Phosphorus-free passivation solution composition, preparation method thereof and magnetic steel surface treatment method

Abstract

The invention belongs to the technical field of metal surface treatment, and particularly relates to a phosphorus-free passivation solution composition, a preparation method thereof and a magnetic steel surface treatment method.The phosphorus-free passivation solution composition comprises a first passivation solution and a second passivation solution; the passivation solution I comprises the following components in percentage by mass: 4-7% of a silane coupling agent; 3%-6% of ammonium molybdate; 4%-6% of a fatty alcohol nonionic surfactant; 1%-3% of amino acid; 6%-8% of citric acid; and the balance of deionized water. The passivation solution II comprises the following components in percentage by mass: 4-7% of a silane coupling agent; 3%-6% of ammonium molybdate; 2%-4% of nano silicon dioxide particles; 1%-3% of amino acid; 6%-8% of citric acid; 2%-4% of cerous nitrate; and the balance of deionized water. The problem of eutrophication of a water body caused by a traditional phosphating solution is solved, and the problems that a non-phosphorus passivation film is not uniform, the adhesive force is poor, and the salt spray resistance is insufficient are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a phosphorus-free passivation solution composition, a preparation method thereof and a magnetic steel surface treatment method, and belongs to the technical field of metal surface treatment. BACKGROUND

[0002] Neodymium iron boron magnetic steel, as an important permanent magnet material, is widely used in electronic, electrical, mechanical and other fields. However, due to the easy oxidation and corrosion of neodymium iron boron magnetic steel, its service life and performance are affected. In order to improve the corrosion resistance of neodymium iron boron magnetic steel, it is necessary to carry out passivation treatment on its surface. At present, the commonly used passivation process in industry mainly includes two ways of chromium-containing passivation and phosphorus-containing passivation.

[0003] With the increasingly strict environmental protection requirements, the traditional chromium-containing passivation process has been gradually eliminated due to its high toxicity, serious environmental pollution and other problems.

[0004] The preparation method of a passivation solution and a blue-white passivation film disclosed in Chinese patent application with publication number CN114107969A points out that the hexavalent chromium salt passivation technology has the defects of high toxicity and environmental pollution, and a more environmentally friendly passivation technology needs to be developed. Although the phosphorus-containing passivation process solves the environmental protection problem of chromium-containing passivation to some extent, the introduction of phosphorus element also leads to water eutrophication, which does not meet the increasingly strict environmental protection requirements. In addition, the existing phosphorus-free passivation solution has the problems of uneven film formation, poor adhesion, insufficient wet heat resistance and the like, and it is difficult to meet the high corrosion resistance requirements of neodymium iron boron magnetic steel.

[0005] Chinese patent application with publication number CN105803435A discloses an environmentally friendly full-chromium-free passivation process for steel flywheels. The process uses a resin-based full-chromium-free passivation solution, which can obtain a full-chromium-free passivation film with strong adhesion on the surface of the steel flywheel, and the passivation film has high corrosion resistance. However, the process needs to go through multiple steps such as complex surface pickling, water rinsing, immersion in passivation solution and drying forming, and the process flow is complex, and the production efficiency is low.

[0006] Chinese patent application with publication number CN104233261A discloses a chromium-free and phosphorus-free passivation solution for steel surface, which composition includes silane compounds, water-based unsaturated polyester, N,N-dimethyl aniline and the like. Chinese patent application with publication number CN104233264A discloses the preparation process of the passivation solution. Although these chromium-free and phosphorus-free passivation solutions have improved in environmental protection, their formulations are complex, the cost is high, and the applicability and corrosion resistance of neodymium iron boron magnetic steel have not been fully verified.

[0007] A Chinese patent application with the publication number CN107937893A discloses an environmentally-friendly passivation solution for aluminum or aluminum alloy, and a preparation method and a treatment process thereof. The passivation solution includes a main film-forming agent, a secondary film-forming agent, a strong oxidizing hole-filling agent, and other components. Although the passivation solution has high stability, uniform and dense passivation film, and high corrosion resistance, it is mainly designed for aluminum or aluminum alloy, and has limited applicability for neodymium-iron-boron magnetic steel.

[0008] In summary, the passivation of neodymium-iron-boron magnetic steel in the prior art has the following problems: first, the traditional passivation process uses a phosphorus-containing passivation solution, which introduces phosphorus elements that can easily lead to water eutrophication, which does not meet environmental protection requirements; second, some phosphorus-free passivation solutions have the problems of uneven film formation, poor adhesion, insufficient wet heat resistance, etc.; third, the traditional passivation process is complex and requires pre-plating and post-plating treatment; fourth, the prior art has not yet provided a low-cost and environmentally-friendly passivation solution and an efficient phosphorus-free passivation method that can simultaneously meet the high corrosion resistance of the passivation film of neodymium-iron-boron magnetic steel and the industrial production requirements.

[0009] Therefore, it is urgent to develop an environmentally-friendly phosphorus-free passivation film and a passivation process to solve the above technical problems. SUMMARY

[0010] The present application provides a phosphorus-free passivation solution composition, a preparation method thereof, and a magnetic steel surface treatment method to solve the above technical problems.

[0011] The technical solution of the present application to solve the above technical problems is as follows: One of the objects of the present application is to provide a phosphorus-free passivation solution composition, which includes passivation solution one and passivation solution two. The passivation solution one includes, in mass percentage: Silane coupling agent 4% to 7%; Ammonium molybdate 3% to 6%; Fatty alcohol non-ionic surfactant 4% to 6%; Amino acid 1% to 3%; Citric acid 6% to 8%; The balance is deionized water. The passivation solution two includes, in mass percentage: Silane coupling agent 4% to 7%; Ammonium molybdate 3% to 6%; Nano-silicon dioxide particles 2% to 4%; Amino acid 1% to 3%; Citric acid 6% to 8%; Cerium nitrate 2% to 4%; The balance is deionized water.

[0012] The beneficial effects of the present application are that: the present application forms a passivation film by the synergistic film-forming effect of silane coupling agent and rare earth salt and molybdate, the passivation film formed by the passivation liquid composition of the present application does not contain phosphorus element, avoids the water eutrophication problem caused by traditional phosphating liquid, and meets the international environmental protection standard; meanwhile, heating is not needed in the process of passivation, energy is saved, and remarkable environmental protection benefits are obtained, the problems of uneven passivation film, poor adhesion, insufficient salt mist resistance and the like of non-phosphorus passivation are solved, and the passivation film formed by the passivation liquid composition of the present application on the surface of a magnetic steel can withstand more than 2 hours in a humidity 85%, temperature 85℃ wet heat test.

[0013] On the basis of the above technical solution, the present application can also be improved as follows: Further, the length of the fatty chain of the silane coupling agent in the passivation liquid one is C8-C18.

[0014] Further, the length of the fatty chain of the silane coupling agent in the passivation liquid two is C8-C18.

[0015] Further, the particle size of the nano-silicon dioxide particles in the passivation liquid two is 50nm-100nm.

[0016] Further, the fatty alcohol non-ionic surfactant is a polyoxyethylene ether with a carbon chain length of C8-C10.

[0017] Further, the amino acid in the passivation liquid one is lysine.

[0018] Further, the amino acid in the passivation liquid two is lysine.

[0019] The second purpose of the present application is to provide a preparation method of the above-mentioned non-phosphorus passivation liquid composition, which respectively comprises preparation of the passivation liquid one and preparation of the passivation liquid two.

[0020] Further, the preparation of the passivation liquid one comprises the following steps: S11, at room temperature, the silane coupling agent, amino acid, citric acid and deionized water are mixed until completely dissolved, the pH is adjusted to 4-5, and hydrolysis is performed for 30min-60min; S12, the ammonium molybdate and the fatty alcohol non-ionic surfactant are sequentially added and stirred until completely dissolved; after quantitative configuration, standing and aging is performed for more than 24 hours.

[0021] Further, the preparation of the passivation liquid two comprises the following steps: S21, at room temperature, the silane coupling agent, amino acid, citric acid and deionized water are mixed until completely dissolved, the pH is adjusted to 5-6, and hydrolysis is performed for 30min-60min; S22, sequentially add ammonium molybdate, cerium nitrate, nano-silicon dioxide particles, and stir until completely dissolved; after quantitative configuration, stand for aging for 24 hours or more.

[0022] A third object of the present application is to provide a magnetic steel surface treatment method using the above-mentioned non-phosphorus passivation solution composition; specifically comprising the following steps: I. Feeding; II. Brushing: using a rotating nylon brush, the bristles are sprayed with passivation solution I, the surface of the magnetic steel is brushed, the temperature is 20-30 DEG C, and the time is 4 min / single side-6 min / single side; III. Ultrasonic water washing: deionized water ultrasonic water washing of magnetic steel, time is 1-3 min; IV. Immersion: the magnetic steel is immersed in passivation solution II, the temperature is 20-30 DEG C, and the time is 4-6 min; V. Drying: the magnetic steel is placed in an oven, 90-120 DEG C, 8-12 min, drying.

[0023] The surface treatment process of the present application significantly simplifies the surface treatment process of neodymium iron boron magnetic steel, by using passivation solution I to directly brush the surface of the magnetic steel after feeding, the traditional process of alkaline degreasing, pickling, surface conditioning and other pretreatment processes are omitted; by immersing the magnetic steel in the passivation solution II containing nano-silicon dioxide particles, the post-treatment process such as water washing and spraying is omitted, making the whole process more suitable for continuous production, greatly improving the production efficiency. The present application simplifies the pretreatment and post-treatment processes before and after passivation, reduces the process steps and equipment investment, reduces the production cost, at the same time improves the production efficiency, has good economic effect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The electron microscope detection results of the product of example 1; Figure 2 The electron microscope detection results of the product of example 2; Figure 3 The electron microscope detection results of the product of example 3; Figure 4 The electron microscope detection results of the product of example 4; Figure 5 The electron microscope detection results of the product of example 5; Figure 6 The electron microscope detection results of the product of example 6; Figure 7 The electron microscope detection results of the product of comparative example 1; Figure 8 The electron microscope detection results of the product of comparative example 2. DETAILED DESCRIPTION

[0025] The principles and features of the present application are described below in conjunction with the accompanying drawings, which are only used to explain the present application and not intended to limit the scope of the present application.

[0026] Example 1 Square Nd-Fe-B magnetic steel with specifications of 14mm x 7mm x 1mm is selected.

[0027] Passivation solution one is configured as follows: (1) At room temperature, 7% of dodecyltrimethoxysilane, 3% of lysine and 70% of deionized water, 8% of citric acid are mixed until completely dissolved, the pH is adjusted to 4-5, and hydrolysis is performed for 60 minutes; (2) 6% of ammonium molybdate and 6% of decyl polyoxyethylene ether are sequentially added, stirred until completely dissolved, and quantitatively configured to 100 Kg for standing and aging for 24 hours.

[0028] Passivation solution two is configured as follows: (1) At room temperature, 7% of dodecyltrimethoxysilane, 3% of lysine and 68% of deionized water, 8% of citric acid are mixed until completely dissolved, the pH is adjusted to 5-6, and hydrolysis is performed for 60 minutes; (2) 6% of ammonium molybdate, 4% of cerium nitrate and 4% of silica nanoparticles with an average particle size of 80-100 nm are sequentially added, stirred until completely dissolved, and quantitatively configured to 100 Kg for standing and aging for 24 hours.

[0029] The surface passivation treatment of the Nd-Fe-B magnetic steel is performed according to the following specific steps: (1) Feeding: 1200 pieces of square Nd-Fe-B magnetic steel are placed in a conveying tool, which is a stainless steel mesh container in this embodiment; (2) Brushing: At room temperature, a rotary nylon brush with a brush density ≥2000 roots / m 2 and a linear speed controlled at 1.5m / s-2.5m / s is used, and the linear speed is controlled at 2.0m / s in this embodiment, and the surface of the brush is sprayed with passivation solution one, and then the surface of the magnetic steel is brushed in the tool for 6 minutes per side; (3) Ultrasonic water washing: The magnetic steel is ultrasonically washed with deionized water at 28 kHz and 5A for 2 minutes; (4) Immersion: The magnetic steel is immersed in passivation solution two at room temperature for passivation, and the immersion time is 5 minutes; (5) Drying: The magnetic steel is placed in an oven at 100°C for 10 minutes for drying.

[0030] The magnetic steel of this embodiment is scanned by an electron microscope using a high-speed electron beam instead of visible light imaging, and the electron microscope test results are shown in Figure 1 .

[0031] Example 2 Square Nd-Fe-B magnetic steel with specifications of 14mm x 7mm x 1mm is selected.

[0032] Passivation solution one is configured as follows: (1) At room temperature, 6% of dodecyltrimethoxysilane, 2% of lysine and 73% of deionized water, 7% of citric acid are mixed until completely dissolved, the pH is adjusted to 4-5, and hydrolysis is performed for 45 min; (2) 6% of ammonium molybdate and 6% of decyl polyoxyethylene ether are sequentially added, stirred until completely dissolved, and quantitatively configured to 100 Kg and left to stand for 24 hours.

[0033] Passivation solution two is configured as follows: (1) At room temperature, 6% of dodecyltrimethoxysilane, 2% of lysine and 71% of deionized water, 7% of citric acid are mixed until completely dissolved, the pH is adjusted to 5-6, and hydrolysis is performed for 45 min; (2) 6% of ammonium molybdate, 4% of cerium nitrate and 4% of silica nanoparticles with an average particle size of 60-80 nm are sequentially added, stirred until completely dissolved, and quantitatively configured to 100 Kg and left to stand for 24 hours.

[0034] The Nd-Fe-B magnetic steel is subjected to surface passivation treatment, and the specific steps are as follows: (1) Feeding: 1200 pieces of square Nd-Fe-B magnetic steel are placed in a conveying stainless steel mesh container; (2) Brushing: At room temperature, a rotating nylon brush with a brush density of ≥2000 roots / m 2 and a linear speed controlled at 1.5 m / s-2.5 m / s is used to brush the surface of the magnetic steel, and the linear speed is controlled at 2.0 m / s in this embodiment. The brush surface is sprayed with passivation solution one, and then the surface of the magnetic steel is brushed in the tool for 5 min per side; (3) Ultrasonic water washing: The magnetic steel is subjected to ultrasonic water washing with deionized water at 28 kHz and 5 A for 2 min; (4) Immersion: The magnetic steel is immersed in passivation solution two at room temperature for 5 min; (5) Drying: The magnetic steel is placed in an oven at 100°C for 10 min for drying.

[0035] The magnetic steel of this embodiment is subjected to electron microscope imaging scanning of the surface by using a high-speed electron beam instead of visible light, and the electron microscope test results are shown in Figure 2 It can be seen from the figure that the surface of the product is flat and has no obvious pores, indicating that the magnetic steel obtained by using the passivation solution composition and the surface passivation treatment process of this embodiment has a uniform film on the surface and no obvious pores.

[0036] Example 3 Square Nd-Fe-B magnetic steel with specifications of 14mm x 7mm x 1mm is selected.

[0037] Passivation solution one: (1) At room temperature, mix dodecyltrimethoxysilane 4%, lysine 1% with deionized water 77%, citric acid 6% to complete dissolution, adjust pH to 4-5, hydrolyze for 30 min; (2) Add ammonium molybdate 6%, decyl polyoxyethylene ether 6% in turn, stir to complete dissolution, and then quantitatively configure to 100 Kg and stand for aging for 24 hours.

[0038] Passivation solution two: (1) At room temperature, mix dodecyltrimethoxysilane 4%, lysine 1% with deionized water 75%, citric acid 6% to complete dissolution, adjust pH to 5-6, hydrolyze for 30 min; (2) Add ammonium molybdate 6%, cerium nitrate 4%, and silica nanoparticles with an average particle size of 50-60 nm 4% in turn, stir to complete dissolution; quantitatively configure to 100 Kg and stand for aging for 24 hours.

[0039] The surface passivation treatment of the neodymium-iron-boron magnetic steel includes the following specific steps (1) Feeding: 1200 pieces of square neodymium-iron-boron magnetic steel are placed in a conveying tool; (2) Brushing: At room temperature, a rotating nylon brush with a brush density of ≥2000 roots / m 2 and a linear speed controlled at 1.5 m / s-2.5 m / s is used to brush the surface of the magnetic steel, and the linear speed is controlled at 2.0 m / s in this embodiment. The surface of the brush is sprayed with passivation solution one, and then the surface of the magnetic steel is brushed in the tool for 4 min per side; (3) Ultrasonic water washing: The magnetic steel is ultrasonically washed with deionized water at 28 kHz and 5 A for 2 min; (4) Immersion: At room temperature, the magnetic steel is immersed in passivation solution two for passivation, and the immersion time is 5 min; (5) Drying: The magnetic steel is placed in an oven at 100°C for 10 min for drying.

[0040] The electron microscope test results obtained by using a high-speed electron beam to replace visible light to image and scan the surface of the magnetic steel of this embodiment are shown in Figure 3 It can be seen from the figure that the surface of the product is basically flat but has pores, indicating that the magnetic steel obtained by using the passivation solution composition and the surface passivation treatment process of this embodiment has a relatively uniform film formation.

[0041] Example 4 Square neodymium-iron-boron magnetic steel with a specification of 14 mm x 7 mm x 1 mm is selected.

[0042] Passivation solution one: (1) At room temperature, mix 6% dodecyltrimethoxysilane, 2% lysine, 73% deionized water, and 7% citric acid until completely dissolved, adjust the pH to 4-5, and hydrolyze for 45 minutes; (2) Add 6% ammonium molybdate and 6% decyl polyoxyethylene ether in sequence, stir until completely dissolved, and prepare to 100 kg, then let it stand and age for 24 hours.

[0043] Configure passivation solution 2: (1) At room temperature, mix 6% dodecyltrimethoxysilane, 2% lysine, 71% deionized water, and 7% citric acid until completely dissolved, adjust the pH to 5-6, and hydrolyze for 45 minutes; (2) Add 6% ammonium molybdate, 4% cerium nitrate, and 4% silicon dioxide nanoparticles with an average particle size of 60-80 nm in sequence, and stir until completely dissolved; after quantitatively preparing to 100 kg, let it stand and age for 24 hours.

[0044] The surface passivation treatment of NdFeB magnets is as follows: (1) Loading: Place 1200 square NdFeB magnets into the conveyor tooling; (2) Brushing: At room temperature, use a rotating nylon brush with a bristle density of ≥ 2000 pieces / m 2 , the linear speed is controlled at 1.5m / s~2.5m / s. In this embodiment, the linear speed is controlled at 1.5m / s. The passivation liquid 1 is sprayed on the surface of the brush, and then the surface of the magnetic steel is brushed in the tooling for 5min / single side; (3) Ultrasonic washing: Use deionized water to ultrasonically wash the magnetic steel, 28kHz, 4A, time for 2min; (4) Immersion: Immerse the magnetic steel in the passivation solution 2 at room temperature for 5 minutes; (5) Drying: Place the magnet in an oven at 100°C for 10 minutes and dry it.

[0045] The magnetic steel of this embodiment is tested by electron microscope using high-speed electron beam instead of visible light to scan the surface. Figure 4 .from Figure 4 The results show that the surface of the product is basically flat but has pores, indicating that the magnetic steel surface film obtained by adopting the passivation liquid composition and surface passivation treatment process of this embodiment is relatively uniform. However, due to the low speed of the brush, impurities may remain on the surface before passivation, resulting in a decrease in the surface flatness of the product compared with other embodiments.

[0046] Example 5 Select square NdFeB magnets with specifications of 14mm×7mm×1mm.

[0047] Prepare passivation solution 1: (1) At room temperature, mix dodecyltrimethoxysilane 6%, lysine 2% with deionized water 73%, citric acid 7% to complete dissolution, adjust pH to 4-5, hydrolyze for 45 min; (2) Add ammonium molybdate 6%, decyl polyoxyethylene ether 6% in turn, stir to complete dissolution, and then quantitatively configure to 100 Kg and stand for aging for 24 hours.

[0048] Prepare passivation solution two: (1) At room temperature, mix dodecyltrimethoxysilane 6%, lysine 2% with deionized water 71%, citric acid 7% to complete dissolution, adjust pH to 5-6, hydrolyze for 45 min; (2) Add ammonium molybdate 6%, cerium nitrate 4%, and silica nanoparticles with an average particle size of 60-80 nm 4% in turn, stir to complete dissolution; then quantitatively configure to 100 Kg and stand for aging for 24 hours.

[0049] The specific steps for the surface passivation treatment of the neodymium-iron-boron magnetic steel are as follows (1) Feeding: Place 1200 square neodymium-iron-boron magnetic steels in the conveying tool; (2) Brushing: At room temperature, use a rotating nylon brush with a brush density of ≥2000 roots / m 2 , control the linear speed at 2.5 m / s, spray the passivation solution one on the surface of the brush, and then brush the surface of the magnetic steel in the tool for 5 min per side; (3) Ultrasonic water washing: Use deionized water to ultrasonically wash the magnetic steel at 28 kHz and 6 A for 2 min; (4) Immersion: Immers the magnetic steel in the passivation solution two for passivation, at a temperature of 30°C for 5 min; (5) Drying: Place the magnetic steel in an oven at 100°C for 10 min for drying.

[0050] The electron microscope test results obtained by using a high-speed electron beam to replace visible light to image and scan the surface of the magnetic steel of the present embodiment are shown in Figure 5 It can be seen from the figure that the surface of the product is basically flat but has pores, indicating that the magnetic steel obtained by using the passivation liquid composition and the surface passivation treatment process of the present embodiment has a relatively uniform film formation.

[0051] Example 6 Square neodymium-iron-boron magnetic steels with a specification of 14 mm x 7 mm x 1 mm are selected.

[0052] Prepare passivation solution one: (1) At room temperature, mix dodecyltrimethoxysilane 6%, lysine 2% with deionized water 73%, citric acid 7% to complete dissolution, adjust pH to 4-5, hydrolyze for 45 min; (2) Add ammonium molybdate 6%, decyl polyoxyethylene ether 6% successively, stir until completely dissolved, and then configure to 100 Kg and stand for aging for 24 hours after quantification.

[0053] Configuration of passivation solution two: (1) At room temperature, mix dodecyl triethoxysilane 6%, lysine 2% with deionized water 71%, citric acid 7% until completely dissolved, adjust pH to 5-6, and hydrolyze for 45 min; (2) Add ammonium molybdate 6%, cerium nitrate 4%, and silica nanoparticles with an average particle size of 60-80 nm 4% successively, stir until completely dissolved; configure to 100 Kg after quantification, and stand for aging for 24 hours.

[0054] The specific steps of the surface passivation treatment of the neodymium-iron-boron magnetic steel are as follows: (1) Feeding: 1200 pieces of square neodymium-iron-boron magnetic steel are placed in a stainless steel mesh container; (2) Brushing: At room temperature, a rotating nylon brush with a brush density of ≥2000 roots / m 2 and a linear speed controlled at 2.0 m / s is used to spray passivation solution one on the surface of the brush, and then the magnetic steel surface is brushed in the tooling for 5 min per side; (3) Ultrasonic water washing: The magnetic steel is ultrasonically washed with deionized water at 28 kHz and 5 A for 2 min; (4) Immersion: The magnetic steel is immersed in passivation solution two at room temperature for passivation, and the immersion time is 5 min; (5) Drying: The magnetic steel is placed in an oven at 100°C for 10 min for drying.

[0055] The electron microscope test results obtained by using a high-speed electron beam to replace visible light to image and scan the surface of the magnetic steel of the example are shown in Figure 6 It can be seen from the figure that the surface of the product is basically flat but has pores, indicating that the passivation solution and the passivation treatment process of the comparative example have poor film forming effect on the surface of the magnetic steel.

[0056] Comparative Example 1 Square neodymium-iron-boron magnetic steel with a specification of 14 mm x 7 mm x 1 mm is selected.

[0057] Hankou Bonderite 958 is diluted with pure water according to a ratio of 1:1 and 1:99 respectively, and a phosphating solution with a concentration of 50% and a surface conditioning solution with a concentration of 1% are prepared for standby.

[0058] The specific steps of the surface passivation treatment of the neodymium-iron-boron magnetic steel are as follows: (1) Feeding: 1200 pieces of square neodymium-iron-boron magnetic steel are placed in a stainless steel mesh container; (2) Ultrasonic degreasing: immerse the magnetic steel in 5% NaC03 solution, 28 kHz, 6A, ultrasonic for 4 min; (3) Ultrasonic water washing: wash the magnetic steel with water, 28 kHz, 6A, ultrasonic for 4 min; (4) Immersion in surface conditioning liquid: immerse the magnetic steel in the surface conditioning liquid at room temperature for 5 min to complete the pretreatment; (5) Immersion in phosphating liquid: immerse the magnetic steel in the phosphating liquid at room temperature for 5 min to complete the passivation treatment; (6) Ultrasonic water washing: wash the magnetic steel with water, 28 kHz, 6A, ultrasonic for 4 min; (7) Blow drying: 90°C for 5 min; (8) Drying: place the magnetic steel in an oven at 100°C for 10 min to dry.

[0059] The electron microscope test results of the magnetic steel of the present comparative example are shown in Figure 7 It can be seen from the figure that the surface of the product is relatively flat but has pores, indicating that the surface film forming effect of the magnetic steel obtained by using the passivation liquid and the passivation treatment process of the present comparative example is poor.

[0060] Comparative Example 2 Select square Nd-Fe-B magnetic steel with specifications of 14 mm x 7 mm x 1 mm, Dilute Hengao Bonderite 958 with pure water according to a ratio of 1:1 and 1:99 respectively, prepare a phosphating liquid with a concentration of 50% and a surface conditioning liquid with a concentration of 1% for standby.

[0061] The passivation treatment of the surface of the Nd-Fe-B magnetic steel includes the following specific steps: (1) Feeding: place 1200 pieces of square Nd-Fe-B magnetic steel in a conveying stainless steel mesh container; (2) Brushing: at room temperature, use a rotating nylon brush with a brush density of ≥2000 roots / m 2 , control the linear speed at 2 m / s, spray the surface conditioning liquid on the surface of the brush, and then brush the surface of the magnetic steel in the tool for 5 min per side; (3) Ultrasonic water washing: ultrasonic water washing of the magnetic steel with deionized water, 28 kHz, 5A, for 2 min; (4) Immersion: immerse the magnetic steel in the phosphating liquid at room temperature for 5 min for passivation; (5) Drying: place the magnetic steel in an oven at 100°C for 10 min to dry.

[0062] The electron microscope test results of the magnetic steel of the present example, which is scanned by an electron microscope using a high-speed electron beam instead of visible light, are shown in Figure 8As can be seen in the figure, the surface of the product is relatively flat but has pores, which indicates that the film-forming effect on the surface of the magnetic steel obtained by adopting the passivation solution and passivation treatment process of this comparative example is poor.

[0063] The magnetic steels of the embodiment and the comparative example were subjected to a wet heat test.

[0064] The test conditions of the damp heat experiment in the present invention are: placing the magnetic steel in a closed environment with a temperature of 85° C. and a humidity of 85%, and observing the rust of the coating.

[0065] The test conditions of the salt spray test in the present invention are as follows: placing the magnetic steel in an artificial salt spray atmosphere with a temperature of 35±2°C and a sodium chloride solution of 5±0.5%, and observing the rust of the coating.

[0066] The test conditions of the shear test in the present invention are as follows: the magnetic steel is placed in the shear fixture by gluing, and then an electronic universal testing machine is used to apply a load at a uniform speed until the fixture and the magnetic steel are relatively displaced.

[0067] The results of the above tests are shown in Table 1, where: The wet heat time and salt spray time in Table 1 are the times when the coating begins to rust.

[0068] The shear strength in Table 1 is the strength when the tooling and the magnetic steel parts undergo relative displacement.

[0069] Table 1 Results of wet heat test, salt spray test and shear test

[0070] From the results in Table 1 above, it can be seen that the magnetic steels of Examples 1-6 obtained by adopting the passivation liquid composition of the present invention and the surface passivation treatment process of the present invention have better corrosion resistance, and can remain rust-free for more than 2 hours under the conditions of a temperature of 85°C and a humidity of 85%, and can remain rust-free for more than 1 hour under a temperature of 35±2°C and a salt spray atmosphere of 5±0.5% sodium chloride solution, which is significantly better than Comparative Example 1.

[0071] From the results in Table 1 above, it can be seen that the magnetic steel obtained by adopting the passivation liquid composition of the present invention and the surface passivation treatment process of the present invention has good adhesion performance. The shear strength is measured. Except for Examples 1 and 4, which are close to Comparative Example 1, the other Examples are significantly better than Comparative Example 1. The shear strength of Example 2 can reach 28.67 MPa.

[0072] Depend on Figures 1-7 It can be seen that the magnetic steel surface obtained by adopting the passivation liquid composition and the surface passivation treatment process of the present invention has a uniform film without obvious pores, which is significantly better than the comparative example.

[0073] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A phosphorus-free passivation solution composition, characterized in that, Including passivation solution 1 and passivation solution 2; In terms of mass percentage, the first passivation solution comprises: Silane coupling agent 4% to 7%; Ammonium molybdate 3% to 6%; Fatty alcohol nonionic surfactants 4% to 6%; Amino acids 1% to 3%; Citric acid 6%-8%; The balance is deionized water; In terms of mass percentage, the second passivation solution comprises: Silane coupling agent 4% to 7%; Ammonium molybdate 3% to 6%; Nano-silicon dioxide particles 2% to 4%; Amino acids 1% to 3%; Citric acid 6%-8%; Cerium nitrate 2% to 4%; The balance was deionized water.

2. Phosphorus-free passivation solution composition according to claim 1, is characterized in that, In the passivation solution 1, the fatty chain length of the silane coupling agent is C8-C18; And / or, in the second passivation solution, the fatty chain length of the silane coupling agent is C8-C18.

3. Phosphorus-free passivation solution composition according to claim 1, is characterized in that, In the second passivation solution, the particle size of the nano-silicon dioxide particles is 50nm to 100nm.

4. Phosphorus-free passivation solution composition according to claim 1, characterized in that, The fatty alcohol nonionic surfactant is a polyoxyethylene ether with a carbon chain length of C8-C10.

5. Phosphorus-free passivation solution composition according to claim 1, characterized in that, In the passivation solution 1, the amino acid is lysine; And / or, in the second passivation solution, the amino acid is lysine.

6. A method for preparing the phosphorus-free passivation solution composition according to any one of claims 1 to 5, characterized in that: It includes the preparation of passivation solution 1 and the preparation of passivation solution 2 respectively.

7. The preparation method of the phosphorus-free passivating solution composition according to claim 6, wherein The preparation of the passivation solution 1 comprises the following steps: S11. At room temperature, mix the silane coupling agent, amino acid, citric acid and deionized water until completely dissolved, adjust the pH to 4-5, and hydrolyze for 30 min to 60 min; S12. Add ammonium molybdate and fatty alcohol nonionic surfactant in sequence, and stir until completely dissolved; after quantitative preparation, let it stand and age for more than 24 hours.

8. The preparation method of the phosphorus-free passivating solution composition according to claim 6, wherein The preparation of the passivation solution 2 comprises the following steps: S21. At room temperature, mix the silane coupling agent, amino acid, citric acid and deionized water until completely dissolved, adjust the pH to 5-6, and hydrolyze for 30 min to 60 min; S22. Add ammonium molybdate, cerium nitrate, and nano-silica particles in sequence, and stir until completely dissolved; after quantitative preparation, let stand and age for more than 24 hours.

9. A method for treating the surface of magnetic steel, characterized in that: The phosphorus-free passivation solution composition according to any one of claims 1 to 5 is used.

10. The magnetic steel surface treatment method according to claim 9, characterized in that: The following steps are involved:

1. Loading; 2. Brushing: Use a rotating nylon brush, spray the passivation liquid 1 on the bristle surface, and brush the surface of the magnetic steel at a temperature of 20℃~30℃, and the time is 4min / single side~6min / single side; 3. Ultrasonic water washing: ultrasonically wash the magnetic steel with deionized water for 1min to 3min; 4. Immersion: Immerse the magnetic steel in the passivation solution 2 at a temperature of 20℃~30℃ for 4min~6min; 5. Drying: Place the magnet in an oven at 90℃~120℃ for 8min~12min and dry it.

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