference between Comparative Example 2 and Example 2 is that a constant magnetic field is applied during the entire stage of ion exchange electrodeposition in step 3, and other parameters and conditions are the same as those in Example 2.

[0057] Step 3 of Comparative Example 2 is specifically as follows:

[0058] Place the pretreated sintered NdFeB magnet in a nickel-based electrolyte. The magnet is connected to the negative electrode, and a nickel sheet is used as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C, and apply an external magnetic field and a variable-frequency electric field;

[0059] The magnetic field strength is 2000 gs; the parameters of the variable-frequency electric field include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 600 Hz, the duty cycle is 40%, the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the total treatment time is 20 min.

[0060] Comparative Example 3

[0061] The difference between Comparative Example 3 and Example 2 is that a rotating magnetic field is applied during the entire stage of ion exchange electrodeposition in step 3, and other parameters and conditions are the same as those in Example 2.

[0062] Step 3 of Comparative Example 3 specifically includes:

[0063] Place the pre-treated sintered NdFeB magnet in a nickel-based electrolyte. The magnet is connected to the negative electrode, and a nickel sheet serves as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C, and apply an external rotating magnetic field and a variable-frequency electric field;

[0064] The parameters of the rotating magnetic field include: magnetic field strength of 2000 gs and rotation speed of 60 rpm / min; the parameters of the variable-frequency electric field include: current density of the forward pulse is 8 A / dm 2 , working frequency of 600 Hz, duty cycle of 40%, current density of the reverse pulse is 0.2 A / dm 2 , working frequency of 400 Hz, duty cycle of 20%, and total treatment time of 20 min.

[0065] Comparative Example 4

[0066] The difference between Comparative Example 4 and Example 2 is that a constant magnetic field is applied only in the second stage of ion-exchange electrodeposition in Step 3, and other parameters and conditions are the same as those in Example 2.

[0067] Step 3 of Comparative Example 4 specifically includes:

[0068] Place the pre-treated sintered NdFeB magnet in a nickel-based electrolyte. The magnet is connected to the negative electrode, and a nickel sheet serves as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C, and perform ion-exchange deposition in two stages;

[0069] (1) In the first stage of ion-exchange deposition, only a variable-frequency electric field is applied, and its parameters are: current density of the forward pulse is 8 A / dm 2 , working frequency of 600 Hz, duty cycle of 40%; current density of the reverse pulse is 0.2 A / dm 2 , working frequency of 400 Hz, duty cycle of 20%, and treatment time of 10 min;

[0070] (2) In the second stage of ion-exchange deposition, an external constant magnetic field and a variable-frequency electric field are applied. The magnetic field strength is 2000 gs; the parameters of the variable-frequency electric field include: current density of the forward pulse is 8 A / dm 2 , working frequency of 600 Hz, duty cycle of 40%, current density of the reverse pulse is 0.2 A / dm 2 , working frequency of 400 Hz, duty cycle of 20%, and treatment time of 10 min.

[0071] Comparative Example 5

[0072] The difference between Comparative Example 5 and Example 2 is that a rotating magnetic field is applied only in the second stage of ion-exchange electrodeposition in Step 3, and other parameters and conditions are the same as those in Example 2.

[0073] Step 3 of Comparative Example 5 is specifically as follows:

[0074] Place the pretreated sintered Nd-Fe-B magnet in a nickel-based electrolyte. The magnet is connected to the negative electrode, and a nickel sheet is used as the positive electrode. Control the electrolyte temperature at 45°C ± 5°C and perform ion exchange deposition in two stages;

[0075] (1) In the first stage of ion exchange deposition, only apply a variable-frequency electric field. Its parameters include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 600 Hz, and the duty cycle is 40%; the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the treatment time is 10 min;

[0076] (2) In the second stage of ion exchange deposition, apply an external rotating magnetic field and a variable-frequency electric field. Its magnetic field parameters include: the magnetic field strength is 2000 gs, and the rotation speed is 60 rpm / min; the parameters of the variable-frequency electric field include: the current density of the forward pulse is 8 A / dm 2 , the working frequency is 600 Hz, the duty cycle is 40%, the current density of the reverse pulse is 0.2 A / dm 2 , the working frequency is 400 Hz, the duty cycle is 20%, and the treatment time is 10 min.

[0077] Comparative Example 6

[0078] The difference between this Comparative Example 6 and Example 2 is that the intensities of the constant magnetic field and the rotating magnetic field in step 3 of ion exchange electrodeposition are adjusted to 4000 gs, and other parameters and conditions are the same as those in Example 2.

[0079] At room temperature, use an electrochemical workstation to test the corrosion resistance of the Nd-Fe-B magnets prepared in Examples 1 to 5 and Comparative Examples 1 to 6 in a 3.5% NaCl solution; use an X-ray fluorescence multi-layer thickness gauge to measure the thickness of the coating and calculate the deposition efficiency. Deposition efficiency = coating thickness / total deposition time; the parameter data is shown in Table 1.

[0080] Table 1

[0081]

[0082] The more negative the corrosion potential E corr , the higher the activity and the faster the electrochemical corrosion; the corrosion rate v is proportional to the corrosion current density I corr , and their relationship can be referred to the formula v = A × I corr / (n×F), where A is the atomic weight of the metal to be corroded; n is the chemical valence state of the metal; F is the Faraday constant, and the self-corrosion current density I corr The larger it is, the faster the electrochemical corrosion; the coating impedance value is proportional to the charge transfer resistance R in the equivalent circuit ct The larger the impedance value, the better the corrosion resistance of the coating.

[0083] It can be seen from the data in Table 1 that in Examples 1 to 5 of the present invention, a corrosion-resistant coating with a thickness of more than 20 μm can be rapidly prepared in 20 minutes, greatly improving the deposition efficiency and having strong corrosion resistance. The self-corrosion potential E of each example of the present invention corr increases, the self-corrosion current density decreases, and the charge transfer resistance R ct increases, indicating its excellent corrosion resistance.

[0084] It can be seen from the data of Examples 1 to 3 that as the magnetic field strength increases, the corrosion current density I corr first decreases and then increases. As the magnetic field strength increases, the corrosion resistance of the coating first increases and then decreases, and the deposition rate increases. The reason is that applying a magnetic field in the same direction as the migration direction of nickel ions during nickel deposition can improve the deposition efficiency of nickel ions, but an excessive magnetic field strength may affect the coating quality.

[0085] It can be seen from the data of Examples 1, 4 to 5 that as the magnetic field rotation speed increases, the corrosion current density I corr first decreases and then increases, and the deposition rate increases. The reason is that increasing the magnetic field rotation speed can improve the deposition efficiency, but too high a rotation speed will interfere with the electric field, resulting in a decline in the coating performance.

[0086] It can be seen from the comparison between Comparative Example 1 and Example 2 that without applying a magnetic field, the deposition efficiency of the electroplated coating decreases significantly, and the corrosion resistance also decreases, indicating that a suitable magnetic field can assist in improving the deposition efficiency and performance of the coating.

[0087] It can be seen from the comparison between Comparative Example 2 and Example 2 that when a constant magnetic field is applied during the entire electroplating process, the deposition efficiency of the electroplated coating increases, but the flatness becomes worse, and the corrosion resistance decreases. The reason is that applying a magnetic field throughout the process can help nickel ions migrate to the plating surface of the electrode, but it has an adverse effect on the surface leveling process of current reversal.

[0088] It can be seen from the comparison between Comparative Example 3 and Example 2 that when a rotating magnetic field is applied during the entire electroplating process, the deposition efficiency of the electroplated coating decreases, and the corrosion resistance also decreases, indicating that applying a rotating magnetic field throughout the process is likely to cause defects in the coating and affect the coating performance.

[0089] It can be seen from the comparison between Comparative Example 4 and Example 2 that when a constant magnetic field is applied only in the second stage of electrodeposition, the deposition efficiency of the electroplated layer decreases, the flatness significantly decreases, and the corrosion resistance decreases. The reason is that the applied magnetic field may cause certain interference to the electric field, resulting in a decrease in the flatness of the coating surface, and applying a magnetic field in the second stage will cause the decrease in the flatness of the coating layer that cannot be leveled by the reverse electric field.

[0090] It can be seen from the comparison between Comparative Example 5 and Example 2 that when a rotating magnetic field is applied only in the second stage of electrodeposition, the deposition efficiency of the electroplated layer decreases significantly, and there is little difference in the deposition efficiency compared with Comparative Example 1 without applying a magnetic field. At the same time, the lower coating thickness is also likely to cause a decrease in the coating performance.

[0091] It can be seen from the comparison between Comparative Example 6 and Example 2 that when the magnetic field strength increases to 4000 gs, the deposition efficiency of the electroplated layer increases, the flatness decreases, and the corrosion resistance decreases. The reason is that the excessive variable-frequency magnetic field strength will cause certain interference to the electric field, resulting in a decrease in the coating performance.

[0092] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. A method for surface treatment of NdFeB magnets, characterized in that: The method comprises the following steps: Pre-treating the NdFeB magnets to obtain magnets with clean and rough surfaces to be electroplated; Connecting the magnet to be electroplated to a power source and immersing it in a plating solution, and forming a corrosion-resistant coating on the surface of the magnet to be electroplated by an ion exchange electrodeposition method; The ion exchange electrodeposition method includes two stages. In the first stage, a constant magnetic field and a variable frequency electric field are applied synchronously. In the second stage, a rotating magnetic field and a variable frequency electric field are applied synchronously. The strength of the constant magnetic field and the rotating magnetic field is 1000gs~3000gs, and the speed of the rotating magnetic field is 20rpm / min~100rpm / min. The conditions of the variable frequency electric field include: the current density of the forward pulse is 8A / dm 2 , the operating frequency is 400Hz~800Hz, the duty cycle is 20%~60%; the current density of the reverse pulse is 0.2A / dm 2 , the operating frequency is 400Hz and the duty cycle is 20%.

2. A method for surface treatment of NdFeB magnets according to claim 1, characterized in that: The first stage processing time is 10min~15min; the second stage processing time is 10min~15min.

3. A method for surface treatment of NdFeB magnets according to claim 1, characterized in that: The processing temperature of the ion exchange electrodeposition method is 45°C±5°C.

4. A method for surface treatment of NdFeB magnets according to claim 1, characterized in that: The NdFeB magnet pretreatment specifically includes: First, place the NdFeB magnet in an alkaline cleaning solution at 65℃±5℃, stir to remove the oil stains on the NdFeB magnet, and then clean it with water; Then soak the NdFeB magnet in HNO3 solution for 30s±5s, and then clean it with water; Then, the NdFeB magnet is immersed in the H2SO4 solution for 30s±5s, cleaned with water and then ultrasonically cleaned with anhydrous ethanol to obtain a magnet to be electroplated with a clean and rough surface.

5. A method for surface treatment of NdFeB magnets according to claim 4, characterized in that: The alkaline washing solution comprises NaOH, Na2CO3, Na3PO4, an emulsifier and sodium dodecyl sulfate; the emulsifier is OP-10.

6. Neodymium iron boron magnet, characterized in that: The surface treatment is carried out by the surface treatment method for NdFeB magnets according to any one of claims 1 to 5.

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