A strong corrosion-resistant al-zr alloy double-layer anodic oxidation layer and a preparation method thereof

Abstract

The application discloses a kind of strong corrosion-resistant Al-Zr alloy double-layer anodic oxidation layer and preparation method thereof, comprising: Al-Zr alloy pretreatment;With the pretreated Al-Zr alloy as anode, platinum wire as cathode, it is immersed in electrolyte solution with temperature of 20 DEG C-30 DEG C and carries out anodic oxidation, with 1.67V / S-6.67V / S linear voltage increasing speed, voltage is linearly increased from 0V to 50V-200V and then kept for 600s, to form crystalline Al2O3 layer on alloy surface and form amorphous Al2O3 layer on the surface of crystalline Al2O3 layer.The application realizes one-step preparation of double-layer anodic oxidation layer, and by setting linear voltage increasing and regulating to reach target voltage and keeping for 600s, can effectively improve the oxidation resistance of alloy under high temperature condition and the corrosion resistance under severe environment;Amorphous Al2O3 layer can effectively hinder atomic diffusion, improve the stability of alloy.

Description

Technical Field

[0001] This invention relates to the field of materials processing technology, and more specifically, to a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer and its preparation method. Background Technology

[0002] Heat-resistant Al-Zr alloys have become the preferred material for high-voltage overhead transmission lines both domestically and internationally due to their excellent heat resistance, tensile strength, and sag characteristics. However, naturally grown oxide layers offer extremely limited protection to the alloy under harsh service environments, and the insufficient surface properties of Al-Zr heat-resistant alloys severely restrict their long-term stable service. Controlled pre-oxidation treatment improves the mechanical properties, corrosion resistance, tribological properties, and catalytic activity of the material surface in an efficient and economical way. Common methods for preparing oxide layers on aluminum alloy surfaces include thermal oxidation, anodizing, chemical oxidation, and micro-arc oxidation. Among these, anodizing involves a chemical reaction on the metal surface, directly transforming the substrate surface into an oxide film. Therefore, compared to oxide deposition spraying, the prepared oxide layer has the advantages of good adhesion to the alloy and more uniform thickness, and is widely used for surface pretreatment of aluminum alloys.

[0003] Existing anodizing techniques generate a single-layer anodic oxide layer on the alloy surface, which has insufficient corrosion resistance and oxidation resistance, especially in high-temperature environments where corrosion is highly likely to occur, leading to a rapid decrease in alloy stability. Furthermore, traditional anodizing techniques use a fixed voltage; instantaneous high voltage can result in an uneven oxide film with numerous defects.

[0004] Therefore, how to prepare Al-Zr alloy materials that have corrosion resistance and oxidation resistance in high-temperature environments, while ensuring the stability of Al-Zr alloy materials, has become a major technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned defects in the prior art and provide a highly corrosion-resistant double-layer anodic oxide layer of Al-Zr alloy and its preparation method. Utilizing anodic oxidation, a one-step process is achieved to form a crystalline Al2O3 layer on the surface of the Al-Zr alloy and an amorphous Al2O3 layer on the surface of the crystalline Al2O3 layer. By setting a linear voltage boost to ensure a linear increase in the initial voltage and maintaining it for 600 seconds after reaching the target voltage, the oxidation resistance of the Al-Zr alloy under high-temperature conditions and its corrosion resistance in harsh environments can be effectively improved. The amorphous Al2O3 layer can effectively hinder atomic diffusion and improve the stability of the Al-Zr alloy.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer includes the following steps:

[0008] (1) After grinding and polishing, Al-Zr alloy is ultrasonically cleaned with ethanol and acetone, and then subjected to alkali washing, acid washing, water washing and drying in sequence to obtain pretreated Al-Zr alloy.

[0009] (2) Using the pretreated Al-Zr alloy as the anode and the platinum wire as the cathode, the alloy is immersed in an electrolyte solution at a temperature of 20℃~30℃ for anodizing. The voltage is linearly increased from 0V to the target voltage of 50V~200V at a linear voltage increase rate of 1.67V / S~6.67V / S and held for 600s to form a crystalline Al2O3 layer on the surface of the pretreated Al-Zr alloy and an amorphous Al2O3 layer on the surface of the crystalline Al2O3 layer, thus obtaining the double-layer anodized Al-Zr alloy.

[0010] Optionally, step (1) specifically includes:

[0011] The Al-Zr alloy was ground using SiC sandpaper with grit sizes of 1000, 1500, 2000, 2500 and 3000 to obtain the ground Al-Zr alloy.

[0012] The ground Al-Zr alloy was polished to a mirror finish using diamond polishing paste and silica suspension to obtain the polished Al-Zr alloy.

[0013] The polished Al-Zr alloy was ultrasonically cleaned sequentially with acetone and ethanol, then alkaline cleaned with 10% NaOH solution and acid cleaned with 10% HNO3 solution to remove oil, followed by water washing (18×10). 6 The Ωcm alloy was dried by compressed N2 gas and then placed in a drying oven for 24 hours to obtain the pretreated Al-Zr alloy.

[0014] Optionally, in step (1), the particle size of the diamond polishing paste is 1.5μm to 3.5μm; and the particle size of the silica in the silica suspension is 20nm to 50nm.

[0015] Optionally, in step (2), the preparation of the electrolyte solution includes the following steps: preparing a 0.1 mol / L citric acid solution using deionized water and citric acid granules, and adjusting the pH of the citric acid solution to 5.8 using a 1 mol / L sodium hydroxide solution to obtain the electrolyte solution.

[0016] Optionally, in step (2), the surface area of ​​the platinum wire is 1.6 cm². 2 .

[0017] Optionally, in step (2), the linear boost rate is 3.33V / S to 6.67V / S; and the target voltage is 100V to 200V.

[0018] Optionally, the Al-Zr alloy is Al-xZr, wherein x≤1 includes one of Al-0.2Zr, Al-0.5Zr and Al-1Zr alloys; preferably, Al-xZr is an Al-0.2Zr, Al-0.5Zr or Al-1Zr alloy.

[0019] Optionally, the thickness of the crystalline Al2O3 layer is 15nm to 55nm; the thickness of the amorphous Al2O3 layer is 50nm to 200nm.

[0020] Optionally, the linear boost in step (2) can be controlled using LabVIEW software.

[0021] The present invention also discloses a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer prepared by the preparation method described above, wherein the Al-Zr alloy double-layer anodic oxide layer comprises a crystalline Al2O3 layer formed on the surface of the Al-Zr alloy and an amorphous Al2O3 layer formed on the surface of the crystalline Al2O3 layer.

[0022] Implementing the embodiments of the present invention will have the following beneficial effects:

[0023] The preparation method provided by this invention, compared to the single oxide layer formed by traditional anodizing, uses a linear voltage ramp to ensure a linear increase in the initial voltage, thereby avoiding uneven oxide film and excessive defects caused by instantaneous high voltage. Furthermore, by maintaining the target voltage for 600 seconds after reaching it, the Al-Zr alloy undergoes anodizing treatment, resulting in a uniform and dense bilayer structure of crystalline and amorphous Al2O3 layers on the Al-Zr alloy surface. This effectively improves the oxidation resistance of the Al-Zr alloy under high-temperature conditions and its corrosion resistance in harsh environments. The amorphous Al2O3 layer effectively hinders atomic diffusion, improving the stability of the Al-Zr alloy and increasing its service life. Simultaneously, this invention features more refined pretreatment of the Al-Zr alloy surface and a more scientific preparation of the electrolyte solution, effectively reducing surface defects in the oxide layer.

[0024] This invention requires only one anodizing process to form a double-layer anodized layer on the surface of Al-Zr alloy. The preparation process is simple and easy to control, and does not require high temperature and high pressure conditions. The raw materials are readily available and inexpensive, making it suitable for industrial production and promotion. Attached Figure Description

[0025] Figure 1Characteristic transient curves of the anodizing process of Al-1Zr alloy. At different final voltages of 50V (red), 100V (blue), 150V (green), and 200V (purple), (a) curves showing the change of current density over time during the anodizing process, and (b) curves showing the change of voltage over time during the anodizing process.

[0026] Figure 2 Scanning electron microscope (SEM) images of the anodic oxide layer surfaces of Al-Zr alloy grown at (a) 50V and (b) 200V.

[0027] Figure 3 AES in-depth images of (a) Al-0.2Zr, (b) Al-0.5Zr and (c) Al-1Zr alloys after anodizing at 200V.

[0028] Figure 4 (a) Cross-sectional transmission electron microscope (TEM) image of the anodic oxide layer of Al-1Zr alloy grown at 200V; (b) and (c) are high-resolution images (HRTEM) of crystalline Al2O3 and amorphous Al2O3 oxide layers, respectively, and EDX elemental surface scan images (d).

[0029] Figure 5 Polarization test diagram of Al-1Zr alloy after anodizing treatment in 3.5 wt.% NaCl solution.

[0030] Figure 6 Electrochemical impedance spectroscopy (EIS) of oxidized Al-1Zr alloy in 3.5 wt.% NaCl solution: (a) Nyquist plot; (b) and (c) Bode plot; (d) equivalent circuit diagram. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0032] Example 1

[0033] Al-1Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer on the sample surface were ground with SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2 Using a platinum wire as the cathode, in a 0.1 mol / L citric acid solution (pH adjusted by a 1 mol / L sodium hydroxide solution), at a temperature of 25 ± 5 °C, LabVIEW software was used to linearly increase the voltage from 0 V to a target voltage of 200 V within 30 seconds, and then maintain the target voltage of 200 V for 600 seconds (e.g., ...). Figure 1 (b) shows the corresponding current density as follows: Figure 1 As shown in (a), the preparation of the double-layer anodic oxide layer is completed when the oxidation time ends, and the surface microstructure of the oxide layer is as follows. Figure 2 As shown in (b), the microstructure of the oxide layer cross-section is as follows: Figure 4 As shown. By Figure 4 TEM revealed that the oxide layer structure is of two types: the oxide layer adjacent to the substrate is crystalline, and the oxide layer above the crystalline oxide layer is amorphous. Figure 3 (c) AES depth profiling was performed on the obtained oxide layer to determine the elemental composition along the depth direction, specifically the Al2O3 layer. Polarization and electrochemical impedance spectroscopy were performed on the oxidized sample in 3.5% NaCl solution. The test results are as follows: Figure 5 and Figure 6 As shown, Figure 6 (d) The equivalent circuit also verified the existence of the double oxide film. Table 1 shows the Tafel fitting data of the polarization curves, and Table 2 shows the fitting data of the electrochemical impedance spectroscopy. From the test results and fitting data, it can be seen that the oxide layer after anodic oxidation at 200V is the thickest, the corrosion potential is the highest, the current density is the lowest, and the corrosion resistance is the best.

[0034] Example 2

[0035] Al-1Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer on the sample surface were ground with SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6 The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2Using a platinum wire as the cathode, in a 0.1 mol / L citric acid solution (pH adjusted with a 1 mol / L sodium hydroxide solution), at a temperature of 25 ± 5 °C, LabVIEW software was used to linearly increase the voltage from 0 V to a target voltage of 50 V within 30 seconds, and then maintain the target voltage of 50 V for 600 seconds (voltage as follows). Figure 1 (b) shows the corresponding current density as follows: Figure 1 As shown in (a), the preparation of the double-layer anodic oxide layer is completed when the oxidation time ends, and the surface microstructure of the oxide layer is as follows. Figure 2 As shown in (a), the oxidized sample was subjected to polarization and electrochemical impedance spectroscopy tests in a 3.5% NaCl solution. The test results are as follows. Figure 5 and Figure 6 As shown, Figure 6 (d) The equivalent circuit also verified the existence of the double oxide film. Table 1 shows the Tafel fitting data of the polarization curves, and Table 2 shows the fitting data of the electrochemical impedance spectroscopy. The test results and fitting data show that the oxide layer after 50V anodic oxidation is thinner, has a lower corrosion potential, a higher current density, and its corrosion resistance is somewhat reduced, but it still exhibits excellent corrosion resistance.

[0036] Example 3

[0037] Al-1Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer on the sample surface were ground with SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6 The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2 Using a platinum wire as the cathode, in a 0.1 mol / L citric acid solution (pH adjusted with a 1 mol / L sodium hydroxide solution), at a temperature of 25 ± 5 °C, LabVIEW software was used to linearly increase the voltage from 0 V to a target voltage of 100 V within 30 seconds, and then maintain the target voltage of 100 V for 600 seconds (voltage as follows). Figure 1 (b) shows the corresponding current density as follows: Figure 1 As shown in (a), the preparation of the double-layer anodic oxide layer is complete upon the end of the oxidation time. The oxidized sample was subjected to polarization and electrochemical impedance spectroscopy tests in a 3.5% NaCl solution. The test results are as follows: Figure 5 and Figure 6 As shown, Figure 6 (d) The equivalent circuit also verified the existence of the double oxide film. Table 1 shows the Tafel fitting data of the polarization curves, and Table 2 shows the fitting data of the electrochemical impedance spectroscopy.

[0038] Example 4

[0039] Al-1Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer on the sample surface were ground with SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6 The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2 Using a platinum wire as the cathode, in a 0.1 mol / L citric acid solution (pH adjusted with a 1 mol / L sodium hydroxide solution), at a temperature of 25 ± 5 °C, LabVIEW software was used to linearly increase the voltage from 0 V to a target voltage of 150 V within 30 seconds, and then maintain the target voltage of 150 V for 600 seconds (voltage as follows). Figure 1 (b) shows the corresponding current density as follows: Figure 1 As shown in (a), the preparation of the double-layer anodic oxide layer is complete upon the end of the oxidation time. Polarization and electrochemical impedance spectroscopy were performed on the oxidized sample in a 3.5% NaCl solution. The test results are as follows: Figure 5 and Figure 6 As shown, Figure 6 (d) The equivalent circuit also verified the existence of the double oxide film. Table 1 shows the Tafel fitting data of the polarization curves, and Table 2 shows the fitting data of the electrochemical impedance spectroscopy.

[0040] Example 5

[0041] Al-0.5Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer were removed from the sample surface using SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6 The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2 A platinum wire was used as the cathode. In a 0.1 mol / L citric acid solution (pH adjusted with 1 mol / L sodium hydroxide solution), at a temperature of 25 ± 5 °C, LabVIEW software was used to linearly increase the voltage from 0 V to a target voltage of 200 V within 30 seconds. This target voltage was then maintained at 200 V for 600 seconds. The oxidation time ended, completing the preparation of the double-layer anodic oxide layer. TEM analysis revealed two oxide layer structures: a crystalline oxide layer adjacent to the substrate and an amorphous oxide layer above it. Figure 3 (b) In order to perform AES depth analysis on the obtained oxide layer, the elemental content in the depth direction of the oxide layer was found to be Al2O3 layer, which is the thickest layer.

[0042] Example 6

[0043] Al-0.2Zr alloy ingots were cut into 15mm × 15mm × 5mm blocks using wire cutting. The wire cutting marks and surface oxide layer were removed from the sample surface using SiC sandpaper (1000, 1500, 2000, 2500, and 3000 grit). The samples were then polished to a mirror finish using diamond polishing paste (1.5-3.5μm) and silica suspension (50nm), respectively. After polishing, the samples were ultrasonically cleaned sequentially in acetone and ethanol, followed by alkaline cleaning with 10% NaOH solution and acid cleaning with 10% HNO3 solution to remove oil. After alkaline and acid cleaning, the samples were rinsed with deionized water (18 × 10⁻⁶ grit). 6 The alloy was rinsed with Ωcm, then dried with compressed N2 gas and placed in a drying oven for 24 hours. The pretreated Al-Zr alloy was used as the anode, with a surface area of ​​1.6 cm². 2Using platinum wire as the cathode, in a citric acid solution with a pH of 5.8 and a concentration of 0.1 mol / L (pH adjuster is a 1 mol / L sodium hydroxide solution), at a temperature of 25±5℃, the voltage is controlled by LabVIEW software to linearly increase from 0V to the target voltage of 200V within 30s, and then maintained at the target voltage of 200V for 600s. The preparation of the double-layer anodic oxide layer is completed when the oxidation time ends. Figure 3 (a) To perform AES depth analysis on the obtained oxide layer, the elemental content in the depth direction of the oxide layer was found to be Al2O3 layer, which is the thinnest layer.

[0044] Table 1. Fitting parameters of electrochemical impedance spectroscopy for Al-1Zr alloy after anodizing.

[0045]

[0046] Table 2. Polarization test fitting parameters of Al-1Zr alloy after anodizing.

[0047]

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer, characterized in that, Includes the following steps: (1) After grinding and polishing, Al-Zr alloy is ultrasonically cleaned with ethanol and acetone, and then successively subjected to alkaline washing, acid washing, water washing and drying to obtain pretreated Al-Zr alloy. (2) The pretreated Al-Zr alloy is used as the anode and the platinum wire is used as the cathode. The alloy is immersed in an electrolyte solution at a temperature of 20℃~30℃ for anodic oxidation. The voltage is linearly increased from 0V to the target voltage of 100V~200V at a linear voltage increase rate of 3.33V / S~6.67V / S and held for 600s to form a crystalline Al2O3 layer on the surface of the pretreated Al-Zr alloy and an amorphous Al2O3 layer on the surface of the crystalline Al2O3 layer. The crystalline Al2O3 layer and the amorphous Al2O3 layer are uniform and dense, thus obtaining the double-layer anodic oxide layer of the Al-Zr alloy. In step (2), the preparation of the electrolyte solution includes the following steps: preparing a 0.1 mol / L citric acid solution using deionized water and citric acid granules, and adjusting the pH of the citric acid solution to 5.8 using a 1 mol / L sodium hydroxide solution to obtain the electrolyte solution.

2. The method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer according to claim 1, characterized in that, Step (1) specifically includes: The Al-Zr alloy was ground using SiC sandpaper to obtain the ground Al-Zr alloy. The ground Al-Zr alloy was polished to a mirror finish using diamond polishing paste and silica suspension to obtain the polished Al-Zr alloy. The polished Al-Zr alloy was ultrasonically cleaned with acetone and ethanol in sequence, then alkaline washed with 10% NaOH solution and acid washed with 10% HNO3 solution to remove oil. The alloy was then washed with water, and finally dried with compressed N2 gas and placed in a drying oven for 24 hours to obtain the pretreated Al-Zr alloy.

3. The method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer according to claim 2, characterized in that, In step (1), the particle size of the diamond polishing paste is 1.5μm~3.5μm; the particle size of the silica in the silica suspension is 20nm~50nm.

4. The method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer according to claim 1, characterized in that, In step (2), the surface area of ​​the platinum wire is 1.6 cm². 2 .

5. The method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer according to claim 1, characterized in that, The Al-Zr alloy is Al-xZr, where x≤1.

6. The method for preparing a highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer according to claim 1, characterized in that, The thickness of the crystalline Al2O3 layer is 15nm~55nm; the thickness of the amorphous Al2O3 layer is 50nm~200nm.

7. A highly corrosion-resistant Al-Zr alloy double-layer anodic oxide layer prepared by the preparation method according to any one of claims 1-6, characterized in that, The Al-Zr alloy double-layer anodic oxide layer includes a crystalline Al2O3 layer formed on the surface of the Al-Zr alloy and an amorphous Al2O3 layer formed on the surface of the crystalline Al2O3 layer.

Images