Ash remover and its application and phosphating pretreatment process of NdFeB magnets

Abstract

The present invention discloses a deashing agent, its use, and a phosphating pretreatment process for NdFeB magnets. The deashing agent comprises basic carbonate, pyrophosphate, and C5-C25 alkylphenol polyoxyethylene ether. The basic carbonate, pyrophosphate, and C5-C25 alkylphenol polyoxyethylene ether are used in a ratio of 9-11 g:43-55 g:0.042-0.055 mL. The deashing agent has excellent deashing performance, and the NdFeB magnet blocks after deashing have excellent salt spray corrosion protection.

Description

Technical Field

[0001] The invention relates to a dust remover and its application as well as a phosphating pretreatment process for a neodymium iron boron magnet. Background Art

[0002] Sintered NdFeB magnets, a rare earth permanent magnet alloy, are seeing a continued expansion in their applications due to their high coercivity, high remanence, and high magnetic energy product. However, sintered NdFeB magnets also have certain drawbacks. Because they contain a large amount of rare earth elements, they are susceptible to oxidation during manufacturing and use, causing a rapid degradation of their magnetic properties. This increases production costs and places extremely stringent demands on controlling oxygen levels during production. Therefore, improving the corrosion resistance of sintered NdFeB magnets is essential for further promoting their use in both industrial production and everyday life.

[0003] Methods for forming coatings on the surface of NdFeB magnets include phosphating, electroplating, chemical plating, electrophoresis, and sputtering. The phosphating process involves placing the NdFeB magnet in a phosphate solution, which reacts with the magnet surface to form a phosphate film. This film is generally gray and insoluble in water, improving the magnet's water absorption and corrosion resistance. It can be used alone for short-term corrosion resistance requirements or in applications with less stringent environmental requirements. To improve product quality and stability, pretreatment of the NdFeB magnet prior to phosphating is necessary. The phosphating pretreatment process of NdFeB magnets generally includes pickling, which is an important step in the pretreatment process of NdFeB magnets. However, after pickling, a dark, loose ash layer will remain on the surface of the NdFeB magnets. Before the subsequent phosphating coating treatment, this loose ash layer must be removed from the magnet surface, that is, de-ashing, otherwise it will have an adverse effect on the density and bonding strength of the subsequent coating.

[0004] CN106435678A discloses a method and apparatus for pre-treatment of NdFeB magnets by electroplating. The method involves uniformly mixing a sintered NdFeB magnet with an appropriate amount of steel balls and placing the mixture in a specific drum. The drum then rotates to perform a series of pre-treatment steps, including ultrasonic chemical degreasing, hot water washing, nitric acid pickling, primary water washing, chemical ash removal, ultrasonic water washing, and secondary water washing. The surface is then plated with a nickel-copper nickel coating. Chemical ash removal is performed using an oxalic acid solution.

[0005] CN111321441A discloses a pretreatment process for fully automatic zinc plating of NdFeB, including automatic pickling with a 2% nitric acid solution; deashing the product after the automatic pickling process, using a drum for deashing; and a first secondary countercurrent water wash of the deashed product. The patent document does not mention a deashing agent.

[0006] CN113846360A discloses a zinc plating process for NdFeB magnets, including the following steps: S1) degreasing: immersing the NdFeB magnets in a heated degreasing solution, rinsing them with water, then immersing them in the degreasing solution again while ultrasonically degreasing them to obtain degreasing NdFeB magnets; S2) pickling and deashing: immersing them in a room-temperature pickling solution, stirring, rinsing, draining, and then electrolytically treating them in a deashing agent to obtain deashed NdFeB magnets; and S3) nickel and zinc plating steps. This patent document uses a deashing agent containing HN-RG.

[0007] CN115537825A discloses an ultrasonic dust remover, its preparation method, and application. The ultrasonic dust remover comprises: 0.0001-2 parts of an antioxidant; 0.0001-6 parts of a complexing agent; 0.000001-1 part of a surfactant; and the balance is water. The antioxidant is preferably one or more of sodium nitrite, sodium benzoate, sodium hydroxide, and potassium hydroxide; the complexing agent is preferably one or more of citric acid, potassium citrate, triethanolamine, triethanolamine borate, and modified borate; and the surfactant is preferably one or more of sodium 2-ethylhexyl sulfate, sodium succinate, polyoxyethylene octylphenol ether, and sodium lauryl sulfate. Summary of the Invention

[0008] In view of this, one object of the present invention is to provide a deashing agent for the pre-phosphating treatment of NdFeB magnets. This deashing agent has excellent deashing performance. Furthermore, the deashed product exhibits excellent salt spray corrosion resistance. Another object of the present invention is to provide a process for the pre-phosphating treatment of NdFeB magnets. Yet another object of the present invention is to provide a use of the deashing agent in the pre-phosphating treatment of NdFeB magnets.

[0009] In one aspect, the present invention provides a ash remover for pre-phosphating treatment of NdFeB magnets, the ash remover comprising: basic carbonate, pyrophosphate and C5-C25 alkylphenol polyoxyethylene ether;

[0010] The usage ratio of basic carbonate, pyrophosphate and C5-C25 alkylphenol polyoxyethylene ether is 9-11 g:43-55 g:0.042-0.055 mL.

[0011] According to the deashing agent of the present invention, preferably, the deashing agent is an aqueous solution; in the aqueous solution, the concentration of basic carbonate is 9-11 g / L; the concentration of pyrophosphate is 43-55 g / L; and the concentration of C5-C25 alkylphenol polyoxyethylene ether is 0.042-0.055 mL / L.

[0012] According to the deashing agent of the present invention, preferably, the number of carbon atoms in the alkyl group of the C5-C25 alkylphenol polyoxyethylene ether is 8-15; the basic carbonate is a basic carbonate of an alkali metal; and the pyrophosphate is a pyrophosphate of an alkali metal.

[0013] According to the deashing agent of the present invention, preferably, the basic carbonate is selected from one or more of sodium carbonate and potassium carbonate; and the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate.

[0014] According to the deashing agent of the present invention, preferably, the basic carbonate is sodium carbonate; and the pyrophosphate is potassium pyrophosphate.

[0015] According to the deashing agent of the present invention, preferably, the C5-C25 alkylphenol polyoxyethylene ether is selected from one or more of octylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether.

[0016] On the other hand, the present invention provides a phosphating pretreatment process for NdFeB magnets, comprising the following steps:

[0017] 1) Degreasing step: Use YB-5 detergent aqueous solution to degrease the NdFeB magnet block;

[0018] 2) Primary water washing step;

[0019] 3) Pickling step;

[0020] 4) Secondary water washing step;

[0021] 5) Deashing step: Deashing is performed using the deashing agent described above;

[0022] 6) Three-stage water washing step.

[0023] According to the phosphating pretreatment process of NdFeB magnets of the present invention, preferably, in step 1), a 0.8-1.2 wt% YB-5 detergent aqueous solution is used for degreasing; and in step 3), a 1-5 wt% nitric acid solution is used for washing.

[0024] According to the phosphating pretreatment process of NdFeB magnets of the present invention, preferably, step 5) includes the following process:

[0025] (i) placing a deashing agent into a deashing tank; an ultrasonic generator is provided on the inner wall of the deashing tank;

[0026] (ii) placing the NdFeB magnet block to be deashed into a deashing tank, wherein the NdFeB magnet block is immersed in an aqueous solution of a deashing agent;

[0027] (iii) Turn on the ultrasonic generator to remove dust for 200 to 300 seconds.

[0028] On the other hand, the present invention provides a use of a dust remover in the pre-phosphating treatment of NdFeB magnets, wherein the dust remover comprises: basic carbonate, pyrophosphate and C5-C25 alkylphenol polyoxyethylene ether; wherein the usage ratio of basic carbonate, pyrophosphate and C5-C25 alkylphenol polyoxyethylene ether is 9-11 g:43-55 g:0.042-0.055 mL.

[0029] The NdFeB magnet pre-phosphating deashing agent of the present invention is effective in cleaning and deashing NdFeB magnet blocks after pickling, resulting in a bright and dust-free appearance. Furthermore, the NdFeB magnet blocks after deashing of the present invention have a good salt spray corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a photograph of the appearance of the NdFeB magnet block after dust removal according to Application Example 1 of the present invention.

[0031] Figure 2 This is a photograph of the appearance of the NdFeB magnet block after dust removal according to Comparative Example 1 of the present invention.

[0032] Figure 3 This is a photograph of the appearance of the NdFeB magnet block after dust removal according to Comparative Example 2 of the present invention.

[0033] Figure 4 This is a diagram showing the salt spray resistance of the NdFeB magnet block after dust removal according to Application Example 1 of the present invention.

[0034] Figure 5 This is a diagram showing the salt spray resistance of the NdFeB magnet block after dust removal according to Application Comparative Example 1 of the present invention.

[0035] Figure 6 This is a diagram showing the salt spray resistance of the NdFeB magnet block after dust removal according to Application Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0037] <Deash remover for NdFeB magnet phosphating pretreatment>

[0038] The present invention provides a deashing agent for pre-phosphating treatment of NdFeB magnets, comprising a basic carbonate, a pyrophosphate, and a C5-C25 alkylphenol polyoxyethylene ether. The basic carbonate, pyrophosphate, and C5-C25 alkylphenol polyoxyethylene ether are used in a ratio of 9-11 g:43-55 g:0.042-0.055 mL. This deashing agent provides excellent deashing performance, resulting in a bright, dust-free appearance for the deashed NdFeB magnet blocks. Furthermore, it improves the salt spray resistance of the deashed NdFeB magnet blocks.

[0039] In the present invention, the deashing agent comprises basic carbonate, pyrophosphate, C5-C25 alkylphenol polyoxyethylene ether, and water. The deashing agent is an aqueous solution. In certain specific embodiments, the deashing agent consists solely of basic carbonate, pyrophosphate, C5-C25 alkylphenol polyoxyethylene ether, and water.

[0040] According to one embodiment of the present invention, in the aqueous solution of the deashing agent, the concentration of basic carbonate is 9-11 g / L; the concentration of pyrophosphate is 43-55 g / L; and the concentration of C5-C25 alkylphenol polyoxyethylene ether is 0.042-0.055 mL / L.

[0041] In the aqueous solution of the deashing agent, the concentration of the basic carbonate may be 9 to 11 g / L, preferably 9.5 to 10.5 g / L, and more preferably 10 to 10.3 g / L. The concentration of the pyrophosphate may be 43 to 55 g / L, preferably 48 to 53 g / L, and more preferably 49 to 50 g / L. The concentration of the C5 to C25 alkylphenol polyoxyethylene ether may be 0.042 to 0.055 mL / L, preferably 0.045 to 0.053 mL / L, and more preferably 0.048 to 0.050 mL / L.

[0042] In the present invention, the basic carbonate may be an alkali metal basic carbonate. The basic carbonate is selected from one or more of sodium carbonate and potassium carbonate; preferably, the basic carbonate is selected from sodium carbonate or potassium carbonate. More preferably, the basic carbonate is sodium carbonate.

[0043] In the present invention, the pyrophosphate may be an alkali metal pyrophosphate. The pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; preferably, the pyrophosphate is selected from sodium pyrophosphate or potassium pyrophosphate. More preferably, the pyrophosphate is potassium pyrophosphate.

[0044] The number of carbon atoms in the alkyl group of the C5-C25 alkylphenol polyoxyethylene ether is 5-25, preferably 8-15, and more preferably 8-10. The C5-C25 alkylphenol polyoxyethylene ether is selected from one or more of octylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether. Preferably, the C5-C25 alkylphenol polyoxyethylene ether is a combination of octylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether. According to one embodiment of the present invention, the C5-C25 alkylphenol polyoxyethylene ether is OP-10.

[0045] In certain embodiments, the aqueous solution of the deashing agent has a sodium carbonate concentration of 9 to 11 g / L, a potassium pyrophosphate concentration of 43 to 55 g / L, and an OP-10 concentration of 0.042 to 0.055 mL / L. The present inventors surprisingly discovered that controlling the concentrations of sodium carbonate, potassium pyrophosphate, and OP-10 within specific ranges results in better deashing effects on NdFeB magnet blocks, resulting in a bright, post-deash appearance.

[0046] Pyrophosphate, basic carbonate and C5-C25 alkylphenol polyoxyethylene ether are uniformly mixed in water to obtain a deashing agent.

[0047] <NdFeB magnet phosphating pretreatment process>

[0048] The present invention also provides a phosphating pretreatment process for NdFeB magnets, comprising the following steps:

[0049] 1) Degreasing step; 2) Primary water washing step; 3) Pickling step; 4) Secondary water washing step; 5) Ash removal step; 6) Tertiary water washing step.

[0050] In step 1), the NdFeB magnet block is degreased using a 0.8-1.2 wt% YB-5 detergent aqueous solution. The degreasing time may be 160-210 seconds, preferably 170-200 seconds, and more preferably 180-190 seconds.

[0051] The concentration of the YB-5 detergent aqueous solution can be 0.8-1.2 wt %, preferably 0.9-1.2 wt %, and more preferably 1.0-1.1 wt %. This can improve the degreasing effect. YB-5 detergent is a commercially available product.

[0052] In step 2), the primary water washing step includes a primary water wash and a secondary water wash. Both washes are countercurrent washes. The primary water wash is performed with hot water at 55-65°C for 50-70 seconds. The secondary water wash is performed with hot water at 55-65°C for 10-50 seconds.

[0053] In step 3), washing with a nitric acid solution is performed for 40 to 80 seconds, preferably 50 to 75 seconds, and more preferably 55 to 65 seconds. The concentration of the nitric acid solution can be 1 to 5 wt %, preferably 1.5 to 4.5 wt %, and more preferably 2.2 to 3.5 wt %. This facilitates subsequent phosphating treatment.

[0054] In step 4), the secondary water washing is carried out at 20-40° C. for 10-50 seconds. The washing time is preferably 15-45 seconds, more preferably 20-35 seconds.

[0055] In step 5), the ash removal agent described above is used for ash removal. (i) An aqueous solution of the ash removal agent described above is placed in a ash removal tank; wherein an ultrasonic generator is provided on the inner wall of the ash removal tank; (ii) The NdFeB magnet blocks to be ash removed (i.e., NdFeB magnet blocks after acid washing and water washing) are placed in the ash removal tank; wherein the aqueous solution of the ash removal agent covers the NdFeB magnet blocks; and (iii) the ultrasonic generator is activated to perform ash removal for 200-300 seconds.

[0056] In the present invention, the NdFeB magnet block may be a NdFeB magnet with a rectangular parallelepiped or cylindrical structure.

[0057] In the present invention, the dust removal device may also include a movable and rotatable roller, with multiple grooves provided on one side of the roller. One end of the NdFeB magnet block matches the groove and can be embedded in the groove. In this way, by moving the roller, the NdFeB magnet block is immersed in the dust removal agent aqueous solution in the dust removal tank.

[0058] In step 6), the three-stage water washing step may include an initial water washing step of 10 to 50 seconds, an ultrasonic water washing step of 60 seconds, and a further water washing step of 10 to 50 seconds, which is beneficial for subsequent phosphating.

[0059] The NdFeB magnet block obtained by the phosphating pre-treatment process of the present invention is conducive to subsequent phosphating and makes the bonding force between the coating layer obtained by phosphating and the NdFeB magnet block higher.

[0060] <Purpose>

[0061] The present invention also provides a use of a dust remover in the pre-phosphating treatment of NdFeB magnets, and in particular provides a use of a dust remover in the dust removal step after the pickling step of the pre-phosphating treatment of NdFeB magnets. The dust remover comprises: basic carbonate, pyrophosphate, and C5-C25 alkylphenol polyoxyethylene ether; wherein the usage ratio of the three is 9-11g:43-55g:0.042-0.055mL. Preferably, the dust remover is an aqueous solution; in the aqueous solution, the concentration of basic carbonate is 9-11g / L; the concentration of pyrophosphate is 43-55g / L; and the concentration of C5-C25 alkylphenol polyoxyethylene ether is 0.042-0.055mL / L. The detailed introduction of the dust remover is mentioned above and will not be repeated here.

[0062] The following describes the raw material sources and analysis methods of the embodiments, comparative examples and application examples:

[0063] Source of OP-10: Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.

[0064] Neutral salt spray test method: Test according to GB-T-10125-2021 Artificial atmosphere corrosion test salt spray test.

[0065] Salt water test method: Use 3wt% sodium chloride solution and completely immerse the magnets in salt water at room temperature. The magnets must be separated from each other and there must be no overlapping or tight contact. Then observe the rust condition of the magnets.

[0066] Example 1

[0067] Mix sodium carbonate, potassium pyrophosphate, and OP-10 in water to form a deashing agent. The concentration of sodium carbonate is 10g / L, the concentration of potassium pyrophosphate is 50g / L, and the concentration of OP-10 is 0.048ml / L.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that in the formed deashing agent, the concentration of sodium carbonate is 5 g / L, the concentration of potassium pyrophosphate is 25 g / L, and the concentration of OP-10 is 0.024 ml / L.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that in the formed deashing agent, the concentration of sodium carbonate is 7.5 g / L, the concentration of potassium pyrophosphate is 37.5 g / L, and the concentration of OP-10 is 0.036 ml / L.

[0072] Application Example 1

[0073] The phosphating pretreatment process of NdFeB magnets includes the following steps:

[0074] The sintered NdFeB magnet blocks were degreased with a 1wt% YB-5 detergent aqueous solution at room temperature for 180s. The degreased NdFeB magnet blocks were washed once with 60°C hot water for 60s, and then washed twice with 55°C hot water for 30s. The NdFeB magnet blocks after the second water washing were pickled with a 2.5wt% nitric acid solution for 50s. The pickled NdFeB magnet blocks were subjected to a secondary water washing at room temperature for 20s. The NdFeB magnet blocks after the secondary water washing were placed in a ash removal tank containing the ash removal agent prepared in Example 1, and the ultrasonic generator was turned on for ash removal for 240s. The deashed NdFeB magnet blocks were subjected to a tertiary water washing at room temperature. The appearance of the deashed NdFeB magnet blocks is as follows: Figure 1 shown.

[0075] Application Comparative Example 1

[0076] The difference from Application Example 1 is that in the ash removal step, the NdFeB magnet block after secondary water washing is placed in the ash removal tank containing the ash removal agent prepared in Comparative Example 1, and the ultrasonic generator is turned on for ash removal. The appearance of the NdFeB magnet block after ash removal is as follows: Figure 2 shown.

[0077] Application Comparative Example 2

[0078] The difference from Application Example 1 is that in the ash removal step, the NdFeB magnet block after secondary water washing is placed in the ash removal tank containing the ash removal agent prepared in Comparative Example 2, and the ultrasonic generator is turned on for ash removal. The appearance of the NdFeB magnet block after ash removal is as follows: Figure 3 shown.

[0079] In addition, the ash-removed NdFeB magnet blocks obtained in Application Example 1, Application Comparative Example 1, and Application Comparative Example 2 were subjected to neutral salt spray and salt water tests for verification.

[0080] There was no rust after 4 hours of salt water test, and the salt water corrosion resistance met the product requirements.

[0081] Neutral salt spray test 60min. Figures 4 to 6 The comparison shows that the 60-min salt spray test of the NdFeB magnet block after dust removal obtained in Example 1 is more resistant to salt spray (see Figure 4 ). Figure 5 and Figure 6 The diagram shows the salt spray resistance of the NdFeB magnet blocks after dust removal according to Comparative Example 1 and Comparative Example 2.

[0082] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A deashing agent for NdFeB magnet phosphating pretreatment, wherein the NdFeB magnet phosphating pretreatment process comprises a degreasing step, a primary water washing step, a pickling step, a secondary water washing step, and a deashing step, characterized in that: In the deashing step, deashing is performed using the deashing agent; The deashing agent consists only of basic carbonate, pyrophosphate, C5-C25 alkylphenol polyoxyethylene ether and water; The deashing agent is an aqueous solution; in the aqueous solution, the concentration of basic carbonate is 9-11 g / L; the concentration of pyrophosphate is 43-55 g / L; the concentration of C5-C25 alkylphenol polyoxyethylene ether is 0.042-0.055 mL / L; The basic carbonate is selected from one or more of sodium carbonate and potassium carbonate; the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the C5-C25 alkylphenol polyoxyethylene ether is selected from one or more of octylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether.

2. The dust remover according to claim 1, characterized in that The basic carbonate is sodium carbonate; the pyrophosphate is potassium pyrophosphate; and the C5-C25 alkylphenol polyoxyethylene ether is OP-10.

3. A phosphating pretreatment process for NdFeB magnets, characterized in that: The steps include: 1) Degreasing step: Use YB-5 detergent aqueous solution to degrease the NdFeB magnet block; 2) Primary water washing step; 3) Pickling step; 4) Secondary water washing step; 5) Deashing step: Deashing using the deashing agent according to any one of claims 1 to 2; 6) Three-stage water washing step.

4. The phosphating pretreatment process for NdFeB magnets according to claim 3, wherein: In step 1), degreasing is performed using a 0.8-1.2 wt% YB-5 detergent aqueous solution; In step 3), washing is performed using a 1-5 wt% nitric acid solution.

5. The phosphating pretreatment process for NdFeB magnets according to claim 4, wherein: Step 5) includes the following process: (i) placing a deashing agent into a deashing tank; an ultrasonic generator is provided on the inner wall of the deashing tank; (ii) placing the NdFeB magnet block to be deashed into a deashing tank, wherein the NdFeB magnet block is immersed in an aqueous solution of a deashing agent; (iii) Turn on the ultrasonic generator to remove dust for 200 to 300 seconds.

6. A use of a dust removal agent in the pre-phosphating treatment of NdFeB magnets, wherein the pre-phosphating treatment process of NdFeB magnets comprises a degreasing step, a primary water washing step, an acid washing step, a secondary water washing step, and a dust removal step, characterized in that: In the deashing step, the deashing agent is used for deashing; The deashing agent consists only of basic carbonate, pyrophosphate, C5-C25 alkylphenol polyoxyethylene ether and water; The deashing agent is an aqueous solution; in the aqueous solution, the concentration of basic carbonate is 9-11 g / L; the concentration of pyrophosphate is 43-55 g / L; the concentration of C5-C25 alkylphenol polyoxyethylene ether is 0.042-0.055 mL / L; The basic carbonate is selected from one or more of sodium carbonate and potassium carbonate; the pyrophosphate is selected from one or more of sodium pyrophosphate and potassium pyrophosphate; the C5-C25 alkylphenol polyoxyethylene ether is selected from one or more of octylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether.

Images