Green preparation method of silicon-containing FeCo-based nano-alloy surface composite passivation film

Abstract

The invention discloses a green preparation method of a silicon-containing FeCo-based nano-alloy surface composite passivation film, which comprises the steps of pretreatment, passivation solution preparation, dipping film formation and post-treatment strengthening, and the passivation solution is a silane-tannic acid composite passivation solution; according to the step of dipping and film forming, the pretreated alloy is dipped into a passivation solution, and a uniform primary film is formed; performing heat treatment and curing on the primary membrane to form a Si-O-M covalent network; and the post-treatment strengthening is that a potassium fluotitanate solution is adopted for sealing treatment, and micropores of the film layer are filled. Through molecular-level compounding of silane and TA, the passivation film with compactness, flexibility and a self-repairing function is constructed; meanwhile, nano cerium oxide is introduced as a nano filler and a corrosion inhibitor, so that the corrosion resistance is synergistically improved; and a low-temperature water-based process is used in the whole process, so that thermal damage to the nano-alloy is avoided, large-scale production can be realized, the limitation of a single-component passivation film is broken through, and an efficient and green solution is provided for anti-corrosion treatment of the high-activity nano-alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface treatment, and relates to a method for preparing an anti-corrosion passivation film for a silicon-containing FeCo-based nanometer alloy. Through the synergistic effect of a silane coupling agent and tannic acid, combined with the nano-material modification technology, a dense and corrosion-resistant composite passivation film is formed on the surface of the alloy, solving the pollution problem of the traditional chromate passivation process and the defect of insufficient performance of the existing chromium-free passivation film. Background Art

[0002] As a new type of soft magnetic material, the silicon-containing FeCo-based nanometer alloy is widely used in the fields of high-frequency transformers, magnetic shielding devices and aerospace sensors due to its high saturation magnetic induction intensity, low coercivity and excellent high-temperature resistance. However, during storage, due to its high surface activity, this alloy is easily eroded by water vapor, oxygen and acidic substances in the atmosphere, resulting in surface oxidation and corrosion. In particular, electrochemical microcells are easily formed at the interfaces between silicon-containing phases such as FeSi, CoSi and the FeCo matrix, accelerating the corrosion process and seriously affecting the service life and performance stability of the material. Therefore, it is necessary to perform anti-corrosion treatment on the surface. Currently, chromate passivation treatment is mainly used in industry to improve corrosion resistance. However, hexavalent chromium is highly toxic and carcinogenic and its use has been restricted. In recent years, chromium-free passivation technologies have become a research hotspot, such as silane passivation, phytic acid passivation and organic-inorganic composite passivation. Silane passivation forms a Si-O-Si network structure through the hydrolysis of a silane coupling agent, enhancing the adhesion of the film layer, but the single silane film layer has insufficient denseness and poor long-term corrosion resistance. Phytic acid (PA) is rich in hydroxyl and carboxyl groups and can form a stable metal-organic coordination structure by chelating metal ions, but the PA film layer has insufficient toughness and is prone to cracking under the action of stress. On the other hand, the synergistic effect of each component in the existing composite film layer has not been fully optimized.

[0003] Therefore, it is necessary to develop a new type of composite passivation process to solve the above problems, while also taking into account the environmental protection of the process and the controllability of the cost. Summary of the Invention

[0004] The main purpose of the present invention is to propose a green and efficient passivation process for the surface of a silicon-containing FeCo-based nanometer alloy to solve technical problems such as insufficient denseness and poor bonding force of the film layer in the existing process.

[0005] To achieve the above object, the present invention adopts the following design scheme: Green preparation method of silicon-containing FeCo-based nano-alloy surface composite passivation film, including pretreatment, passivation solution preparation, immersion film formation and post-treatment strengthening, wherein the passivation solution is a silane-tannic acid composite passivation solution; the immersion film formation is to immerse the pretreated alloy into the passivation solution to form a uniform primary film; the primary film is heat-treated and cured to promote the polycondensation of silane and the chelation reaction between TA and the metal surface, forming a Si-O-M covalent network, where M is Fe / Co; the post-treatment strengthening is to perform a sealing treatment with a potassium fluotitanate solution to fill the micropores of the film layer and improve the salt spray resistance performance.

[0006] The control temperature for forming the primary film is 25 - 40 °C, the immersion time is 5 - 10 min, and the pulling speed is 1 - 2 mm / s.

[0007] The pretreatment process includes ultrasonic alkali cleaning with a NaOH solution to remove surface oil stains and oxides and pickling activation with a mixed solution of dilute nitric acid and hydrogen peroxide to form a microscopically rough surface to enhance the film layer adhesion.

[0008] The preparation method of the silane-tannic acid composite passivation solution is as follows: a. Dissolve silane coupling agents KH560 (10 - 15 wt.%) and KH570 (5 - 8 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 4 - 5, and magnetically stir for 2 - 4 h to form a transparent hydrolysis solution; b. Tannic acid modification: Add tannic acid (2 - 4 wt.%) and nano-ceria (0.5 - 1 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and utilize the hydrogen bond interaction between the phenolic hydroxyl group of TA and the hydroxyl group on the surface of the nano-particles to form a stable composite colloid.

[0009] In the ultrasonic alkali cleaning and degreasing with the NaOH solution, the concentration of the NaOH solution is 5 - 10 wt.%, the temperature is 60 - 80 °C, and the ultrasonic cleaning time is 10 - 15 min.

[0010] The green preparation method of the silicon-containing FeCo-based nano-alloy surface composite passivation film of the present invention specifically includes the following processes: S1. Pretreatment process: a. Alkali cleaning and degreasing: Immerse the alloy in a NaOH solution (5 - 10 wt.%) at 60 - 80 °C and ultrasonically clean for 10 - 15 min to remove surface oil stains and oxides; b. Pickling activation: Use a mixed solution of dilute nitric acid (5 - 10 vol.%) and hydrogen peroxide (3 - 5 vol.%), soak at room temperature for 2 - 5 min to form a microscopically rough surface to enhance the film layer adhesion.

[0011] S2. Preparation of silane-tannic acid composite passivation solution: a. Silane hydrolysis: Dissolve silane coupling agents KH560 (10 - 15 wt.%) and KH570 (5 - 8 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 4 - 5, and magnetically stir for 2 - 4 h to form a transparent hydrolysis solution; b. Tannic acid modification: Add tannic acid (2 - 4 wt.%) and nano-ceria (0.5 - 1 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and form a stable composite colloid by the hydrogen bond interaction between the phenolic hydroxyl groups of TA and the hydroxyl groups on the surface of the nanoparticles.

[0012] S3. Passivation film preparation: a. Immersion film formation: Immerse the pretreated alloy in the passivation solution, control the temperature at 25 - 40 °C, the immersion time at 5 - 10 min, and the pulling speed at 1 - 2 mm / s to form a uniform primary film; b. Heat treatment curing: Bake at 80 - 100 °C for 20 - 30 min to promote the silane polycondensation and the chelation reaction between TA and the metal surface, and form a Si-O-M (M is Fe / Co) covalent network.

[0013] S4. Post-treatment strengthening: Use a potassium fluotitanate (0.1 - 0.3 wt.%) solution for sealing treatment to fill the micropores of the film layer and improve the salt spray resistance.

[0014] Through the chemical bonding and physical filling of silane-TA-CeO2, the present invention constructs a "rigid-flexible combination" three-dimensional protection network; the phenolic hydroxyl groups of TA can release chelated metal ions when the local pH increases to repair the film layer defects; and the whole process of this process is water-based, greatly reducing energy consumption and having no toxic substance emissions. Specific embodiments

[0015] The above scheme is further described below in conjunction with specific implementation examples, and the preferred embodiments of the present invention are described in detail as follows: Example 1

[0016] 1. Pretreatment process: a. Alkaline cleaning and degreasing: Immerse the alloy in a NaOH solution (10 wt.%) at 60 °C and ultrasonically clean for 10 min to remove the surface oil and oxides; b. Acid pickling and activation: Use a mixed solution of dilute nitric acid (5 vol.%) and hydrogen peroxide (3 vol.%), soak at room temperature for 5 min to form a microscopically rough surface to enhance the film layer adhesion.

[0017] 2. Preparation of silane-tannic acid composite passivation solution: a. Silane hydrolysis: Dissolve silane coupling agents KH560 (10 wt.%) and KH570 (5 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 4, and magnetically stir for 4 h to form a transparent hydrolysis solution; b. Tannic acid modification: Add tannic acid (2 wt.%) and nano-ceria (0.5 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and form a stable composite colloid by the hydrogen bond interaction between the phenolic hydroxyl group of TA and the hydroxyl group on the surface of the nano-particles.

[0018] 3. Passivation film preparation: a. Dipping film formation: Immerse the pretreated alloy in the passivation solution, control the temperature at 25 °C, the dipping time at 10 min, and the pulling speed at 2 mm / s to form a uniform primary film; b. Heat treatment for curing: Bake at 80 °C for 30 min to promote the silane polycondensation and the chelation reaction between TA and the metal surface, and form a Si-O-M (M is Fe / Co) covalent network.

[0019] 4. Post-treatment strengthening: Use a potassium fluotitanate (0.1 wt.%) solution for sealing treatment to fill the micropores of the film layer and improve the salt spray resistance. Example 2

[0020] 1. Pretreatment process: a. Alkaline cleaning and degreasing: Immerse the alloy in a NaOH solution (8 wt.%) at 70 °C and ultrasonically clean for 15 min to remove the surface oil and oxides; b. Acid pickling and activation: Use a mixed solution of dilute nitric acid (10 vol.%) and hydrogen peroxide (3 vol.%), soak at room temperature for 3 min to form a microscopically rough surface to enhance the film layer adhesion.

[0021] 2. Preparation of silane-tannic acid composite passivation solution: a. Silane hydrolysis: Dissolve silane coupling agents KH560 (15 wt.%) and KH570 (5 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 4.5, and magnetically stir for 3 h to form a transparent hydrolysis solution; b. Tannic acid modification: Add tannic acid (4 wt.%) and nano-ceria (0.5 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and form a stable composite colloid by the hydrogen bond interaction between the phenolic hydroxyl group of TA and the hydroxyl group on the surface of the nano-particles.

[0022] 3. Passivation film preparation: a. Dipping film formation: Immerse the pretreated alloy in the passivation solution, control the temperature at 30 °C, the dipping time at 10 min, and the pulling speed at 1 mm / s to form a uniform primary film; b. Heat treatment and curing: Bake at 100 °C for 20 min to promote the polycondensation of silane and the chelation reaction between TA and the metal surface, forming a Si-O-M (M is Fe / Co) covalent network.

[0023] 4. Post-treatment strengthening: Perform a sealing treatment with a potassium fluotitanate (0.2 wt.%) solution to fill the micropores of the film layer and improve the salt spray resistance. Example 3

[0024] 1. Pretreatment process: a. Alkaline cleaning and degreasing: Immerse the alloy in an 80 °C NaOH solution (5 wt.%) and ultrasonically clean for 10 min to remove surface oil and oxides. b. Acid pickling and activation: Use a mixed solution of dilute nitric acid (5 vol.%) and hydrogen peroxide (5 vol.%), soak at room temperature for 5 min to form a microscopically rough surface to enhance the film layer adhesion.

[0025] 2. Preparation of silane-tannic acid composite passivation solution: a. Silane hydrolysis: Dissolve silane coupling agents KH560 (10 wt.%) and KH570 (8 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 5, and magnetically stir for 4 h to form a transparent hydrolysis solution. b. Tannic acid modification: Add tannic acid (3 wt.%) and nano-ceria (1 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and utilize the hydrogen bond interaction between the phenolic hydroxyl group of TA and the hydroxyl group on the surface of the nano-particles to form a stable composite colloid.

[0026] 3. Preparation of passivation film: a. Dipping film formation: Immerse the pretreated alloy in the passivation solution, control the temperature at 40 °C, dipping time 5 min, and pulling speed 1 mm / s to form a uniform primary film. b. Heat treatment and curing: Bake at 90 °C for 20 min to promote the polycondensation of silane and the chelation reaction between TA and the metal surface, forming a Si-O-M (M is Fe / Co) covalent network.

[0027] 4. Post-treatment strengthening: Perform a sealing treatment with a potassium fluotitanate (0.3 wt.%) solution to fill the micropores of the film layer and improve the salt spray resistance.

[0028] The present invention conducts performance tests such as salt spray tests, electrochemical impedance, and adhesion on the samples in the above embodiments, and the test results are shown in Table 1.

[0029] Table 1. Performance tests of samples in the embodiments Sample Salt spray test (h) <![CDATA[Electrochemical impedance (Ω / cm 2 )]]> Adhesion grade Example 1 91 <![CDATA[1.12×10 5 > 1 Example 2 96 <![CDATA[1.33×10 5 > 0 Example 3 97 <![CDATA[1.37×10 5 > 0 The embodiments described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made by those skilled in the art to the technical solutions of the present invention shall fall within the protection scope of the present invention. The technical content claimed by the present invention has been fully recorded in the claims.

Claims

1. Green preparation method of a silicon-containing FeCo-based nanoalloy surface composite passivation film, including pretreatment, passivation solution preparation, immersion film formation, and post-treatment strengthening. The passivation solution is a silane-tannic acid composite passivation solution. The immersion film formation is to immerse the pretreated alloy into the passivation solution to form a uniform primary film. The primary film is heat-treated and cured to promote the condensation of silane and the chelation reaction between TA and the metal surface, forming a Si-O-M covalent network, where M is Fe / Co. The post-treatment strengthening is to use a potassium fluotitanate solution for sealing treatment to fill the micropores of the film layer and improve the salt spray resistance performance.

2. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that the control temperature for forming the primary film is 25 - 40 °C, the immersion time is 5 - 10 min, and the pulling speed is 1 - 2 mm / s.

3. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that the pretreatment process includes ultrasonic alkali washing with a NaOH solution to remove surface oil stains and oxides and pickling activation with a mixed solution of dilute nitric acid and hydrogen peroxide to form a microscopically rough surface to enhance the film layer adhesion.

4. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that the preparation method of the silane-tannic acid composite passivation solution is: a. Dissolve silane coupling agents KH560 (10 - 15 wt.%) and KH570 (5 - 8 wt.%) in an ethanol-water mixed solvent (volume ratio 3:1), adjust the pH to 4 - 5, and magnetically stir for 2 - 4 h to form a transparent hydrolysis solution. b. Tannic acid modification: Add tannic acid (2 - 4 wt.%) and nano-ceria (0.5 - 1 wt.%) to the hydrolysis solution, ultrasonically disperse for 30 min, and utilize the hydrogen bond interaction between the phenolic hydroxyl group of TA and the hydroxyl group on the surface of the nano-particles to form a stable composite colloid.

5. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that in the ultrasonic alkali washing and degreasing with the NaOH solution, the concentration of the NaOH solution is 5 - 10 wt.%, the temperature is 60 - 80 °C, and the ultrasonic cleaning time is 10 - 15 min.

6. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that the heat treatment and curing of the primary film adopt a low-temperature curing mechanism, baking at 80 - 100 °C for 20 - 30 min.

7. The green preparation method of the silicon-containing FeCo-based nanoalloy surface composite passivation film according to claim 1, characterized in that the concentration of the potassium fluotitanate solution in the post-treatment strengthening is 0.1 - 0.3 wt.%.