High-temperature-resistant anodic oxide film layer and preparation method thereof

Abstract

The invention relates to the technical field of metal surface treatment, in particular to a high-temperature-resistant anodic oxide film layer and a preparation method thereof.The preparation method comprises the following steps that S1, an aluminum alloy base material is soaked in pretreatment working fluid to obtain a pretreated base material; s2, the pretreated base material serves as an anode, direct-current constant-current anodic oxidation is conducted in electrolyte, and an anodic oxidation base material is obtained; s3, the anodic oxidation base material is immersed in hole sealing liquid for hole sealing treatment, and a hole sealing base material is obtained; and S4, the hole sealing base material is heated and subjected to heat preservation in the air atmosphere, and after cooling, the high-temperature-resistant anodic oxide film is obtained. The anodic oxide film layer with excellent high temperature resistance, thermal shock resistance and salt spray corrosion resistance is prepared by selecting the components of the pretreatment working solution and optimizing the technological parameters of anodic oxidation and hole sealing treatment.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a high-temperature resistant anodic oxide film and its preparation method. Background Technology

[0002] Anodizing is a surface treatment process that forms an oxide film on a metal surface through electrochemical methods, particularly suitable for aluminum and aluminum alloys. Since its development, this technology has become an important means of improving the corrosion resistance, wear resistance, and decorative properties of metal parts. Its basic principle is to use aluminum or its alloy as the anode, applying direct current in a specific electrolyte environment to cause an oxidation reaction on the material surface, thereby generating a dense aluminum oxide film of a certain thickness. This film bonds firmly to the substrate, possesses good chemical stability and mechanical properties, and can effectively extend the service life of components in harsh environments. It is widely used in many fields such as semiconductors, aerospace, automotive manufacturing, electronics, building materials, and daily consumer goods.

[0003] In existing technologies, the coefficients of thermal expansion of anodic oxide films differ significantly from those of the metal substrate. Drastic temperature changes or cycling can lead to microcracks in the film or even its peeling off from the substrate, drastically reducing its protective function and exposing the base metal to rapid oxidation and corrosion at high temperatures. Furthermore, anodic oxide films are primarily composed of amorphous alumina, which is unstable at high temperatures. Prolonged exposure to high temperatures causes a phase transition from amorphous to crystalline states. This process is accompanied by volume shrinkage and structural changes, resulting in a porous and embrittled film with increased porosity, significantly reducing its corrosion resistance and mechanical strength. Summary of the Invention

[0004] To address the problems mentioned in the background section, this invention provides a high-temperature resistant anodic oxide film and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0007] S1. Immerse the aluminum alloy substrate in the pretreatment working solution for 1-5 minutes, then rinse it to obtain the pretreated substrate.

[0008] S2. Using the previously treated substrate as the anode, perform DC constant current anodizing in the electrolyte for 60-80 minutes to obtain the anodized substrate;

[0009] S3. Immerse the anodized substrate in the sealing solution for 40-60 minutes to seal the pores and obtain the sealed substrate.

[0010] S4. Heat and keep the sealing substrate in air for 1-2 hours, and after cooling, obtain a high-temperature resistant anodized film.

[0011] Furthermore, the pretreatment working solution in step S1 is prepared by the following steps:

[0012] 2-Vinylpyridine and styrylboronic acid were added to a reactor pre-filled with N,N-dimethylformamide. Under nitrogen protection, azobisisobutyronitrile was added, the system was heated, and the reaction was stirred in the dark for 12-18 hours. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.0-1.5 g / L and a pH of 6.5-6.8 using deionized water.

[0013] Furthermore, the molar ratio of 2-vinylpyridine, styrylboronic acid and azobisisobutyronitrile is 1:(0.8-1.2):(0.01-0.05), and the mass ratio is 1:(1.12-1.68):(0.015-0.078).

[0014] Furthermore, the temperature is raised to 70-80℃, and the stirring speed is 100-200 rpm.

[0015] Furthermore, in step S2, the electrolyte is a mixed aqueous solution of sulfuric acid and cerium sulfate, wherein the concentration of sulfuric acid is 160-200 g / L and the concentration of cerium sulfate is 5-10 g / L.

[0016] Furthermore, the process conditions for anodic oxidation in step S2 are as follows: the electrolyte temperature is maintained at (-2)-2℃, and the current density is 2.0-3.0A / dm².

[0017] Furthermore, in step S3, the sealing solution is a mixed aqueous solution of cerium acetate and hydrogen peroxide, wherein the concentration of cerium acetate is 5-10 g / L, the concentration of hydrogen peroxide is 5-10 mL / L, and the pH value of the sealing solution is 4.5-5.5.

[0018] Furthermore, the sealing temperature in step S3 is 90-100℃.

[0019] Furthermore, in step S4, the heating rate is 1-3℃ / min, and the target temperature is 100-120℃.

[0020] According to another aspect of the present invention, a high-temperature resistant anodic oxide film layer prepared by the above preparation method is provided.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention utilizes a pretreatment process to construct a stronger interfacial transition layer between the aluminum substrate and the oxide film. The pretreatment process employs a copolymer containing styrene-boronic acid, whose boric acid groups react with the hydroxyl groups on the aluminum substrate surface to form BO-Al covalent bonds. Simultaneously, other functional groups in the copolymer also contribute to enhancing interfacial interactions. This transition layer structure helps alleviate internal stress caused by the mismatch in thermal expansion coefficients between the metal and ceramic, thereby potentially reducing the tendency for the film to crack or peel during thermal cycling, and improving the structural integrity and service reliability of the film under high-temperature conditions.

[0023] 2. By introducing functional components and regulating the heat treatment process, the phase transformation behavior of alumina was positively affected. This helped to suppress the excessively rapid growth of grains at high temperatures and promote the formation of a more stable crystal structure. At the same time, some components can be transformed into a fluid phase at high temperatures, which can fill and heal microcracks caused by the volume change of the phase transformation to a certain extent. This helps to reduce the risk of high-temperature pulverization of the film and enable it to maintain relatively stable performance in high-temperature environments. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides a method for preparing a high-temperature resistant anodized film, preferably comprising the following steps:

[0026] S1. Immerse the aluminum alloy substrate in the pretreatment working solution for 1-5 minutes, then rinse it to obtain the pretreated substrate.

[0027] S2. Using the previously treated substrate as the anode, perform DC constant current anodizing in the electrolyte for 60-80 minutes to obtain the anodized substrate;

[0028] S3. Immerse the anodized substrate in the sealing solution for 40-60 minutes to seal the pores and obtain the sealed substrate.

[0029] S4. Heat and keep the sealing substrate in air for 1-2 hours, and after cooling, obtain a high-temperature resistant anodized film.

[0030] In the preparation method provided by the present invention, the pretreatment working solution in step S1 is prepared by the following steps:

[0031] 2-Vinylpyridine and styrylboronic acid were added to a reactor pre-filled with N,N-dimethylformamide. Under nitrogen protection, azobisisobutyronitrile was added, the system was heated, and the reaction was stirred in the dark for 12-18 hours. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.0-1.5 g / L and a pH of 6.5-6.8 using deionized water.

[0032] In the preparation method provided by this invention, the preferred mass ratio of 2-vinylpyridine, styrylboronic acid, and azobisisobutyronitrile is 1:(1.12-1.68):(0.015-0.078), specifically (1:1.12:0.015), (1:1.15:0.022), (1:1.18:0.025), (1:1.20:0.036), (1:1.21:0.038), (1:1.25:0.040), ( 1:1.29:0.042), (1:1.30:0.045), (1:1.35:0.052), (1:1.32:0.055), (1:1.39:0.058), (1:1.40:0.066), (1:1.48:0.068), (1:1.50:0.069), (1:1.55:0.070), (1:1.63:0.075) and (1:1.68:0.078).

[0033] In the preparation method provided by the present invention, the preferred heating temperature is 70-80℃, specifically 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃ and 80℃.

[0034] In the preparation method provided by the present invention, the stirring speed is preferably 100-200 rpm, specifically 100 rpm, 150 rpm and 200 rpm.

[0035] In the preparation method provided by the present invention, the electrolyte in step S2 is a mixed aqueous solution of sulfuric acid and cerium sulfate. The concentration of sulfuric acid is preferably 160-200 g / L, specifically 160 g / L, 170 g / L, 175 g / L, 180 g / L, 190 g / L and 200 g / L; the concentration of cerium sulfate is preferably 5-10 g / L, specifically 5 g / L, 6 g / L, 7 g / L, 8 g / L, 8.5 g / L, 9 g / L and 10 g / L.

[0036] In the preparation method provided by the present invention, the process conditions for anodic oxidation in step S2 are as follows: the electrolyte temperature is preferably (-2)-2℃, specifically -2℃, -1℃, 0℃, 1℃ and 2℃; the current density is preferably 2.0-3.0A / dm², specifically 2.0A / dm², 2.1A / dm², 2.2A / dm², 2.3A / dm², 2.4A / dm², 2.5A / dm², 2.6A / dm², 2.7A / dm², 2.8A / dm², 2.9A / dm² and 3.0A / dm².

[0037] In the preparation method provided by the present invention, the sealing solution in step S3 is a mixed aqueous solution of cerium acetate and hydrogen peroxide. The concentration of cerium acetate is preferably 5-10 g / L, specifically 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L and 10 g / L; the concentration of hydrogen peroxide is preferably 5-10 mL / L, specifically 5 mL / L, 6 mL / L, 7 mL / L, 8 mL / L, 9 mL / L and 10 mL / L; the pH value of the sealing solution is preferably 4.5-5.5, specifically 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 and 5.5.

[0038] In the preparation method provided by the present invention, the temperature of the sealing treatment in step S3 is preferably 90-100℃, specifically 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, 99℃ and 100℃.

[0039] In the preparation method provided by the present invention, the heating rate in step S4 is preferably 1-3℃ / min, specifically 1℃ / min, 2℃ / min and 3℃ / min; the target temperature is preferably 100-120℃, specifically 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 112℃, 115℃ and 120℃.

[0040] For clarity, the following examples and comparative examples provide a detailed description. The aluminum alloy substrate used in the following examples and comparative examples is AA2024 aluminum alloy.

[0041] Example 1 The pretreatment working solution is prepared by the following steps:

[0042] 10 g of 2-vinylpyridine and 11.2 g of styrylboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.15 g of azobisisobutyronitrile was added. The system was heated to 70 °C and stirred at 100 rpm for 12 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.0 g / L and a pH of 6.5 using deionized water.

[0043] Example 2 The pretreatment working solution is prepared by the following steps:

[0044] 10 g of 2-vinylpyridine and 12.9 g of styreneboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.42 g of azobisisobutyronitrile was added. The system was heated to 72 °C and stirred at 150 rpm for 14 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.1 g / L and a pH of 6.6 using deionized water.

[0045] Example 3 The pretreatment working solution is prepared by the following steps:

[0046] 10 g of 2-vinylpyridine and 13.5 g of styreneboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.52 g of azobisisobutyronitrile was added. The system was heated to 74 °C and stirred at 150 rpm for 15 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.2 g / L and a pH of 6.6 using deionized water.

[0047] Example 4 The pretreatment working solution is prepared by the following steps:

[0048] 10 g of 2-vinylpyridine and 14.0 g of styrylboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.66 g of azobisisobutyronitrile was added. The system was heated to 75 °C and stirred at 150 rpm for 16 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.3 g / L and a pH of 6.7 using deionized water.

[0049] Example 5 The pretreatment working solution is prepared by the following steps:

[0050] 10 g of 2-vinylpyridine and 15.5 g of styreneboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.70 g of azobisisobutyronitrile was added. The system was heated to 78 °C and stirred at 150 rpm for 16 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.4 g / L and a pH of 6.8 using deionized water.

[0051] Example 6 The pretreatment working solution is prepared by the following steps:

[0052] 10 g of 2-vinylpyridine and 16.8 g of styrylboronic acid were added to a reactor pre-filled with 100 mL of N,N-dimethylformamide. Under nitrogen protection, 0.78 g of azobisisobutyronitrile was added. The system was heated to 80 °C and stirred at 200 rpm for 18 h in the dark. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.5 g / L and a pH of 6.8 using deionized water.

[0053] Example 7 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0054] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 1 for 1 minute, then take it out and rinse it to obtain the pretreated substrate.

[0055] S2. Using the previously treated substrate as the anode, the substrate is subjected to DC constant current anodizing at (-2)℃ in an electrolyte containing 160 g / L sulfuric acid and 5 g / L cerium sulfate for 60 min at a current density of 2.0 A / dm² to obtain an anodized substrate.

[0056] S3. Immerse the anodized substrate in a sealing solution containing 5 g / L cerium acetate and 5 mL / L hydrogen peroxide with a pH of 4.5, and seal the substrate at 90°C for 40 min to obtain a sealed substrate.

[0057] S4. The sealing substrate is heated to 100°C in air at a heating rate of 1°C / min and held at that temperature for 1 hour. After cooling, a high-temperature resistant anodized film is obtained.

[0058] Example 8 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0059] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 2 for 2 minutes, then take it out and rinse it to obtain the pretreated substrate.

[0060] S2. Using the previously treated substrate as the anode, the substrate is subjected to DC constant current anodizing at a current density of 2.1 A / dm² for 70 min in an electrolyte containing 170 g / L sulfuric acid and 6 g / L cerium sulfate at (-1) °C to obtain an anodized substrate.

[0061] S3. Immerse the anodized substrate in a sealing solution containing 6 g / L cerium acetate and 6 mL / L hydrogen peroxide with a pH of 4.7, and seal the substrate at 92°C for 45 min to obtain a sealed substrate.

[0062] S4. The sealing substrate is heated to 102°C in air at a heating rate of 2°C / min and held at that temperature for 1 hour. After cooling, a high-temperature resistant anodized film is obtained.

[0063] Example 9 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0064] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 3 for 3 minutes, then take it out and rinse it to obtain the pretreated substrate.

[0065] S2. Using the previously treated substrate as the anode, perform DC constant current anodizing at 0°C in an electrolyte containing 175 g / L sulfuric acid and 7 g / L cerium sulfate for 70 min at a current density of 2.2 A / dm² to obtain an anodized substrate;

[0066] S3. Immerse the anodized substrate in a sealing solution containing 7 g / L cerium acetate and 6 mL / L hydrogen peroxide with a pH of 4.8, and seal the substrate at 93°C for 50 min to obtain a sealed substrate.

[0067] S4. The sealing substrate is heated to 105°C in air at a heating rate of 3°C / min and held at that temperature for 2 hours. After cooling, a high-temperature resistant anodized film is obtained.

[0068] Example 10 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0069] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 4 for 4 minutes, then take it out and rinse it to obtain the pretreated substrate.

[0070] S2. Using the previously treated substrate as the anode, perform DC constant current anodizing at 2.5 A / dm² for 70 min in an electrolyte containing 180 g / L sulfuric acid and 8 g / L cerium sulfate at 1 °C to obtain an anodized substrate.

[0071] S3. Immerse the anodized substrate in a sealing solution containing 8 g / L cerium acetate and 7 mL / L hydrogen peroxide with a pH of 5.0, and seal the substrate at 95°C for 55 min to obtain a sealed substrate.

[0072] S4. The sealing substrate is heated to 108°C in air at a heating rate of 1°C / min and held at that temperature for 2 hours. After cooling, a high-temperature resistant anodized film is obtained.

[0073] Example 11 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0074] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 5 for 4 minutes, then take it out and rinse it to obtain the pretreated substrate.

[0075] S2. Using the previously treated substrate as the anode, anodize the substrate by DC constant current for 80 min at a current density of 2.8 A / dm² in an electrolyte containing 190 g / L sulfuric acid and 9 g / L cerium sulfate at 1 °C to obtain an anodized substrate.

[0076] S3. Immerse the anodized substrate in a sealing solution containing 9 g / L cerium acetate and 9 mL / L hydrogen peroxide with a pH of 5.3, and seal the substrate at 98°C for 60 min to obtain a sealed substrate.

[0077] S4. The sealing substrate is heated to 110°C in air at a heating rate of 2°C / min and held at that temperature for 2 hours. After cooling, a high-temperature resistant anodized film is obtained.

[0078] Example 12 A method for preparing a high-temperature resistant anodic oxide film includes the following steps:

[0079] S1. Immerse the degreased aluminum alloy substrate in the pretreatment working solution prepared in Example 6 for 5 minutes, then take it out and rinse it to obtain the pretreated substrate.

[0080] S2. Using the previously treated substrate as the anode, anodize the substrate by DC constant current for 80 min at a current density of 3.0 A / dm² in an electrolyte containing 200 g / L sulfuric acid and 10 g / L cerium sulfate at 2 °C to obtain an anodized substrate.

[0081] S3. Immerse the anodized substrate in a sealing solution containing 10 g / L cerium acetate and 10 mL / L hydrogen peroxide with a pH of 5.5, and seal the substrate at 100°C for 60 min to obtain a sealed substrate.

[0082] S4. The sealing substrate is heated to 120°C in air at a heating rate of 3°C / min and held at that temperature for 2 hours. After cooling, a high-temperature resistant anodized film is obtained.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that 2-vinylpyridine is not added; the remaining steps are the same as in Example 1.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 2 is that styrene-boronic acid is not added; the remaining steps are the same as in Example 2.

[0087] Comparative Example 3

[0088] The difference between this comparative example and Example 7 is that N,N-dimethylformamide is used as the pretreatment working solution, while the remaining steps are the same as in Example 7.

[0089] Comparative Example 4

[0090] The difference between this comparative example and Example 8 is that the pretreatment working solution was prepared using Comparative Example 1 in step S1, while the remaining steps are the same as in Example 8.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 9 is that the pretreatment working solution was prepared using Comparative Example 2 in step S1, while the remaining steps are the same as in Example 9.

[0093] Comparative Example 6

[0094] The difference between this comparative example and Example 10 is that step S1 is omitted, while the remaining steps are the same as in Example 10.

[0095] Comparative Example 7

[0096] The difference between this comparative example and Example 11 is that step S3 is omitted, while the remaining steps are the same as in Example 11.

[0097] Take the samples prepared in Examples 7-12 and Comparative Examples 1-7, clean and dry them to constant weight, record the initial mass m0 (unit: mg) and the total surface area A (unit: cm²) of each sample, place them in a muffle furnace, heat to 450℃, hold for 2 hours, cool to room temperature, remove the samples, place them in a desiccator, let them stand for 1 hour, and record the mass (m1) of each sample again. Calculate the mass change Δm1 of the high-temperature exposure test using the following formula:

[0098] Δm1=(m1-m 0) / A

[0099] Take another set of new parallel samples that have not been exposed to high temperatures. Place the samples in a muffle furnace, heat to 250°C, hold for 15 minutes, then quickly immerse the samples in a 25°C water bath, ensuring complete immersion, and quench for 10 minutes to complete one cycle. Remove the samples from the water bath, blot dry the surface moisture, and immediately place them back into the 250°C muffle furnace to begin the next cycle. Repeat the above steps until 20 cycles are completed. After the 20th cycle, remove the samples from the water bath, blot dry the surface moisture, and then dry them in a 50°C oven for 1 hour, then cool to room temperature. Record the final mass m2 (unit: mg) of each sample, and calculate the mass change Δm2 of the thermal shock test using the following formula:

[0100] Δm2=(m2-m 0) / A

[0101] The results are shown in Table 1:

[0102] Table 1. Results of sample mass changes after high-temperature exposure and thermal shock tests

[0103] Group <![CDATA[Δm1(mg / cm²)]]> <![CDATA[Δm2(mg / cm²)]]> Example 7 -0.82 -1.95 Example 8 -0.68 -1.73 Example 9 -0.51 -1.35 Example 10 -0.52 -1.48 Example 11 -0.48 -1.38 Example 12 -0.45 -1.32 Comparative Example 1 -3.85 -8.92 Comparative Example 2 -4.12 -9.35 Comparative Example 3 -6.53 -14.24 Comparative Example 4 -3.59 -9.01 Comparative Example 5 -4.28 -9.64 Comparative Example 6 -7.25 -16.50 Comparative Example 7 -5.78 -7.21

[0104] A neutral salt spray test was conducted according to ASTM B117, "Salt Spray Test Standard." Samples from Examples 7-12 and Comparative Examples 1-7, which had undergone the aforementioned high-temperature exposure test (450°C, 2 hours) and cooled to room temperature, were gently wiped with a soft cloth or absorbent cotton soaked in anhydrous ethanol and allowed to air dry. Sodium chloride was dissolved in deionized water to prepare a 5% (mass percentage) salt solution. Deionized water was poured into the bottom of the salt spray chamber, and the prepared salt solution was poured into the storage tank. The parameters were set as follows: chamber temperature 35°C, saturation tower temperature 47°C.

[0105] Place the prepared samples on the sample holder at a 30° angle. Sufficient distance should be maintained between samples and between samples and the chamber walls to ensure that the salt spray can freely settle on all sample surfaces and that condensate does not drip from one sample to another.

[0106] After the test began, the test was briefly interrupted every 24 hours. The chamber lid was opened, and the sample was quickly removed to observe whether white or grayish-white corrosion products (white rust) appeared on the surface. The time point t (in hours) when corrosion spots appeared was recorded. After the inspection, the sample was quickly returned to its original position in the chamber, and the test continued. The test was terminated after 240 hours. The protection level of the sample surface was evaluated according to ISO 10289, "Rating of test specimens and parts subjected to corrosion tests on metallic and other inorganic coatings on metallic parts". The results are shown in Table 2:

[0107] Table 2. Results of Neutral Salt Spray Test

[0108] Group Time t (h) for white rust to appear Protection level (Rρ) Example 7 216 8 Example 8 216 8 Example 9 216 8 Example 10 216 8 Example 11 ＞240 9 Example 12 ＞240 9 Comparative Example 1 48 3 Comparative Example 2 48 3 Comparative Example 3 24 1 Comparative Example 4 48 3 Comparative Example 5 48 3 Comparative Example 6 24 1 Comparative Example 7 72 5

[0109] As shown in Table 1, the absolute values ​​of mass changes Δm1 and Δm2 in Examples 7-12 were relatively small in the high-temperature exposure test and thermal shock test. This indicates that the high-temperature resistant anodized films prepared in the examples have good stability under high-temperature conditions, with less mass loss, and the film layer can effectively protect the aluminum alloy substrate and reduce its corrosion by high temperature.

[0110] Comparative Examples 1-2, without the addition of 2-vinylpyridine and styrylboronic acid, showed a significant increase in the absolute values ​​of mass changes Δm1 and Δm2 compared to the examples. This indicates that 2-vinylpyridine and styrylboronic acid play a crucial role in the preparation of the pretreatment working solution, possibly participating in the reaction to form polymers with special structures and properties, which helps improve the high-temperature resistance and thermal shock resistance of the membrane. The absence of either component significantly degrades the membrane performance. Comparative Example 3, using N,N-dimethylformamide as the pretreatment working solution, showed the most significant mass change, with absolute values ​​of Δm1 and Δm2 much larger than those in the examples. This indicates that using only the solvent N,N-dimethylformamide cannot form an effective protective membrane, while the pretreatment working solution generated by the reaction of components such as 2-vinylpyridine and styrylboronic acid in the examples can significantly improve the membrane performance and enhance its high-temperature resistance and thermal shock resistance. Comparative Examples 4-5, using the pretreatment working solutions prepared in Comparative Examples 1 and 2, showed similar results to Comparative Examples 1-2, with large mass changes. In Comparative Example 6, without the pretreatment step S1, the absolute values ​​of the mass changes Δm1 and Δm2 are also large. This indicates that the pretreatment step is crucial for improving film performance, as it can form an interface layer on the aluminum alloy substrate surface that is beneficial for subsequent anodizing and sealing processes, enhancing the adhesion between the film and the substrate, thereby improving the film's high-temperature resistance and thermal shock resistance.

[0111] In Comparative Example 7, without the sealing treatment in step S3, the absolute value of the mass change Δm1 is relatively small, but the absolute value of Δm2 is relatively large. This indicates that the sealing treatment plays an important role in improving the thermal shock resistance of the film. The components in the sealing solution can fill the pores of the anodic oxide film, reducing film cracking and peeling caused by thermal stress during thermal shock, thereby reducing mass loss.

[0112] As shown in Table 2, in the neutral salt spray test, Examples 7-12 showed a later onset of white rust and a higher level of protection. This indicates that the high-temperature resistant anodic oxide film prepared in these examples has excellent salt spray corrosion resistance, effectively preventing the corrosion of aluminum alloy substrates by corrosive media such as chloride ions in the salt spray, and extending the service life of the substrate in the salt spray environment.

[0113] In summary, by selecting the components of the pretreatment working solution and optimizing the process parameters of anodic oxidation and sealing, an anodic oxide film with excellent high-temperature resistance, thermal shock resistance, and salt spray corrosion resistance was prepared in the embodiments.

[0114] In the description of this specification, the terms "preparation example," "example," "various examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that example or preparation example, which are included in at least one example or preparation example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same example or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more examples or preparation examples.

[0115] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant anodic oxide film, characterized in that, Includes the following steps: S1. Immerse the aluminum alloy substrate in the pretreatment working solution for 1-5 minutes, then rinse it to obtain the pretreated substrate. S2. Using the previously treated substrate as the anode, perform DC constant current anodizing in the electrolyte for 60-80 minutes to obtain the anodized substrate; S3. Immerse the anodized substrate in the sealing solution for 40-60 minutes to seal the pores and obtain the sealed substrate. S4. Heat and keep the sealing substrate in air for 1-2 hours, and after cooling, obtain a high-temperature resistant anodized film; The pretreatment working solution in step S1 is prepared by the following steps: 2-Vinylpyridine and styrylboronic acid were added to a reactor pre-filled with N,N-dimethylformamide. Under nitrogen protection, azobisisobutyronitrile was added, the system was heated, and the reaction was stirred in the dark for 12-18 hours. The solid was collected and prepared into a pretreatment working solution with a concentration of 1.0-1.5 g / L and a pH of 6.5-6.8 using deionized water.

2. The preparation method according to claim 1, characterized in that, The mass ratio of 2-vinylpyridine, styrylboronic acid, and azobisisobutyronitrile is 1:(1.12-1.68):(0.015-0.078).

3. The preparation method according to claim 1, characterized in that, The temperature is raised to 70-80℃, and the stirring speed is 100-200 rpm.

4. The preparation method according to claim 1, characterized in that, In step S2, the electrolyte is a mixed aqueous solution of sulfuric acid and cerium sulfate, wherein the concentration of sulfuric acid is 160-200 g / L and the concentration of cerium sulfate is 5-10 g / L.

5. The preparation method according to claim 1, characterized in that, The process conditions for anodic oxidation in step S2 are: the electrolyte temperature is maintained at (-2)-2℃, and the current density is 2.0-3.0A / dm².

6. The preparation method according to claim 1, characterized in that, In step S3, the sealing solution is a mixed aqueous solution of cerium acetate and hydrogen peroxide, wherein the concentration of cerium acetate is 5-10 g / L, the concentration of hydrogen peroxide is 5-10 mL / L, and the pH value of the sealing solution is 4.5-5.

5.

7. The preparation method according to claim 1, characterized in that, The sealing temperature in step S3 is 90-100℃.

8. The preparation method according to claim 1, characterized in that, The heating rate in step S4 is 1-3℃ / min, and the target temperature is 100-120℃.

9. A high-temperature resistant anodic oxide film layer prepared by the preparation method according to any one of claims 1-8.