A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material

Abstract

This invention relates to a method for preparing a corrosion-resistant coating for TiB2-reinforced Al-based composite materials, belonging to the field of metal surface treatment technology. The corrosion-resistant coating for TiB2-reinforced Al-based composite materials of this invention includes an anodic aluminum oxide ceramic underlayer and an Al2O3 / La2O3 / silane coating film prepared on the surface of the TiB2-reinforced Al-based composite material. Using anodic aluminum oxide as the underlayer improves the adhesion between the coating layers. The Al2O3 / La2O3 / silane coating, synthesized by hydrothermal co-precipitation, can seal the pores of the anodic oxide film while forming a thin film on the surface with good corrosion resistance, thus increasing barrier properties, sealing pores, and improving the corrosion resistance of the coating. The composite coating of this invention overcomes the defect of difficulty in forming a uniform and dense Al2O3 oxide film on the surface of TiB2-reinforced particles, resulting in a protective coating with good corrosion resistance.

Description

Technical Field

[0001] This invention relates to a method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, belonging to the field of metal surface treatment technology. Background Technology

[0002] Aluminum alloys possess a range of excellent properties, including low density, high strength, and moderate fatigue resistance, and are widely used in aerospace, rail transportation, defense, and shipbuilding industries. Compared to traditional aluminum alloys, aluminum-based composites exhibit superior advantages such as high specific strength / stiffness, high elastic modulus, fatigue resistance, and wear resistance due to the introduction of reinforcing phases. However, the oxide film on the surface of aluminum alloys is susceptible to corrosion in environments containing chloride ions, leading to pitting corrosion, intergranular corrosion, and stress corrosion. Recent research indicates that ceramic particles can enhance the microstructure and properties of aluminum alloys, with TiB2 considered an ideal reinforcing agent for aluminum-based composites due to its high melting point, high hardness, and favorable grain boundary structure. The in-situ addition of TiB2 particles can significantly strengthen aluminum alloys; however, the potential difference between the TiB2 particles and the aluminum matrix acts as a cathode, promoting rapid dissolution of the matrix and fostering pitting corrosion, thus reducing the corrosion resistance of Al-based composites.

[0003] Surface treatment technology, as the most effective method for corrosion protection of aluminum alloys, is widely used in the field of aluminum alloy corrosion protection. There are various surface treatment methods for aluminum, with commonly used surface modification methods including electroplating, anodizing, micro-arc oxidation, and laser cladding. The specific method depends on the intended use in various operating environments. Among the many surface treatment methods, anodizing is simple, produces a relatively uniform oxide film, and has good mechanical properties. The anodizing process is affected by various factors, including electrolyte properties, oxidation temperature, and oxidation time. However, previous studies on the electrochemical properties of anodized aluminum materials have shown that due to the formation of a weak barrier oxide film, TiB2-reinforced Al-based composites have low applicability to anodizing treatment, and simple anodizing treatment cannot significantly improve the corrosion resistance of the alloy surface. Furthermore, the complexity of the microstructure of TiB2-reinforced Al-based composites greatly affects the uniformity and integrity of the oxide film, further reducing corrosion resistance. Therefore, researching effective protection methods to improve the corrosion resistance of in-situ self-generated TiB2-reinforced Al-based composites has become an important task in this field. Summary of the Invention

[0004] To address the technical problem of insufficient uniformity and integrity of the oxide film prepared by anodic oxidation due to the complexity of the microstructure of TiB2-reinforced Al-based composite materials, resulting in low corrosion resistance, this invention proposes a method for preparing a corrosion-resistant coating for TiB2-reinforced Al-based composite materials. The corrosion-resistant coating comprises an anodic aluminum oxide ceramic underlayer and an Al2O3 / La2O3 / silane coating film prepared on the surface of the TiB2-reinforced Al-based composite material. Using anodic aluminum oxide as the underlayer improves the adhesion between the coating layers. The Al2O3 / La2O3 / silane coating, synthesized by hydrothermal co-precipitation, can seal the pores of the anodic oxide film while forming a thin film on the surface with good corrosion resistance, thus increasing barrier properties, sealing pores, and improving the coating's corrosion resistance. This composite coating overcomes the defect of difficulty in forming a uniform and dense Al2O3 oxide film on the surface of TiB2-reinforced particles, resulting in a protective coating with good corrosion resistance.

[0005] A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, the specific steps of which are as follows:

[0006] (1) The surface of TiB2 reinforced Al-based composite material was pretreated to obtain surface-pretreated TiB2 reinforced Al-based composite material;

[0007] (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode are immersed in electrolyte A for anodic oxidation, and a porous Al2O3 ceramic coating is obtained on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contains H2SO4, C6H8O7, Al(SO4)3, Ce(SO4)2 and glycerol;

[0008] (3) Dissolve zinc nitrate, aluminum nitrate, lanthanum nitrate and cysteine ​​in deionized water to form a mixed solution. Heat the mixed solution to 60~95℃ and keep it at that temperature for 1~8h. Adjust the pH of the system to 9.5~10.5 with NOH solution to obtain solution B.

[0009] (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to deionized water-ethanol solution and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 3.5-4.5 with nitric acid and ammonia. Hydrolyze the solution at 25-90℃ for 24-48h to obtain silane solution C.

[0010] (5) Mix solution B and silane solution C thoroughly to obtain solution D;

[0011] (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface is placed in solution D and sealed. The temperature is raised to 110~150℃ and kept at the temperature for 6~12h to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

[0012] Preferably, the surface pretreatment method in step (1) is as follows: the surface of the TiB2 reinforced Al-based composite material is sanded with sandpaper, then added to NaOH solution, alkali soaked at 60~85℃ for 5~60s, then added to hydrochloric acid~nitric acid mixed acid solution for activation treatment for 1~5min, washed with deionized water and stored in anhydrous ethanol for later use.

[0013] More preferably, the concentration of the NaOH solution is 0.5~2 mol / L, and the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution is 0.5~1.5 mol / L, and the concentration of nitric acid is 3~6 mol / L.

[0014] Preferably, in step (2), the electrolyte A contains 150-200 g / L H2SO4, 10-20 g / L C6H8O7, 1-8 g / L Al(SO4)3, 1-10 g / L Ce(SO4)2, and 5-15 g / L glycerol, and the solvent is deionized water.

[0015] More preferably, the distance between the anode electrode and the cathode electrode is 5~10nm, the forward constant voltage for anodizing is 10~60V, and the anodizing time is 10~60min.

[0016] Preferably, the mixed solution in step (3) contains 8~15g / L zinc nitrate, 1~10g / L aluminum nitrate, 0.5~2g / L lanthanum nitrate, and 1~10g / L cysteine.

[0017] Preferably, the mixture in step (4) contains 50-150 ml / L of γ-aminopropyltriethoxysilane and 1-4 g / L of lanthanum nitrate.

[0018] Preferably, in step (5), the silane solution C accounts for 5-40% of the volume of solution B.

[0019] The beneficial effects of this invention are:

[0020] (1) The present invention uses sulfuric acid (H2SO4), citric acid (C6H8O7), aluminum sulfate (Al(SO4)3), cerium sulfate tetrahydrate (Ce(SO4)2·4H2O), and glycerol (C3H8O3) as a composite acid electrolyte, which can improve the performance of TiB2-reinforced Al-based composite anodic oxide film; improve the formation efficiency of oxide film, reduce the pores and defects on the oxide film surface, and increase the density of oxide film;

[0021] (2) The present invention adds glycerol, an organic additive, to change the chemical or electrochemical behavior of TiB2 reinforced Al-based composite material during the anodic oxidation process, thereby reducing the dissolution rate and porosity of the film. The addition of rare earth salt (Ce(SO4)2·4H2O) can increase the thickness of the barrier layer.

[0022] (3) This invention utilizes the property of silane coupling agent to react with functional groups on the surface of metals and their oxides to improve the dispersion and stability of its components in the matrix. An Al2O3 / La2O3 / silane coating is prepared on the anodic oxide film by hydrothermal co-deposition. The Al2O3 / La2O3 seals the pores and density of the anodic oxide film. At the same time, the Al2O3 / La2O3 / silane coating generated on the surface of the anodic oxide film can block its contact with the corrosive solution and enhance its corrosion resistance.

[0023] (4) The corrosion-resistant coating of the TiB2-reinforced Al-based composite material of the present invention was electrochemically tested in 3.5% NaCl solution. Its corrosion current was reduced by two orders of magnitude compared with the untreated TiB2-reinforced Al-based composite material, and by about 100 times compared with the anodized TiB2-reinforced Al-based composite material. The corrosion resistance is very significant. Attached Figure Description

[0024] Figure 1 The potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 1 are shown.

[0025] Figure 2 The potentiodynamic polarization curves of TiB2-reinforced Al-based composite materials with different surface treatments in Example 2 are shown.

[0026] Figure 3 EIS results of TiB2-reinforced Al-based composites with different surface treatments in Example 2;

[0027] Figure 4 The image shows the SEM morphology and EDS composition of the Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 2.

[0028] Figure 5 The potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 3 are shown.

[0029] Figure 6 The image shows the potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 4. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0031] Example 1: A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, the specific steps of which are as follows:

[0032] (1) The surface of the TiB2 reinforced Al-based composite material is pretreated to obtain the surface-pretreated TiB2 reinforced Al-based composite material. The surface pretreatment method is as follows: the surface of the TiB2 reinforced Al-based composite material is polished with sandpaper, then added to a NaOH solution with a concentration of 1 mol / L, and alkali soaked at 60℃ for 5s. Then it is added to a hydrochloric acid-nitric acid mixed acid solution (the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution is 0.5 mol / L and the concentration of nitric acid is 3 mol / L) for activation treatment for 1 min. After being washed with deionized water, it is stored in anhydrous ethanol for later use.

[0033] (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode are immersed in electrolyte A (the distance between the anode electrode and the cathode electrode is 5 nm), and anodizing is performed for 10 min under a positive constant voltage of 10 V to obtain a porous Al2O3 ceramic coating on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contains 160 g / L sulfuric acid H2SO4, 10 g / L citric acid C6H8O7, 31 g / L aluminum sulfate Al(SO4), 21 g / L cerium sulfate Ce(SO4), 5 g / L glycerol, and deionized water as the solvent;

[0034] (3) Dissolve zinc nitrate Zn(NO3)2, aluminum nitrate Al(NO3)3, lanthanum nitrate La(NO3)3, and cysteine ​​(Cys) in deionized water to form a mixed solution. Heat the mixed solution to 60°C and keep it at that temperature for 3 hours. Adjust the pH of the system to 10.5 using NOH solution to obtain solution B. The mixed solution contains 28 g / L zinc nitrate Zn(NO3), 1 g / L aluminum nitrate Al(NO3), 31 g / L lanthanum nitrate La(NO3), and 1 g / L cysteine ​​(Cys).

[0035] (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to a deionized water-ethanol solution (the volume ratio of deionized water to ethanol is 1:1) and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 4.5 using nitric acid and ammonia. Hydrolyze the solution at 35°C for 24 hours to obtain silane solution C. The mixed solution contains 60 ml / L of γ-aminopropyltriethoxysilane and 1 g / L of lanthanum nitrate.

[0036] (5) Mix solution B and silane solution C evenly to obtain solution D; the silane solution C accounts for 5% of the volume of solution B;

[0037] (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface was placed in solution D and sealed. The temperature was raised to 110°C and kept at the temperature for 6 hours to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

[0038] The polarization curve of the sample was detected at room temperature using a three-electrode system. The sample under test was used as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum sheet as the counter electrode. 3.5 wt.% NaCl solution was used as the electrolyte. The voltage scan range was set to OCP±0.25V and the scan rate was 2mV / s.

[0039] The potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 1 are shown below. Figure 1 ,from Figure 1 As can be seen from the diagram, the polarization curve represents the relationship between electrode potential and polarization current density, revealing the basic laws of metal corrosion. The ease of material corrosion is evaluated through self-corrosion potential and self-corrosion current density. Self-corrosion current indicates the rate of corrosion; the lower the self-corrosion current, the better the corrosion resistance. Compared to the untreated original sample, the polarization curve of the surface-treated sample in Example 1 shifts downward, indicating that the anodic oxide + Al2O3 / La2O3 / silane coating generated after surface treatment reduces the self-corrosion current density of the composite material, thus improving its corrosion resistance.

[0040] The Ecor and icorr data of the TiB2-reinforced Al-based composite material in this embodiment are shown in Table 1.

[0041] Table 1. Ecor and icorr data of the surface-treated TiB2-reinforced Al-based composite material in this embodiment.

[0042] Corrosion voltage (V) Corrosion current density (μA·cm²) Untreated surface ~0.799 24.93 Anodizing + Al2O3 / La2O3 / silane coating ~0.763 0.7336

[0043] Table 1 shows that the corrosion potentials of the untreated and surface-treated anodic oxide + Al2O3 / La2O3 / silane coatings obtained in this example are ~0.799V and ~0.763V, respectively. While the corrosion voltages of the samples are similar, their corrosion currents differ significantly. The corrosion current density of the untreated sample is 24.93 μA·cm⁻¹. ~2 The corrosion current density of the anodized Al2O3 / La2O3 / silane coating is 0.7336 μA·cm. ~2Compared to the original sample, the corrosion rate decreased by approximately 30 times. Based on Faraday's law, which states that the electrochemical corrosion rate increases linearly with corrosion current density, the lower the corrosion current density, the slower the corrosion rate of the alloy and the better its corrosion resistance. This indicates that anodic oxidation combined with an Al₂O₃ / La₂O₃ / silane coating improves the corrosion resistance of TiB₂-reinforced Al-based composite materials. Figure 1 The polarization curve results correspond to these.

[0044] Example 2: A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, the specific steps of which are as follows:

[0045] (1) The surface of the TiB2 reinforced Al-based composite material was pretreated to obtain the surface-pretreated TiB2 reinforced Al-based composite material. The surface pretreatment method was as follows: the surface of the TiB2 reinforced Al-based composite material was sanded with sandpaper, then added to a NaOH solution with a concentration of 1.25 mol / L, and alkali soaked at 70℃ for 20s. Then it was added to a hydrochloric acid-nitric acid mixed acid solution (the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution was 1 mol / L and the concentration of nitric acid was 4.5 mol / L) for activation treatment for 2min. After being washed with deionized water, it was stored in anhydrous ethanol for later use.

[0046] (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode were immersed in electrolyte A (the distance between the anode electrode and the cathode electrode was 8 nm), and anodizing was performed for 30 min under a positive constant voltage of 15 V to obtain a porous Al2O3 ceramic coating on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contained 180 g / L of sulfuric acid H2SO4, 15 g / L of citric acid C6H8O7, 35 g / L of aluminum sulfate Al(SO4), 25 g / L of cerium sulfate Ce(SO4), and 9 g / L of glycerol, and the solvent was deionized water;

[0047] (3) Dissolve zinc nitrate Zn(NO3)2, aluminum nitrate Al(NO3)3, lanthanum nitrate La(NO3)3, and cysteine ​​(Cys) in deionized water to form a mixed solution. Heat the mixed solution to 70°C and keep it at that temperature for 6 hours. Adjust the pH of the system to 10 using NOH solution to obtain solution B. The mixed solution contains 12 g / L zinc nitrate Zn(NO3)2, 6 g / L aluminum nitrate Al(NO3)3, 1.78 g / L lanthanum nitrate La(NO3)3, and 2.5 g / L cysteine ​​(Cys).

[0048] (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to a deionized water-ethanol solution (the volume ratio of deionized water to ethanol is 1:1) and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 4 using nitric acid and ammonia. Hydrolyze the solution at 25°C for 24 hours to obtain silane solution C. The mixed solution contains 100 ml / L of γ-aminopropyltriethoxysilane and 2 g / L of lanthanum nitrate.

[0049] (5) Mix solution B and silane solution C evenly to obtain solution D; the silane solution C accounts for 10% of the volume of solution B;

[0050] (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface was placed in solution D and sealed. The temperature was raised to 120°C and kept at the temperature for 9 hours to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

[0051] Electrochemical tests on the coating were conducted using a CHI760e electrochemical workstation. A typical three-electrode system was employed, with the sample, platinum electrode, and saturated calomel electrode (SCE) used as the working electrode, auxiliary electrode, and reference electrode, respectively. The corrosion electrolyte was a 3.5% NaCl aqueous solution, the voltage scan range was set to OCP ± 0.25 V, and the scan rate was 1 mV / s. The polarization curves and impedance spectra obtained from the electrochemical tests were used to reflect the corrosion resistance of the coating.

[0052] The potentiodynamic polarization curves of the TiB2-reinforced Al-based composite materials with different surface treatments in this embodiment are shown below. Figure 2 ;from Figure 2 It can be seen that, compared with the untreated original sample, the polarization curve of the anodic oxide + Al2O3 / La2O3 / silane coating shifts downwards overall, and the shift is significant. This indicates that the anodic oxide + Al2O3 / La2O3 / silane coating, after surface treatment, significantly reduces the self-corrosion current density of the composite material and greatly improves its corrosion resistance. Furthermore, it can be observed that the polarization curve of the anodic oxide + Al2O3 / La2O3 / silane coating exhibits a clear corrosion current density plateau between ~0.8V and ~0.7V, indicating good passivation and thus better corrosion resistance.

[0053] The Ecor and icorr data of TiB2-reinforced Al-based composites with different surface treatments in this embodiment are shown in Table 2.

[0054] Table 2. Ecor and icorr data of TiB2-reinforced Al-based composites with different surface treatments.

[0055] Corrosion voltage (V) Corrosion current density (μA·cm²) Untreated surface ~0.799 24.93 Anodizing only ~0.747 3.413 Anodizing + Al2O3 / La2O3 / silane coating ~0.830 0.01054

[0056] Table 2 shows that the corrosion potentials of the untreated sample, the anodized sample only, and the anodized sample with an Al2O3 / La2O3 / silane coating are ~0.799V, ~0.747V, and ~0.830V, respectively. The corrosion voltages of the three samples are not significantly different, but their corrosion currents differ considerably. The corrosion current density of the untreated sample is 24.93 μA·cm⁻¹. ~2 The corrosion current density for anodizing alone is 3.413 μA·cm. ~2 The corrosion current density decreased by 8 times compared to the original sample; the corrosion current density of the anodic oxidation + Al2O3 / La2O3 / silane coating was 0.01054 μA·cm. ~2 Compared to the original sample, the corrosion rate decreased by approximately 240 times, and compared to the sample with only anodization, it decreased by approximately 30%. Based on Faraday's law, which states that the electrochemical corrosion rate increases linearly with corrosion current density, the lower the corrosion current density, the slower the corrosion rate of the alloy and the better its corrosion resistance. This indicates that the anodization + Al2O3 / La2O3 / silane coating prepared in Example 2 significantly improved the corrosion resistance of the TiB2-reinforced Al-based composite material.

[0057] The EIS results of the TiB2-reinforced Al-based composite materials with different surface treatments in this embodiment are shown in the figure. Figure 3 Among them, (a) Nyquist plot; (b) Bode plot, from Figure 3 As can be seen, the capacitance-reaction arc of the three samples gradually increases in the order of no surface treatment < anodizing only < anodizing + Al2O3 / La2O3 / silane coating. Generally, the larger the radius of the capacitance arc on the Nyquist plot, the better the corrosion resistance. The anodized + Al2O3 / La2O3 / silane coating sample has the largest capacitance-reaction arc radius, the thickest oxide film, and the best corrosion resistance. The Bode plot shows the impedance modulus |Z| of the sample. The impedance modulus |Z| at low frequencies is used to qualitatively judge the corrosion resistance of the surface oxide film. The larger the impedance modulus, the thicker the oxide film, and the better the corrosion resistance. The anodized + Al2O3 / La2O3 / silane coating has the largest measured impedance modulus |Z|, indicating the best corrosion resistance. Combining the results of the Nyquist and Bode plots, it can be seen that the anodized + Al2O3 / La2O3 / silane coating in this embodiment has the best corrosion resistance.

[0058] The SEM morphology and EDS composition of the Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in this embodiment are shown in the figure. Figure 4 ,from Figure 4It can be seen that the surface of the anodic oxidation + Al2O3 / La2O3 / silane coating sample is mainly composed of Al, O, La, Ti, Si, and C elements. The distribution of Al, O, and La elements highly overlaps, indicating the formation of Al2O3 and La2O3. Simultaneously, Al, O, and La elements also aggregate in the areas where Ti elements are concentrated, indicating the presence of Al2O3 and La2O3 on the TiB2 ceramic particles, meaning that Al2O3 and La2O3 are distributed throughout the entire surface of the sample. The presence of Si and C elements indicates the presence of silane.

[0059] Example 3: A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, the specific steps of which are as follows:

[0060] (1) The surface of the TiB2 reinforced Al-based composite material was pretreated to obtain the surface-pretreated TiB2 reinforced Al-based composite material. The surface pretreatment method was as follows: the surface of the TiB2 reinforced Al-based composite material was sanded with sandpaper, then added to a NaOH solution with a concentration of 2 mol / L, and alkali-immersed at a temperature of 85℃ for 60s. Then it was added to a hydrochloric acid-nitric acid mixed acid solution (the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution was 1 mol / L and the concentration of nitric acid was 5 mol / L) for activation treatment for 5 min. After being washed with deionized water, it was stored in anhydrous ethanol for later use.

[0061] (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode are immersed in electrolyte A (the distance between the anode electrode and the cathode electrode is 10 nm), and anodizing is performed for 15 min under a positive constant voltage of 60 V to obtain a porous Al2O3 ceramic coating on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contains 200 g / L sulfuric acid H2SO4, 20 g / L citric acid C6H8O7, 38 g / L aluminum sulfate Al(SO4), 10 g / L cerium sulfate Ce(SO4), 15 g / L glycerol, and deionized water as the solvent;

[0062] (3) Dissolve zinc nitrate Zn(NO3)2, aluminum nitrate Al(NO3)3, lanthanum nitrate La(NO3)3, and cysteine ​​(Cys) in deionized water to form a mixed solution. Heat the mixed solution to 95°C and keep it at that temperature for 8 hours. Adjust the pH of the system to 9.5 using NOH solution to obtain solution B. The mixed solution contains 15 g / L zinc nitrate Zn(NO3)2, 10 g / L aluminum nitrate Al(NO3)3, 2 g / L lanthanum nitrate La(NO3)3, and 10 g / L cysteine ​​(Cys).

[0063] (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to a deionized water-ethanol solution (the volume ratio of deionized water to ethanol is 1:1) and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 3.5 using nitric acid and ammonia. Hydrolyze the solution at 80°C for 36 hours to obtain silane solution C. The mixed solution contains 150 ml / L of γ-aminopropyltriethoxysilane and 4 g / L of lanthanum nitrate.

[0064] (5) Mix solution B and silane solution C evenly to obtain solution D; the silane solution C accounts for 35% of the volume of solution B;

[0065] (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface was placed in solution D and sealed. The temperature was raised to 150°C and kept at the temperature for 12 hours to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

[0066] (7) The polarization curve of the sample was detected at room temperature using a three-electrode system. The sample to be tested was used as the working electrode, the saturated calomel electrode was used as the reference electrode, the platinum sheet was used as the counter electrode, and 3.5 wt.% NaCl solution was used as the electrolyte. The voltage scan range was set to OCP±0.25V and the scan rate was 2mV / s.

[0067] The potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 3 are shown below. Figure 5 .from Figure 5 As can be seen from the above, compared with the original sample without surface treatment, the polarization curve of the sample after surface treatment in Example 3 shifted downward, indicating that the anodic oxide + Al2O3 / La2O3 / silane coating generated after surface treatment reduced the self-corrosion current density of the composite material and improved its corrosion resistance.

[0068] The Eco and icorr data of the TiB2-reinforced Al-based composite material in this embodiment are shown in Table 3.

[0069] Table 3. Eco and icorr data of the surface-treated TiB2-reinforced Al-based composite material in Example 3.

[0070] Corrosion voltage (V) Corrosion current density (μA·cm²) Untreated surface ~0.799 24.93 Anodizing + Al2O3 / La2O3 / silane coating ~0.749 1.216

[0071] Table 1 shows that the corrosion potentials of the untreated and surface-treated anodic oxide + Al2O3 / La2O3 / silane coatings obtained in Example 1 are ~0.799V and ~0.763V, respectively. The corrosion voltages of the three samples are not significantly different, but their corrosion currents differ considerably. The corrosion current density of the untreated sample is 24.93 μA·cm⁻¹. ~2The corrosion current density of the anodized Al2O3 / La2O3 / silane coating is 0.7336 μA·cm. ~2 Compared to the original sample, the corrosion rate decreased by approximately 30 times. Based on Faraday's law, which states that the electrochemical corrosion rate increases linearly with corrosion current density, the lower the corrosion current density, the slower the corrosion rate of the alloy and the better its corrosion resistance. This indicates that anodic oxidation combined with an Al₂O₃ / La₂O₃ / silane coating improves the corrosion resistance of TiB₂-reinforced Al-based composite materials. Figure 5 The polarization curve results correspond to these.

[0072] Example 4: A method for preparing a corrosion-resistant coating of TiB2-reinforced Al-based composite material, the specific steps of which are as follows:

[0073] (1) The surface of TiB2 reinforced Al-based composite material is pretreated to obtain surface-pretreated TiB2 reinforced Al-based composite material; the surface pretreatment method is as follows: the surface of TiB2 reinforced Al-based composite material is polished with sandpaper, then added to a NaOH solution with a concentration of 1.5, and alkali soaked at a temperature of 75℃ for 30s, then added to a hydrochloric acid-nitric acid mixed acid solution (the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution is 1mol / L and the concentration of nitric acid is 5mol / L) for activation treatment for 3min, and after being washed with deionized water, it is stored in anhydrous ethanol for later use;

[0074] (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode were immersed in electrolyte A (the distance between the anode electrode and the cathode electrode was 20 nm), and anodizing was performed for 20 min under a positive constant voltage of 20 V to obtain a porous Al2O3 ceramic coating on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contained 188 g / L H2SO4, 18 g / L C6H8O7, 5.5 g / L Al(SO4)3, 3 g / L Ce(SO4)2, and 10 g / L glycerol, and the solvent was deionized water;

[0075] (3) Dissolve zinc nitrate Zn(NO3)2, aluminum nitrate Al(NO3)3, lanthanum nitrate La(NO3)3, and cysteine ​​(Cys) in deionized water to form a mixed solution. Heat the mixed solution to 80°C and keep it at that temperature for 6 hours. Adjust the pH of the system to 10 using NOH solution to obtain solution B. The mixed solution contains 10 g / L zinc nitrate Zn(NO3)2, 8.8 g / L aluminum nitrate Al(NO3)3, 1.1 g / L lanthanum nitrate La(NO3)3, and 5 g / L cysteine ​​(Cys).

[0076] (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to a deionized water-ethanol solution (the volume ratio of deionized water to ethanol is 1:1) and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 4.5 using nitric acid and ammonia. Hydrolyze the solution at 50°C for 12 hours to obtain silane solution C. The mixed solution contains 100 ml / L of γ-aminopropyltriethoxysilane and 1.9 g / L of lanthanum nitrate.

[0077] (5) Mix solution B and silane solution C evenly to obtain solution D; the silane solution C accounts for 15% of the volume of solution B;

[0078] (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface was placed in solution D and sealed. The temperature was raised to 120°C and kept at the temperature for 6 hours to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

[0079] The polarization curve of the sample was detected at room temperature using a three-electrode system. The sample under test was used as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum sheet as the counter electrode. 3.5 wt.% NaCl solution was used as the electrolyte. The voltage scan range was set to OCP±0.25V and the scan rate was 2mV / s.

[0080] The potentiodynamic polarization curves of the anodic oxidation + Al2O3 / La2O3 / silane coating prepared on the surface of the TiB2-reinforced Al-based composite material in Example 4 are shown below. Figure 6 ;from Figure 6 As can be seen from the above, compared with the original sample without surface treatment, the polarization curve of the sample after surface treatment in Example 4 shifted downward, indicating that the anodic oxide + Al2O3 / La2O3 / silane coating generated after surface treatment reduced the self-corrosion current density of the composite material and improved its corrosion resistance.

[0081] The Ecor and icorr data of the TiB2-reinforced Al-based composite material in this embodiment are shown in Table 4.

[0082] Table 4. Ecor and icorr data of the surface-treated TiB2-reinforced Al-based composite material in Example 4.

[0083] Corrosion voltage (V) Corrosion current density (μA·cm²) Untreated surface ~0.799 24.93 Anodizing + Al2O3 / La2O3 / silane coating ~0.790 0.3118

[0084] Table 4 shows that the corrosion potentials of the untreated and surface-treated anodic oxide + Al2O3 / La2O3 / silane coatings obtained in Example 4 are ~0.799V and ~0.790V, respectively. The corrosion voltages of the samples are not significantly different, but their corrosion currents differ considerably. The corrosion current density of the untreated sample is 24.93 μA·cm⁻¹. ~2The corrosion current density of the anodic oxidation + Al2O3 / La2O3 / silane coating is 0.3118 μA·cm. ~2 Compared to the original sample, the corrosion rate decreased by approximately 80 times. Based on Faraday's law, which states that the electrochemical corrosion rate increases linearly with corrosion current density, the lower the corrosion current density, the slower the corrosion rate of the alloy and the better its corrosion resistance. This indicates that anodic oxidation combined with an Al₂O₃ / La₂O₃ / silane coating improves the corrosion resistance of TiB₂-reinforced Al-based composite materials. Figure 6 The polarization curve results correspond to these.

[0085] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a corrosion-resistant coating of a TiB2-reinforced Al-based composite material, characterized in that, The specific steps are as follows: (1) The surface of TiB2 reinforced Al-based composite material was pretreated to obtain surface-pretreated TiB2 reinforced Al-based composite material; (2) Using a surface-pretreated TiB2-reinforced Al-based composite material as the anode electrode and a lead plate as the cathode electrode, the anode electrode and the cathode electrode are immersed in electrolyte A for anodic oxidation to obtain a porous Al2O3 ceramic coating on the surface of the TiB2-reinforced Al-based composite material; the electrolyte A contains 150~200g / L H2SO4, 10~20g / L C6H8O7, 1~8g / L Al2(SO4)3, 1~10g / L Ce(SO4)2, 5~15g / L glycerol, and deionized water as the solvent; (3) Dissolve zinc nitrate, aluminum nitrate, lanthanum nitrate, and cysteine ​​in deionized water to form a mixed solution. Heat the mixed solution to 60-95°C and keep it at that temperature for 1-8 hours. Adjust the pH of the system to 9.5-10.5 to obtain solution B. The mixed solution contains 8-15 g / L zinc nitrate, 1-10 g / L aluminum nitrate, 0.5-2 g / L lanthanum nitrate, and 1-10 g / L cysteine. (4) Add γ-aminopropyltriethoxysilane and lanthanum nitrate sequentially to a deionized water-ethanol solution and stir to obtain a mixed solution. Adjust the pH of the mixed solution to 3.5-4.5 with nitric acid and ammonia. Hydrolyze the solution at 25-90℃ for 24-48h to obtain silane solution C. The mixed solution contains 50-150 ml / L of γ-aminopropyltriethoxysilane and 1-4 g / L of lanthanum nitrate. (5) Mix solution B and silane solution C evenly to obtain solution D; the silane solution C accounts for 5~40% of the volume of solution B; (6) The TiB2 reinforced Al-based composite material with a porous Al2O3 ceramic coating on the surface is placed in solution D and sealed. The temperature is raised to 110~150℃ and kept at the temperature for 6~12h to co-deposit an Al2O3 / La2O3 / silane coating on the surface of the TiB2 reinforced Al-based composite material.

2. The method for preparing the corrosion-resistant coating of the TiB2-reinforced Al-based composite material according to claim 1, characterized in that: The surface pretreatment method in step (1) is as follows: the surface of TiB2 reinforced Al-based composite material is sanded with sandpaper, then added to NaOH solution, and alkali soaked at 60~85℃ for 5~60s. Then it is added to hydrochloric acid-nitric acid mixed acid solution for activation treatment for 1~5min. After being washed with deionized water, it is stored in anhydrous ethanol for later use.

3. The method for preparing the corrosion-resistant coating of the TiB2-reinforced Al-based composite material according to claim 2, characterized in that: The concentration of NaOH solution is 0.5~2 mol / L, and the concentration of hydrochloric acid in the hydrochloric acid-nitric acid mixed acid solution is 0.5~1.5 mol / L, and the concentration of nitric acid is 3~6 mol / L.

4. The method for preparing the corrosion-resistant coating of the TiB2-reinforced Al-based composite material according to claim 1, characterized in that: The distance between the anode and cathode electrodes is 5~10nm, the forward constant voltage for anodizing is 10~60V, and the anodizing time is 10~60min.

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