Passivating agent, passivating solution, preparation method and application thereof

Abstract

The present invention discloses a passivating agent, a passivating solution, a preparation method, and applications thereof. The passivating agent comprises 3-10 parts chromium nitrate; 1-5 parts ammonium fluoride; 3-8 parts cobalt nitrate; 2-5 parts sodium nitrate; 0.5-2 parts malonic acid; and 1-5 parts acetic acid. The passivating agent does not contain a surfactant. The passivating agent has a low concentration, mild operating conditions, a short passivation time, and can effectively improve the adhesiveness of the zinc-plated surface of NdFeB.

Description

Technical Field

[0001] The present invention relates to a passivating agent, a passivating solution, a preparation method and an application thereof Background Art

[0002] Neodymium iron boron (NdFeB), also known as NdFeB magnets, is a tetragonal crystal composed of neodymium, iron, and boron. It is manufactured through methods such as powder metallurgy and rotary spray melting. It is widely used in electronic products such as hard drives, mobile phones, headphones, and battery-powered tools. Therefore, NdFeB products are typically small workpieces. To prevent oxidation and corrosion, NdFeB workpieces are generally treated with a galvanizing process, followed by a passivation treatment on the galvanized surface.

[0003] NdFeB requires glue during actual use. If the glue is not firmly bonded, the motor may fall off during use, causing damage. Therefore, the bond strength between the zinc coating and the glue must be strong to avoid adverse effects on the motor's operation. The passivation process of NdFeB in existing technologies is long, inefficient, and the resulting NdFeB coating has poor adhesiveness. Summary of the Invention

[0004] To address the problems of long passivation time and poor surface adhesion after passivation in prior art neodymium iron boron zinc plating, the present invention proposes a passivating agent, a passivating solution, a preparation method, and applications thereof. The passivating agent has a low concentration, mild operating conditions, a short passivation time, and can effectively improve the adhesion of the zinc-plated surface of neodymium iron boron.

[0005] The present invention mainly adopts the following technical solutions to solve the above technical problems:

[0006] The present invention provides a passivating agent, characterized in that it comprises the following components in parts by mass:

[0007] Chromium nitrate, 3-10 parts;

[0008] Ammonium fluoride, 1-5 parts;

[0009] Cobalt nitrate, 3-8 parts;

[0010] Sodium nitrate, 2-5 parts;

[0011] Malonic acid, 0.5-2 parts;

[0012] Acetic acid, 1-5 parts;

[0013] The passivating agent does not contain a surfactant.

[0014] In the present invention, the valence state of chromium in the chromium nitrate is trivalent. The chromium nitrate is preferably chromium nitrate nonahydrate.

[0015] In the present invention, the acetic acid is preferably glacial acetic acid.

[0016] In the present invention, the amount of chromium nitrate is preferably 4 to 9 parts, more preferably 5 to 8 parts, for example 6 parts.

[0017] In the present invention, the amount of ammonium fluoride used is preferably 2 to 4 parts.

[0018] In the present invention, the amount of cobalt nitrate used is preferably 3 to 6 parts, for example 5 parts.

[0019] In the present invention, the amount of sodium nitrate used is, for example, 2 parts or 3 parts.

[0020] In the present invention, the amount of malonic acid used is, for example, 1.5 parts.

[0021] In the present invention, the amount of acetic acid used is, for example, 1.5 parts, 2 parts or 3 parts.

[0022] In the present invention, the mass ratio of the sodium nitrate, cobalt nitrate and chromium nitrate is preferably 1:(0.7-3):(0.7-4), more preferably 1:(1-2):(1-3), for example 1:1.5:1.5.

[0023] In the present invention, the mass ratio of malonic acid to acetic acid is preferably 1:(1-9), more preferably 1:(2-7), for example 1:3.

[0024] In the present invention, the mass ratio of ammonium fluoride to chromium nitrate is preferably 1:(1-8), more preferably 1:(3-6), for example 1:4.

[0025] In the present invention, the mass ratio of ammonium fluoride to malonic acid is preferably 1:(0.5-1.8), more preferably 1:(1-1.6), for example 1.5.

[0026] In a preferred embodiment of the present invention, the mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 3:1:3:2:1.5:2.

[0027] In a preferred embodiment of the present invention, the mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 4:1:2:3:0.5:1.5.

[0028] In a preferred embodiment of the present invention, the mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 6:1:5:3:1.5:3.

[0029] The present invention also provides a passivation solution, characterized in that it comprises the above-mentioned passivating agent and water.

[0030] The concentration of the passivation solution is preferably 10-20 g / L, for example 12.5 g / L or 19.5 g / L, wherein g / L represents the mass of the passivation agent contained in 1 L of the passivation solution, for example, 10 g / L represents 10 g of the passivation agent contained in 1 L of the passivation solution.

[0031] The pH value of the passivation solution is preferably 1.8-2.2, for example 2.0.

[0032] Through experiments, the inventors discovered that the pH value of the passivation solution significantly affects the adhesiveness of the NdFeB zinc-plated surface. The pH value affects the adhesion of the passivation film, which indirectly affects the adhesion of the coating. Both too high and too low pH values can lead to poor adhesion of the passivation film, further deteriorating the adhesion of the coating.

[0033] The present invention also provides a method for preparing the above-mentioned passivation solution, which is characterized by comprising the following steps: dissolving the passivating agent in water to obtain the passivation solution.

[0034] In the present invention, preferably, the passivation solution is prepared by dissolving the passivating agent in a portion of water and then adding the remaining water. More preferably, the passivation solution is prepared by dissolving chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid, and acetic acid in a portion of water in sequence and then adding the remaining water.

[0035] The dissolving method may be conventional in the art, such as stirring.

[0036] The stirring time and method may be conventional in the art, as long as the passivating agent is dissolved.

[0037] Preferably, the method further comprises a stirring step after the addition of the remaining water, wherein the stirring time is preferably 1 to 3 hours, for example 2 hours.

[0038] The present invention also provides a passivation film obtained by passivating the surface of a NdFeB material with the above-mentioned passivation solution, wherein the surface of the NdFeB material is preferably a galvanized surface.

[0039] The present invention also provides a NdFeB material characterized by comprising the above-mentioned passivation film, wherein the NdFeB material is preferably a zinc-plated NdFeB material.

[0040] The present invention also provides an application of the above-mentioned passivating agent or passivating liquid in the environmentally friendly passivation process link of the NdFeB process production line, wherein the passivating agent or passivating liquid is used in the environmentally friendly passivation process link of the NdFeB process production line.

[0041] The environmentally friendly passivation temperature may be room temperature.

[0042] The environmentally friendly passivation time is preferably 5 to 10 seconds, for example 5 seconds or 8 seconds.

[0043] In the present invention, preferably, in the NdFeB process production line, the environmentally friendly passivation process step is after the light output process step.

[0044] In the present invention, preferably, a galvanizing process is further included before the light emitting process.

[0045] The present invention also provides a NdFeB process production line, which uses the above-mentioned passivating agent or passivating liquid in the environmentally friendly passivation process.

[0046] In the present invention, the NdFeB process production line may include the following process flow: loading → degreasing → pickling → ultrasonic deashing → galvanizing → polishing → environmentally friendly passivation → unloading and drying.

[0047] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0048] The reagents and raw materials used in the present invention are commercially available.

[0049] The positive progress effect of the present invention is:

[0050] The passivating agent used in this invention contains no surfactants or hexavalent chromium, operates at low concentrations, and requires mild operating conditions, making it environmentally friendly. It also offers a short passivation time and high passivation efficiency. The tensile strength of the NdFeB surface coating after passivation exceeds 29 MPa.

[0051] In a preferred embodiment of the present invention, the passivating agent can react with the zinc coating on the surface of the NdFeB magnet to form a zinc complex oxide protective film, which greatly improves the corrosion resistance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a process flow chart for Examples 1 to 3 and Comparative Example 1.

[0053] Figure 2 This is a comparison of the adhesiveness of the NdFeB galvanized surface before and after passivation in Example 1. Figure 2 Part a is the adhesiveness diagram of the galvanized surface of NdFeB before passivation. Figure 2 Part b is the adhesiveness diagram of the zinc-plated surface of NdFeB after passivation. DETAILED DESCRIPTION

[0054] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0055] Example 1

[0056] The formula of passivation solution is:

[0057] Chromium nitrate nonahydrate, 3g / L;

[0058] Ammonium fluoride, 1 g / L;

[0059] Cobalt nitrate, 3 g / L;

[0060] Sodium nitrate, 2 g / L;

[0061] Malonic acid, 1.5 g / L;

[0062] Glacial acetic acid, 2 g / L;

[0063] Water, 985ml / L.

[0064] The pH value of the passivation solution is 2.0.

[0065] The preparation method of the passivation solution in this embodiment includes: first adding part of the water to the container, weighing chromium nitrate nonahydrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and glacial acetic acid according to the above formula, adding them to the water in sequence, and stirring until they are completely dissolved in the water; adding the remaining water and continuing to stir for 2 hours.

[0066] The passivation solution of this embodiment is used in the environmentally friendly passivation process of the NdFeB process production line. Figure 1 As shown, specifically: first, the NdFeB raw material is loaded, and after degreasing, pickling, ultrasonic deashing, galvanizing and polishing, the galvanized NdFeB material is obtained. In the environmentally friendly passivation process, the galvanized NdFeB material is placed in the passivation solution, passivated at room temperature for 8s, and then the material is discharged and blown dry to obtain the NdFeB material of this embodiment.

[0067] Example 2

[0068] The formula of passivation solution is:

[0069] Chromium nitrate nonahydrate, 4g / L;

[0070] Ammonium fluoride, 1 g / L;

[0071] Cobalt nitrate, 2 g / L;

[0072] Sodium nitrate, 3 g / L;

[0073] Malonic acid, 0.5 g / L;

[0074] Glacial acetic acid, 1.5 g / L;

[0075] Water, 987ml / L.

[0076] The pH value of the passivation solution is 2.2.

[0077] The preparation method of the passivation solution in this embodiment includes: first adding part of the water to the container, weighing chromium nitrate nonahydrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and glacial acetic acid according to the above formula, adding them to the water in sequence, and stirring until they are completely dissolved in the water; adding the remaining water and continuing to stir for 2 hours.

[0078] The passivation solution of this embodiment is used in the environmentally friendly passivation process of the NdFeB process production line. Figure 1 As shown, specifically: first, the NdFeB raw material is loaded, and after degreasing, pickling, ultrasonic deashing, galvanizing and polishing, the galvanized NdFeB material is obtained. In the environmentally friendly passivation process, the galvanized NdFeB material is placed in the passivation solution, passivated at room temperature for 5 seconds, and then the material is discharged and blown dry to obtain the NdFeB material of this embodiment.

[0079] Example 3

[0080] The formula of passivation solution is:

[0081] Chromium nitrate nonahydrate, 6g / L

[0082] Ammonium fluoride, 1g / L

[0083] Cobalt nitrate, 5g / L

[0084] Sodium nitrate, 3g / L

[0085] Malonic acid, 1.5 g / L

[0086] Glacial acetic acid, 3g / L

[0087] Water, 980ml / L

[0088] The pH value of the passivation solution is 1.8.

[0089] The preparation method of the passivation solution in the embodiment includes: first adding part of the water to the container, weighing chromium nitrate nonahydrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and glacial acetic acid according to the above formula, adding them to the water in sequence, and stirring until they are completely dissolved in the water; adding the remaining water and continuing to stir for 2 hours.

[0090] The passivation solution of this embodiment is used in the environmentally friendly passivation process of the NdFeB process production line. Figure 1 As shown, specifically: first, the NdFeB raw material is loaded, and after degreasing, pickling, ultrasonic deashing, galvanizing and polishing, the galvanized NdFeB material is obtained. In the environmentally friendly passivation process, the galvanized NdFeB material is placed in the passivation solution, passivated at room temperature for 8s, and then the material is discharged and blown dry to obtain the NdFeB material of this embodiment.

[0091] Comparative Example 1

[0092] The formula of passivation solution is:

[0093] Chromium nitrate nonahydrate, 3g / L;

[0094] Ammonium fluoride, 1 g / L;

[0095] Cobalt nitrate, 3 g / L;

[0096] Sodium nitrate, 2 g / L;

[0097] Malonic acid, 1.5 g / L;

[0098] Glacial acetic acid, 2 g / L;

[0099] Water, 985ml / L;

[0100] Surfactant, 0.01~0.1g / L.

[0101] The pH value of the passivation solution is 2.0.

[0102] The preparation method of the passivation solution in the embodiment includes: first adding part of the water to the container, weighing chromium nitrate nonahydrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid, glacial acetic acid and surfactant according to the above formula, adding them to the water in sequence, and stirring until they are completely dissolved in the water; adding the remaining water and continuing to stir for 2 hours.

[0103] The passivation solution of this embodiment is used in the environmentally friendly passivation process of the NdFeB process production line. Figure 1 As shown, specifically: first, the NdFeB raw material is loaded, and after degreasing, pickling, ultrasonic deashing, galvanizing and polishing, the galvanized NdFeB material is obtained. In the environmentally friendly passivation process, the galvanized NdFeB material is placed in the passivation solution, passivated at room temperature for 8s, and then the material is discharged and blown dry to obtain the NdFeB material of this embodiment.

[0104] Effect Example 1

[0105] According to GB / T 228.1-2010, the passivated NdFeB magnets from Examples 1-3 and Comparative Example 1 were bonded to a rotor. The rotor was fixed in position and the shear force of the coatings was tested using an electronic universal testing machine with a side push at a test speed of 0.5 nm / min. The test results for Examples 1-3 and Comparative Example 1 are shown in Table 1 below.

[0106] Table 1

[0107]

[0108]

[0109] Note: / indicates untested

[0110] Comparative Example 1 adds a surfactant on the basis of Example 1. Compared with Example 1, the tensile strength of Comparative Example 1 is reduced from 29.1763 MPa to 15.1254 MPa, indicating that the addition of the surfactant is not conducive to the adhesiveness of the NdFeB surface.

[0111] Effect Example 2

[0112] The galvanized NdFeB material obtained before the environmental passivation process in Example 1 and the NdFeB material obtained after the blanking and drying step were respectively taken. The adhesive affinity of the two materials was tested using an electronic universal testing machine according to GB / T 228.1-2010. The results are shown in the attached manual. Figure 2 .

[0113] Depend on Figure 2 It can be seen that after the surface of NdFeB is passivated by the passivating agent of the present invention, its adhesiveness is greatly improved compared with that before passivation.

Claims

1. A passivating agent for zinc-plated NdFeB material, characterized in that: By mass, it consists of the following components: Chromium nitrate, 3-10 parts; Ammonium fluoride, 1-5 parts; Cobalt nitrate, 3-8 parts; Sodium nitrate, 2-5 parts; Malonic acid, 0.5-2 parts; Acetic acid, 1-5 parts; The passivating agent does not contain a surfactant; The mass ratio of the ammonium fluoride to chromium nitrate is 1:(4-6).

2. The passivating agent for zinc-plated NdFeB material according to claim 1, wherein The chromium nitrate is chromium nitrate nonahydrate; And / or, the acetic acid is glacial acetic acid; And / or, the amount of chromium nitrate is 4 to 9 parts; And / or, the amount of ammonium fluoride is 2 to 4 parts; And / or, the amount of cobalt nitrate is 3 to 6 parts; And / or, the amount of sodium nitrate is 2 parts or 3 parts; And / or, the amount of malonic acid is 1.5 parts; and / or, the amount of acetic acid is 1.5 parts, 2 parts or 3 parts; And / or, the mass ratio of the sodium nitrate, cobalt nitrate and chromium nitrate is 1:(0.7-3):(0.7-4); and / or, the mass ratio of malonic acid to acetic acid is 1:(1-9); And / or, the mass ratio of ammonium fluoride to malonic acid is 1:(0.5~1.8).

3. The passivating agent for zinc-plated NdFeB material according to claim 2, wherein: The amount of chromium nitrate is 5 to 8 parts; And / or, the amount of cobalt nitrate is 5 parts; And / or, the mass ratio of the sodium nitrate, cobalt nitrate and chromium nitrate is 1:(1-2):(1-3); And / or, the mass ratio of malonic acid to acetic acid is 1:(2-7); And / or, the mass ratio of ammonium fluoride to malonic acid is 1:(1-1.6).

4. The passivating agent for zinc-plated NdFeB material according to claim 2, wherein: The amount of chromium nitrate is 6 parts; And / or, the mass ratio of sodium nitrate, cobalt nitrate and chromium nitrate is 1:1.5:1.5; And / or, the mass ratio of malonic acid to acetic acid is 1:3; And / or, the mass ratio of ammonium fluoride to malonic acid is 1:1.

5.

5. The passivating agent for zinc-plated NdFeB material according to claim 1, wherein The mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 3:1:3:2:1.5:2; Alternatively, the mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 4:1:2:3:0.5:1.5; Alternatively, the mass ratio of the chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid is 6:1:5:3:1.5:

3.

6. A passivation solution for zinc-plated NdFeB material, characterized in that: The invention comprises the passivating agent for zinc-plated NdFeB material according to any one of claims 1 to 5 and water; the pH value of the passivating solution is 1.8 to 2.

2.

7. The passivation solution for zinc-plated NdFeB material according to claim 6, wherein: The pH value of the passivation solution is 2.

0.

8. The passivation solution for plating zinc NdFeB material according to claim 6, wherein: The concentration of the passivation solution is 10-20 g / L.

9. The passivation solution for zinc-plated NdFeB material according to claim 8, wherein: The concentration of the passivation solution is 12.5 g / L or 19.5 g / L.

10. A method for preparing a passivation solution for zinc-plated NdFeB material according to any one of claims 6 to 9, characterized in that: It includes the following steps: The passivating agent is dissolved in water to obtain the product.

11. The method for preparing a passivation solution for zinc-plated NdFeB material according to claim 10, wherein: The preparation method of the passivation solution comprises: firstly dissolving the passivating agent in part of water, and then adding the remaining water.

12. The method for preparing a passivation solution for zinc-plated NdFeB material according to claim 11, wherein: The preparation method of the passivation solution comprises: firstly dissolving chromium nitrate, ammonium fluoride, cobalt nitrate, sodium nitrate, malonic acid and acetic acid in part of water in sequence, and then adding the remaining water.

13. A passivation film for zinc-plated NdFeB material, characterized in that: The passivation solution for zinc-plated NdFeB material is used to passivate the surface of the zinc-plated NdFeB material.

14. A neodymium iron boron material, characterized in that: It comprises the passivation film for plating zinc neodymium iron boron material as claimed in claim 13.

15. Use of the passivating agent for zinc-plated NdFeB material according to any one of claims 1 to 5 or the passivating solution for zinc-plated NdFeB material according to any one of claims 6 to 9 in the environmentally friendly passivation process of a NdFeB production line.

16. The use according to claim 15, characterized in that The environmentally friendly passivation time is 5 to 10 seconds.

17. The use according to claim 16, characterized in that The environmentally friendly passivation time is 5 seconds or 8 seconds.

18. The use according to claim 15, characterized in that In the NdFeB process production line, the environmentally friendly passivation process step is after the light output process step.

19. The use according to claim 18, characterized in that The process step of galvanizing is also included before the process step of emitting light.

20. A neodymium iron boron process production line, characterized in that: The environmentally friendly passivation process uses the passivator for zinc-plated NdFeB materials according to any one of claims 1 to 5 or the passivation solution for zinc-plated NdFeB materials according to any one of claims 6 to 9.

21. The NdFeB process production line according to claim 20, characterized in that: The NdFeB process production line includes the following process flow: loading → degreasing → pickling → ultrasonic deashing → galvanizing → polishing → environmentally friendly passivation → unloading and drying.

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