A nitric acid-free pickling solution for neodymium-iron-boron material, and a preparation method and application thereof

Abstract

The application belongs to the technical field of surface treatment of magnetic materials, and particularly relates to a nitric acid-free pickling solution for neodymium iron boron materials and a preparation method and application thereof, which comprises square acid, pararosolic acid, ethylenediaminetetraacetic acid, sodium polyoxyethylene lauryl ether sulfate, decyl polyoxyethylene lauryl ammonium bromide and water. The nitric acid-free pickling solution for neodymium iron boron materials provided by the application does not contain strong-smoke acid and phosphorus components, is friendly to the environment, will not produce corrosive acid mist in production and use, and is safe to operate under mild conditions. The operation process is simple, has no obvious corrosion or discoloration on the metal substrate, can effectively remove oxides, grease and impurities on the surface of the neodymium iron boron material, and maintains the quality and performance of the material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of surface treatment of magnetic materials, and particularly relates to a nitric acid-free pickling solution for neodymium iron boron materials and a preparation method and application thereof. BACKGROUND

[0002] Neodymium iron boron material is a kind of permanent magnet material with high magnetic energy product and good magnetic properties, which is widely used in the fields of motors, generators, computer hard disks, etc. However, neodymium iron boron material is easily affected by oxidation, pollution and other problems during preparation, resulting in the decline of material performance. The traditional surface treatment method of neodymium iron boron material mainly includes steps of pickling, alkaline cleaning, activation, coating, etc. However, the neodymium iron boron material after alkaline cleaning performs poorly in some corrosive environments, is easily eroded and damaged by chemicals, and limits its application in certain fields. In addition, the magnetic properties of the neodymium iron boron material after alkaline cleaning will obviously decay at high temperature, which limits its application in high temperature environment. Although pickling is a common surface treatment method, which can remove the oxides and impurities on the surface of neodymium iron boron material and improve the purity and surface quality of the material. However, hydrochloric acid, nitric acid and other acids are often used as pickling solution in traditional pickling method, and nitric acid is highly toxic and corrosive, which has great harm to the environment and human health. Therefore, it is of great significance to find a nitric acid-free pickling solution.

[0003] Chinese patent CN 112921329 A discloses a kind of alkaline cleaning solution for neodymium iron boron material and cleaning method of neodymium iron boron material, including the following mass percentage of raw materials: sodium hydroxide 0.5-2%, sulfonic acid 0.5-1.5%, fatty alcohol polyoxyethylene ether sodium sulfate 1-3%, oil removal agent 2-5%, water 91.5-97%. The cleaning solution is cleaned at 90-100℃ for 20-30 minutes, which makes the surface of the cleaned neodymium iron boron permanent magnet bright and clean, and causes little damage to the neodymium iron boron permanent magnet during cleaning, ensuring the integrity of the neodymium iron boron permanent magnet. However, the high content of fatty alcohol polyoxyethylene ether sodium sulfate in the cleaning solution will cause residues on the surface of the magnetic material, affecting the physical properties of the magnetic material. In addition, the high temperature in the operation process and the complex process cannot guarantee the production efficiency.

[0004] Chinese patent CN 100385042C discloses a neodymium iron boron magnetic material surface oil removal cleaning agent and use method, by weight parts consisting of: in each liter of solution sodium hydroxide is 5-10g, sodium carbonate is 15-30g, trisodium phosphate is 30-50g, sodium pyrophosphate is 10-15g, OP-10 emulsifier is 1-3g, sodium dodecyl sulfate is 1-2g, thiourea is 0.5-1.5g. Although the process of this alkaline neodymium iron boron cleaning agent is simple, it has a certain cleaning effect. But the surface of the cleaned neodymium iron boron material will have residual metal dust, which is difficult to clean thoroughly, and the effect of the subsequent process is poor, the adhesion after electroplating is poor, and it is difficult to achieve the ideal effect.

[0005] Therefore, for the existing cleaning solution of neodymium iron boron material, how to achieve no dust, no obvious corrosion and other appearance defects after cleaning, the material surface needs to be rust-proof, wear-resistant, heat-resistant, cold-resistant, weather-resistant, surface finish, cannot affect the adhesion of subsequent plating layer, the product does not contain nitric acid, strong alkali, phosphorus and environmental pollutants is a technical problem to be solved in the art. SUMMARY

[0006] The purpose of the present application is to provide a nitric acid-free pickling solution for neodymium iron boron material and its preparation method and application, which does not contain harmful ingredients such as nitric acid, strong alkali, phosphorus and environmental pollutants, is friendly to the environment, does not have obvious corrosion and discoloration to the substrate, the metal surface cleaned with the pickling solution is corrosion-resistant, rust-proof, wear-resistant, heat-resistant, cold-resistant, weather-resistant, has strong surface finish, no dust, can retain the color of the substrate itself and improve the brightness, and does not affect the adhesion of subsequent plating layer.

[0007] In order to solve the above technical problems, the present application adopts the following technical scheme:

[0008] A nitric acid-free pickling solution for neodymium iron boron material, comprising square acid, sub-tartaric acid, ethylenediaminetetraacetic acid, surfactant and deionized water.

[0009] Square acid: square acid is an organic acid with good chelating properties, which can react with the oxides and impurities on the surface of neodymium iron boron metal, thereby removing them. Square acid is one of the main cleaning components in the nitric acid-free pickling solution.

[0010] Sub-tartaric acid: sub-tartaric acid is also an organic acid with good chelating properties and mild cleaning effect. It can react with the oxides and impurities on the surface of neodymium iron boron material and dissolve or decompose them. Sub-tartaric acid is one of the synergistic cleaning components in the nitric acid-free pickling solution.

[0011] EDTA: EDTA is a complexing agent that can form stable complexes with metal ions. In the nitric acid-free pickling solution, EDTA can complex with metal ions on the surface of the neodymium iron boron material, thereby stabilizing the metal ions and preventing their redeposition on the material surface.

[0012] Preferably, the surfactant includes sodium polyoxyethylene lauryl ether sulfate and decyl polyoxyethylene lauryl ammonium bromide complex.

[0013] Sodium polyoxyethylene lauryl ether sulfate: Sodium polyoxyethylene lauryl ether sulfate is a surfactant with good interfacial activity and dispersion performance. It can reduce the surface tension of the liquid, making the pickling solution more easily contact with the surface of the neodymium iron boron material, and effectively dispersing the contaminants on the material surface.

[0014] Decyl polyoxyethylene lauryl ammonium bromide: Decyl polyoxyethylene lauryl ammonium bromide is also a cationic surfactant that can form a charged adsorption layer on the material surface with the solution molecules in the pickling solution, adsorb the metal dust on the metal surface, improve the contact effect of the pickling solution with the material surface, and enhance the cleaning effect.

[0015] The present application is a nitric acid-free pickling solution for neodymium iron boron materials. The cleaning mechanism and the role of each component in removing oil and metal dust, as well as the mechanism of the synergistic effect of each component, are a complex and interrelated process. First, neodymium iron boron materials are often affected by oil and metal dust during preparation and processing. These impurities adhere to the surface of the material, affecting its performance and quality. The purpose of the nitric acid-free pickling solution is to remove these impurities through chemical reactions and physical effects, thereby achieving the purpose of purifying the surface of the material. The formic acid and tartaric acid in the pickling solution play a major role in removing oil. Formic acid and tartaric acid are acidic substances with good corrosive and dissolving properties, which can chemically react with the oil and organic matter on the metal surface, breaking it down and dissolving it. On the other hand, the sodium polyoxyethylene dodecyl ether sulfate and decyl polyoxyethylene dodecyl ammonium bromide in the pickling solution play a role in removing metal dust, while also quickly removing the oil and organic matter that has been broken down and dissolved. These two surfactants have strong surface activity, which is further enhanced through compounding, allowing them to disperse and emulsify the metal surface dust particles, making them easier to remove. In addition, the ethylenediaminetetraacetic acid (EDTA) in the nitric acid-free pickling solution acts as a complexing agent. Under the action of acidic substances, some metal ions are released, and EDTA can form stable complexes with metal ions, reducing corrosion of the metal surface and improving the cleaning effect of the pickling solution. Through synergistic matching of the components, their respective advantages are realized, achieving efficient cleaning of the surface of neodymium iron boron materials, ensuring the quality of the materials and the adhesion of subsequent coatings, while also having environmental performance and cleaning effects.

[0016] The combination of formic acid and tartaric acid with surfactants such as sodium polyoxyethylene dodecyl ether sulfate and decyl polyoxyethylene dodecyl ammonium bromide improves the permeability and cleaning effect of the pickling solution. EDTA as a complexing agent can form complexes with metal ions, reducing corrosion of the metal surface and improving the cleaning effect of the pickling solution. Deionized water acts as a solvent and diluent, ensuring the stability and safety of the pickling solution.

[0017] The use of the above substances in combination can achieve the following effects: 1. Reduce surface tension: the pickling solution is more easily contacted with the cleaned surface and penetrates into the tiny cracks, pores and interior of the cleaned material. 2. Increase the fluidity of the liquid: surfactants can increase the fluidity of the pickling solution, making it more evenly distributed on the cleaned surface, thereby more effectively penetrating into the surface. 3. Improve the wettability of the solution: the liquid can more easily wet the surface and penetrate into it. 4. Improve the dispersibility of the liquid: the various components in the pickling solution are more evenly distributed, thereby helping to more effectively penetrate into various parts of the cleaned surface.

[0018] Preferably, the components include the following mass parts of components:

[0019] the formic acid: 20-24 parts;

[0020] the tartronic acid: 1-4 parts;

[0021] the ethylenediaminetetraacetic acid: 1-4 parts;

[0022] the sodium polyoxyethylene lauryl ether sulfate: 1-4 parts;

[0023] the decyl polyoxyethylene lauryl bromide ammonium: 1-4 parts;

[0024] deionized water: 60-76 parts.

[0025] Preferably, the components include the following mass parts of components:

[0026] the formic acid: 23 parts;

[0027] the tartronic acid: 3 parts;

[0028] the ethylenediaminetetraacetic acid: 3 parts;

[0029] the sodium polyoxyethylene lauryl ether sulfate: 3 parts;

[0030] the decyl polyoxyethylene lauryl bromide ammonium: 3 parts;

[0031] deionized water: 65 parts.

[0032] A preparation method of the above nitric acid-free pickling solution for neodymium iron boron material, comprising the following steps:

[0033] (1) add part of deionized water in a container, stir, add the formic acid, the tartronic acid, and continue to stir until completely dissolved;

[0034] (2) add the ethylenediaminetetraacetic acid, the sodium polyoxyethylene lauryl ether sulfate, and stir until completely dissolved;

[0035] (3) reduce the temperature, add the decyl polyoxyethylene lauryl bromide ammonium, and stir until completely dissolved;

[0036] (4) add the remaining deionized water to the total volume of the solution, stir well, and obtain the nitric acid-free pickling solution for neodymium iron boron material.

[0037] Preferably, in steps (1) and (4), the volume ratio of the amount of deionized water added is 3:4; in step (1), the stirring temperature is 10-15°C, and the stirring rate is 80-100 r / min; in step (3), the temperature is reduced to 5°C.

[0038] In step (1), the main reason for maintaining low temperature is to control the reaction rate. Too high temperature can cause two adverse effects:

[0039] a. Solubility problem: The slow dissolution of the mixture of amines and tartronic acid at low temperature leads to a higher degree of subsequent reaction and a better product. If the temperature is too high, some side reactions may occur, such as the dehydration condensation of tartronic acid itself, etc. During the reaction, oil impurities will be precipitated, affecting the efficiency of the dissolution of the reactants, thus affecting the preparation of the formula.

[0040] b. Too fast reaction rate: In chemical reactions, temperature usually affects the reaction rate. If the temperature is too high, the reaction rate may be too fast, leading to uncontrolled side reactions, thus affecting the quality and purity of the product.

[0041] In step (3), the purpose of further reducing the temperature to 5℃ is to control the process of adding decyl polyoxyethylene dodecyl ammonium bromide. This process may involve some specific reaction mechanisms or dissolution kinetics that need to be carried out at low temperature to ensure the selectivity and efficiency of the reaction. In addition, the chemical reaction is more selective at low temperature, i.e. it is easier to obtain the target product and reduce the generation of by-products, so reducing the temperature can improve the purity and yield of the product.

[0042] An application of the above-mentioned nitric acid-free pickling solution for neodymium iron boron material is used for surface acidification cleaning of neodymium iron boron material.

[0043] Preferably, it comprises the following steps:

[0044] A, surface cleaning of the neodymium iron boron material to obtain a surface cleaned neodymium iron boron material;

[0045] B, ultrasonic water washing of the surface cleaned neodymium iron boron material to obtain a water washed neodymium iron boron material;

[0046] C, diluting the nitric acid-free pickling solution for neodymium iron boron material with deionized water, stirring uniformly to obtain a pickling tank solution;

[0047] D, immersing the water washed neodymium iron boron material in the pickling tank solution and ultrasonic oscillation to obtain a pickled neodymium iron boron material.

[0048] E, water washing and drying of the pickled neodymium iron boron material to obtain a pickled neodymium iron boron material.

[0049] Preferably, in step A, the surface cleaning comprises one or more of oil removal, wax removal; in step B, the power of the ultrasonic water washing comprises 1500-2000w, the time comprises 5min, the operation of step C comprises: diluting the nitric acid-free pickling solution for neodymium iron boron material with deionized water to 10-50 times the volume, stirring uniformly, controlling the temperature at 15-30℃, to obtain the pickling tank solution; in step D, the power of the ultrasonic oscillation comprises 1500-2000w, the time comprises 6-8min; in step E, the drying comprises using a drying oven at 60℃.

[0050] A pickled neodymium iron boron material obtained by the above application.

[0051] Compared with the prior art, the implementation of the present application has the following beneficial effects:

[0052] 1. The pickling solution does not contain harmful components such as nitric acid, strong alkali, phosphorus and environmental pollutants, is environmentally friendly, can effectively reduce environmental pollution, will not produce corrosive acid mist in production and use, and has mild conditions and safe operation. The operation process is simple, there is no obvious corrosion or discoloration on the metal substrate, and the quality and performance of the material can be effectively maintained.

[0053] 2. After cleaning with the pickling solution, the metal surface of the neodymium iron boron material can obtain excellent properties such as corrosion resistance, rust prevention, wear resistance, heat resistance, cold resistance, and weather resistance, and has strong surface finish and no dust, can retain the color of the substrate itself and improve the brightness;

[0054] 3. The pickling solution uses a plurality of components such as formic acid, tartaric acid, ethylenediaminetetraacetic acid, polyoxyethylene dodecyl ether sodium sulfate, decyl polyoxyethylene dodecyl ammonium bromide, etc., and through the synergistic effect of these components, it can efficiently remove oil stains and metal dust on the surface of the neodymium iron boron material, and the cleaning effect is remarkable.

[0055] 4. The pickling solution not only ensures the cleanliness and quality of the metal surface, but also does not affect the adhesion of the subsequent coating, ensuring the stability and reliability of the neodymium iron boron material in the subsequent processing process.

[0056] 5. The pickling solution has no obvious corrosion and discoloration on the substrate, is safe and reliable during use, and will not cause harm to the operator. BRIEF DESCRIPTION OF DRAWINGS

[0057] Fig. 1 A 3D fluorescence electron microscope test result graph of a neodymium iron boron material untreated workpiece.

[0058] Fig. 2 A 3D fluorescence electron microscope test result graph of a neodymium iron boron material workpiece after pickling.

[0059] Fig. 3 Figure for 3D fluorescence electron microscope test result of the neodymium-iron-boron material workpiece of Comparative Example 1. DETAILED DESCRIPTION

[0060] In order to make the technical solutions of the present application easier to understand, the present application will be further described in detail below with specific examples, so that those skilled in the art can better understand and implement the present application, but the examples are not limiting to the present application. Any modification or replacement of the method, step or condition of the present application without departing from the spirit and essence of the present application shall fall within the scope of the present application. If not specifically indicated, the technical means used in the examples are the conventional means well known to those skilled in the art.

[0061] Effect Example 1

[0062] Examples 1-6 and Comparative Examples 1-10 respectively give the composition ratio of the neodymium-iron-boron pickling solution of the present application, which is specifically listed in Table 1, wherein the ingredient values are parts by mass, and the balance is water. In addition, in order to highlight the superiority of each component, in Comparative Example 7, sulfuric acid is replaced with the formula acid, in Comparative Example 8, tartaric acid is replaced with the formula sub-tartaric acid, in Comparative Example 9, sodium dodecyl sulfate (K12) is replaced with the formula polyoxyethylene dodecyl ether sodium sulfate, in Comparative Example 10, dodecyl ammonium bromide (DTAB) is replaced with the formula decyl polyoxyethylene dodecyl ammonium bromide, and all other conditions remain unchanged, a control experiment is carried out.

[0063] Table 1 Formula composition of Examples 1-6 and Comparative Examples 1-10

[0064]

[0065]

[0066] The preparation method of the neodymium-iron-boron pickling solution of Examples 1-6 and Comparative Examples 1-10 above is as follows: 600 ml of deionized water is added to a 2000 ml beaker, stirred uniformly, the temperature is controlled at 10-15℃, the formula acid and the formula sub-tartaric acid are added, and stirred at low temperature until completely dissolved; the ethylenediaminetetraacetic acid and the polyoxyethylene dodecyl ether sodium sulfate are added, and stirred until completely dissolved; the temperature is lowered to 5℃, the decyl polyoxyethylene dodecyl ammonium bromide is added, and stirred until completely dissolved; the remaining required deionized water is added to the total volume of the solution, and stirred uniformly, thereby obtaining the nitric acid-free pickling solution for neodymium-iron-boron materials of the present application.

[0067] Performance test

[0068] In the examples of the present application, the water film breakage test method and the water wetting test method are used to test the cleanliness of the surface of the neodymium-iron-boron material after cleaning in each example, and the scratch test is used to detect the adhesion of the plating layer in the subsequent electroplating process.

[0069] Water film breaking test method: take the baked neodymium iron boron material, wash the surface of the workpiece with flowing water for three to four times, then observe whether the surface of the workpiece is uniformly covered with water film, and estimate the water film coverage.

[0070] Water wetting test method test: take the baked neodymium iron boron material, wash the surface of the workpiece with flowing water for three to four times, dry the surface of the workpiece, drop water droplets on the surface of the neodymium iron boron material, find that the water droplets are scattered on the surface in the form of water film, and observe whether the water droplets roll off when the surface is inclined.

[0071] Coating and plastic spraying coating adhesion: according to the test method described in the national standard GB / T 9286-1998 "cross-cut test for pigments and varnishes", a cross-cut knife is used to cross and vertical each time on the surface of the test piece, 100 square grids of 1mm 2 are obtained on the sample, and the substrate is required to be exposed at the scratch. After cross-cutting, special 3M adhesive tape is pasted on the entire cross-cut area, then the adhesive tape is quickly torn off, repeated for 5 times, and whether the paint film in the cross-cut area falls off is observed with a magnifying glass, and the paint is rated according to the falling off situation.

[0072] The specific test results are shown in Table 2:

[0073] Table 2

[0074]

[0075]

[0076] The neodymium iron boron pickling solution provided by the application, in the pickling process, the combination of the sulfates of sodium and ammonium of polyoxyethylene dodecyl ether and decyl alkyl polyoxyethylene dodecyl bromide and other surfactants improves the permeability and cleaning effect of the pickling solution. EDTA as a complexing agent can form a complex with metal ions, reducing the corrosion of the metal surface and improving the cleaning effect of the pickling solution. Deionized water as a solvent and diluent ensures the stability and safety of the pickling solution. The synergistic effect of the components improves the cleaning efficiency.

[0077] As can be seen from Table 1 and Table 2, due to insufficient addition of the proportion of squaric acid, the cleaning process cannot be thoroughly cleaned, the subsequent water film is poor, and the subsequent plating layer adhesion is poor. Excessive squaric acid causes the workpiece surface to turn white and the workpiece to corrode, resulting in extremely poor subsequent plating layer adhesion. The addition of insufficient sub-rubidium acid and ethylenediaminetetraacetic acid will result in poor water film coverage of the cleaned workpiece, and excessive addition will affect the performance of the subsequent plating layer. The absence or insufficient addition of sodium polyoxyethylene dodecyl ether sulfate and decyl polyoxyethylene dodecyl ammonium bromide will result in a decrease in the emulsification and stripping performance of oil stains during cleaning and the adsorption of metal dust, and the adhesion of the subsequent workpiece coating will be poor. Since the oil stains and metal dust on the surface of the workpiece are emulsified and stripped while being adsorbed and bonded during pickling, the orderly introduction of each component according to a specific proportion can greatly improve the cleaning effect of the workpiece and the subsequent electroplating efficiency.

[0078] The 3D fluorescence electron microscope test results of the Nd-Fe-B material workpiece before and after pickling and after electroplating are shown in Figs. 1-3 Further shown in the attached Figs. 1-3 Further shown in the attached Fig. 1 The original untreated workpiece has more oil stains and dust on the surface, is black and rough, and the surface roughness is 100 nm. Fig. 2 The finished product treated by the optimal ratio has a smooth surface, is silver gray, and the surface roughness is 50 nm. Fig. 3 The finished product treated by Comparative Example 1 has a white surface and corrosive small holes, and the roughness is 110 nm. It is possible that the content in the formula of Comparative Example 1 is too high, because the formula is a strong acidic and corrosive pickling solution. Excessive formula concentration causes serious corrosion on the surface of the workpiece, making the workpiece surface uneven, the color white, and the workpiece severely damaged, affecting the subsequent electroplating and plating layer.

[0079] In addition, in Comparative Example 7, the replacement of the formic acid with sulfuric acid led to adverse effects, which can be due to the strong acidic nature of sulfuric acid. Formic acid and tartaric acid play a role in removing oil and dust in the pickling solution, while the acidity of sulfuric acid can be too strong, leading to excessive corrosion of the surface of the neodymium iron boron material, thereby affecting the cleaning effect. In addition, sulfuric acid can have an adverse chemical reaction with other ingredients, leading to a decrease in the stability of the cleaning solution, thereby affecting the cleaning effect. In Comparative Example 8, the replacement of tartaric acid with tartaric acid led to adverse effects, which can be due to the different chemical properties of tartaric acid. Tartaric acid has certain acidity and complexing properties, which can work synergistically with formic acid to remove oil and dust. While tartaric acid can have an adverse chemical reaction with other ingredients, affecting the cleaning effect of the cleaning solution. In Comparative Example 9, the replacement of polyoxyethylene dodecyl ether sodium sulfate with sodium dodecyl sulfate (K12) led to adverse effects, which can be due to the poor compatibility of sodium dodecyl sulfate with other ingredients. Polyoxyethylene dodecyl ether sodium sulfate has good surface activity, which can effectively disperse and emulsify the dust particles on the surface of the metal, while sodium dodecyl sulfate can not have this property, affecting the cleaning effect of the cleaning solution. In Comparative Example 10, the replacement of decyl polyoxyethylene dodecyl ammonium bromide with dodecyl ammonium bromide (DTAB) led to adverse effects, which can be due to the poor compatibility of dodecyl ammonium bromide (DTAB) with other ingredients. Decyl polyoxyethylene dodecyl ammonium bromide plays a role in dispersion and emulsification in the cleaning solution, while dodecyl ammonium bromide (DTAB) can not achieve the same effect, thereby affecting the cleaning effect of the cleaning solution. In summary, the reasons for these adverse effects in the control experiments can be that the replaced ingredients are not compatible with the ingredients in the original formula in terms of chemical properties, leading to a decrease in the performance of the cleaning solution, thereby affecting the cleaning effect. Therefore, these ingredients cannot be replaced.

[0080] While embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A nitric acid-free pickling solution for neodymium iron boron materials, characterized in that, The components include the following parts by weight: Squamous acid: 23 parts; Tartaric acid: 3 parts; EDTA: 3 parts; Sodium polyoxyethylene dodecyl ether sulfate: 3 parts; Decyl polyoxyethylene dodecyl ammonium bromide: 3 parts; Deionized water: 65 parts.

2. A method for preparing a nitric acid-free pickling solution for NdFeB materials as described in claim 1, characterized in that, Includes the following steps: (1) Add some deionized water to the container, stir, add the squaric acid and the tartaric acid, and continue stirring until completely dissolved; (2) Add the ethylenediaminetetraacetic acid and the sodium polyoxyethylene dodecyl ether sulfate, and stir until completely dissolved; (3) Lower the temperature, add the decyl polyoxyethylene dodecyl ammonium bromide, and stir until completely dissolved; (4) Add the remaining deionized water to the total volume of the solution, stir well, and obtain the nitric acid-free pickling solution for NdFeB materials.

3. The preparation method according to claim 2, characterized in that, In steps (1) and (4), the volume ratio of deionized water added is 3:4; in step (1), the stirring temperature is 10 to 15°C and the stirring rate is 80 to 100 r / min; in step (3), the temperature is reduced to 5°C.

4. The application of the nitric acid-free pickling solution for NdFeB materials as described in claim 1, characterized in that, Used for surface acidification and cleaning of NdFeB materials.

5. The application as described in claim 4, characterized in that, Includes the following steps: A. The surface of the neodymium iron boron material is cleaned to obtain a cleaned neodymium iron boron material; B. The cleaned NdFeB material is subjected to ultrasonic water washing to obtain the washed NdFeB material. C. Dilute the nitric acid-free pickling solution for NdFeB materials with deionized water, stir evenly, and obtain the pickling tank solution; D. Immerse the washed NdFeB material in the pickling tank solution and ultrasonically vibrate to obtain the pickled NdFeB material. E. The acid-washed NdFeB material is washed with water and then dried to obtain acid-washed NdFeB material.

6. The application as described in claim 5, characterized in that, In step A, the surface cleaning includes one or more of degreasing and dewaxing; in step B, the ultrasonic water washing power includes 1500~2000w, and the time includes 5min; the operation in step C includes: diluting the nitric acid-free pickling solution for NdFeB materials with deionized water to 10~50 times the volume, stirring evenly, and controlling the temperature at 15~30℃ to obtain the pickling bath solution; in step D, the ultrasonic vibration power includes 1500~2000w, and the time includes 6~8min; in step E, the drying includes drying in an oven at 60℃.

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