Aluminum alloy anodizing film sealing agent with sealing and hydrophobic functions and application thereof

Abstract

The present application relates to the technical field of aluminum and aluminum alloy anodic oxidation film surface treatment, and discloses an aluminum alloy anodic oxidation film sealing agent with sealing and hydrophobic functions and application thereof, which is composed of the following components: magnesium acetate, ammonia organic acid, ammonia surfactant, corrosion inhibitor, pH buffer and water. The present application uses magnesium acetate as the main sealing material, and ammonia organic acid and ammonia surfactant are used in synergistic action to realize efficient sealing of the anodic oxidation film and simultaneously build a hydrophobic surface, and the obtained film layer has a water drop angle of > 110°. The sealing agent uses water as the solvent, does not contain volatile organic compounds (VOC), heavy metal ions and toxic and harmful substances such as formaldehyde, has long-term hydrophobicity and excellent corrosion resistance, is environmentally friendly and harmless, has low cost, and is simple to operate, and is suitable for protective treatment of aluminum alloy anodic oxidation film.

Description

Technical Field

[0001] This invention relates to the field of aluminum and aluminum alloy anodic oxide film surface treatment technology, and in particular to an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions and its application. Background Technology

[0002] Aluminum alloys possess advantages such as low density, high specific strength, and good electrical conductivity, making them the most produced and widely used lightweight metal structural material. They are extensively used in aerospace, construction, shipbuilding, and electronic equipment. To improve the corrosion resistance of aluminum alloys, anodizing is commonly used in industry to form a stable anodic oxide film on the surface. To inhibit the formation of electrochemical corrosion microcells in the natural environment and avoid localized corrosion and performance degradation, the surface is usually hydrophobically modified to increase the water contact angle to over 90°. Hydrophobic surfaces can significantly reduce liquid retention, thereby lowering the probability of microcell corrosion.

[0003] In actual production, anodic oxide films need to be sealed to reduce film adsorption and improve their anti-pollution, corrosion resistance, and electrical insulation. Currently, the mainstream sealing technologies in industry are boiling water sealing and nickel salt sealing. Boiling water sealing easily causes surface dusting, reduces hardness, and worsens wear and impact resistance in aluminum materials. Nickel-containing sealing agents face significant environmental pressure due to restrictions on nickel ion emissions, high wastewater treatment costs, and the fact that nickel-containing waste is hazardous. Therefore, developing nickel-free and fluorine-free environmentally friendly sealing processes has become a research hotspot in the field of aluminum alloy surface treatment. Existing nickel-free sealing technologies generally have performance shortcomings: processes with excellent corrosion resistance (such as silicate sealing) often have poor appearance; processes with good decorative properties (such as alkali metal salt sealing) generally have poor salt spray resistance; and rare earth and organic composite systems suffer from insufficient sealing quality and poor corrosion resistance.

[0004] CN115142055A discloses a hydrophobic chemical conversion film using a compound of trivalent chromium salts, fluorozirconates, and fluorotitanic acid / fluorotitanic acid, achieving a contact angle of approximately 103° for the aluminum alloy oxide film composite coating, with slightly improved corrosion resistance. CN118547355A discloses a highly wear-resistant, superhydrophobic composite film layer for aluminum alloy surfaces, prepared using anhydrous ethanol, ammonia, and perfluoroalkyl silanes, achieving a contact angle of approximately 150°. CN106400079A discloses a method for preparing a multilayer superhydrophobic composite film layer on an aluminum alloy surface, using a stearic acid-ethanol solution for low surface energy modification, resulting in a contact angle greater than 150°.

[0005] However, the aforementioned hydrophobic modification systems mostly employ fluorinated organic compounds, volatile organic solvents, and trivalent chromium compounds, posing environmental and health risks in terms of VOC emissions, safety of use, biocompatibility, and waste liquid and residue treatment. Therefore, developing an environmentally friendly, nickel-free, and fluorine-free sealing agent for aluminum alloy anodic oxide films that also possesses dual functions of sealing and hydrophobicity is of significant research value and engineering application importance. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions and its application. The aim is to achieve nickel-free and fluorine-free environmentally friendly sealing, while taking into account the sealing quality of the oxide film and the surface hydrophobic properties, giving the anodic oxide film long-lasting hydrophobic properties, and significantly improving the overall corrosion resistance of aluminum and aluminum alloys.

[0007] To achieve this objective, the present invention adopts the following technical solution: This invention first discloses a sealing agent for aluminum alloy anodic oxide films that combines sealing and hydrophobic functions, composed of the following components at the following mass concentrations: Magnesium acetate 1~7g / L; Ammonia-based organic acids: 0.5~5 g / L; Ammonia-based surfactants: 0.1~1 g / L; Corrosion inhibitor 0.01~0.2g / L; pH buffer 0.5~2g / L; The remainder is deionized water.

[0008] The sealing agent of the present invention uses magnesium acetate as the main sealing salt, which works synergistically with ammonia organic acids and ammonia surfactants to form a dense hydrophobic composite film on the surface of aluminum and aluminum alloy anodic oxide films, thereby significantly improving their corrosion resistance.

[0009] As a preferred embodiment, the amino acid is any one or a mixture of at least two of glutamic acid, aspartic acid, histidine, and phenylalanine. This type of organic acid can react with Al. 3+ Mg 2+ Complexation occurs, promoting the formation of sealing membranes; excessively high concentrations of ammonia-based organic acids can accelerate the dissolution of alumina films, causing damage to the oxide films.

[0010] As a preferred embodiment, the ammonia-based surfactant is any one or a mixture of at least two of sodium lauroyl sarcosinate, sodium lauroyl alanine, sodium palmitoyl sarcosinate, and sodium myristoyl sarcosinate, which can synergistically work with ammonia-based organic acids to construct a hydrophobic surface. Excessive concentration of ammonia-based surfactants can easily lead to irregularities in the appearance of the hydrophobic film.

[0011] As a preferred embodiment, the corrosion inhibitor is any one or a mixture of at least two of sodium tripolyphosphate, sodium hexametaphosphate, aminotrimethylenephosphonic acid, and hydroxyethylidene diphosphonic acid. Adding an appropriate amount of corrosion inhibitor can improve the corrosion resistance of the film, while excessive concentration will reduce the surface hydrophobic effect.

[0012] As a preferred embodiment, the pH buffer is any one or a mixture of at least two of sodium acetate, ammonium acetate, sodium citrate, benzoic acid, and ammonium benzoate, used to stabilize the pH value of the system and make the film-forming reaction more stable and efficient.

[0013] The present invention also provides a method for preparing the aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions. The specific steps are as follows: magnesium acetate, ammonia organic acid, ammonia surfactant and corrosion inhibitor are added to deionized water and stirred until completely dissolved. Then, the pH of the system is adjusted to 5-6 with a pH buffer to obtain the aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions.

[0014] The sealing agent of this invention can be used to seal pores in anodized films of aluminum or aluminum alloys. The application process is as follows: the anodized aluminum or aluminum alloy workpiece is immersed in the sealing agent for sealing treatment. The sealing agent temperature is 80~95℃, and the sealing time is 40~60 minutes. After sealing, the workpiece is removed and washed with water to remove residual liquid from the surface, and then dried to obtain a completely sealed anodized film layer with good hydrophobicity.

[0015] Compared with the prior art, the beneficial effects of the present invention are reflected in: (1) The sealing agent of the present invention is based on magnesium acetate as the main salt, compounded with ammonia organic acids, ammonia surfactants and corrosion inhibitors, and the system is non-toxic and environmentally friendly. Among them, magnesium salt has low toxicity, high temperature resistance, certain conductivity, excellent corrosion resistance and strong adhesion; ammonia organic acids and ammonia surfactants work synergistically to form a hydrophobic structure on the oxide film surface; the corrosion inhibitor, as a film-forming promoter, can passivate the film layer, making the film layer more dense and reducing porosity, further improving corrosion resistance, fundamentally solving the problems of high toxicity and poor corrosion resistance of traditional chemical conversion films.

[0016] (2) The aluminum alloy surface treatment method provided by the present invention involves immersing the anodized aluminum alloy in the sealing agent for sealing treatment, thereby forming a closed, dense, and hydrophobic protective film on its surface in situ, which can significantly improve the corrosion resistance and service life of the aluminum alloy. This process is simple, mild, has a short film formation time, is environmentally friendly, and has low cost, making it suitable for industrial production. It has high application value in the field of aluminum and aluminum alloy anodized film treatment. Attached Figure Description

[0017] Figure 1 The surface microstructure of aluminum alloy after sealing with the sealing agent of Example 2; Figure 2 The microstructure of the internal pores of the aluminum alloy after sealing with the sealing agent of Example 2; Figure 3 The surface water droplet angle of aluminum alloy after sealing with different sealing agents according to different embodiments and comparative examples. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Unless otherwise specified, all raw materials used in this invention are commercially available conventional reagents that can be purchased through conventional commercial channels.

[0020] Example 1 This embodiment provides an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions, which is composed of the following components in mass concentration: magnesium acetate 2g / L, glutamic acid 4g / L, sodium lauroyl sarcosinate 0.5g / L, sodium hexametaphosphate 0.02g / L, sodium acetate 2g / L, and the balance being deionized water.

[0021] The specific preparation steps of the sealing agent in this embodiment are as follows: Take 4 / 5 of the total amount of deionized water, heat it to 90°C, and add other raw materials except pH buffer while stirring, and continue stirring until each component is completely dissolved; add the remaining deionized water and stir evenly, then add pH buffer to adjust the pH of the system to 5.5, and continue stirring for 5 minutes to obtain the sealing agent.

[0022] Example 2 This embodiment provides a sealing agent for aluminum alloy anodized film that combines sealing and hydrophobic functions, composed of the following components at the following mass concentrations: magnesium acetate 4 g / L, glutamic acid 2 g / L, aspartic acid 1 g / L, sodium lauroyl alanine 0.2 g / L, aminotrimethylene phosphonic acid 0.05 g / L, ammonium acetate 1 g / L, with the balance being deionized water.

[0023] The specific preparation steps of the sealing agent in this embodiment are the same as those in Example 1.

[0024] Example 3 This embodiment provides an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions, which is composed of the following components in mass concentration: magnesium acetate 5g / L, histidine 2g / L, aspartic acid 2g / L, palmitoyl sarcosinate sodium 0.3g / L, hydroxyethylidene diphosphonic acid 0.03g / L, sodium citrate 1.5g / L, and the balance being deionized water.

[0025] The specific preparation steps of the sealing agent in this embodiment are the same as those in Example 1.

[0026] Example 4 This embodiment provides an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions, which is composed of the following components in mass concentration: magnesium acetate 6g / L, histidine 3g / L, phenylalanine 1g / L, sodium palmitoyl sarcosinate 0.4g / L, sodium tripolyphosphate 0.08g / L, benzoic acid 1.5g / L, and the balance being deionized water.

[0027] The specific preparation steps of the sealing agent in this embodiment are the same as those in Example 1.

[0028] Example 5 This embodiment provides a sealing agent for aluminum alloy anodized film that combines sealing and hydrophobic functions, composed of the following components at the following mass concentrations: magnesium acetate 7g / L, aspartic acid 4g / L, phenylalanine 2g / L, sodium myristoyl sarcosinate 0.4g / L, hydroxyethylidene diphosphonic acid 0.1g / L, sodium benzoate 0.5g / L, with the balance being deionized water.

[0029] The specific preparation steps of the sealing agent in this embodiment are the same as those in Example 1.

[0030] Comparative Example 1 This comparative example provides a sealing agent composed of the following components at mass concentrations: magnesium acetate 4 g / L, glutamic acid 2 g / L, aspartic acid 1 g / L, sodium dodecylbenzenesulfonate 0.2 g / L, aminotrimethylenephosphonic acid 0.05 g / L, ammonium acetate 1 g / L, with the balance being deionized water.

[0031] The specific preparation steps of the sealing agent in this comparative example are the same as those in Example 1.

[0032] The difference between this comparative example and Example 2 is that the ammonia surfactant is replaced with the sulfur-containing surfactant sodium dodecylbenzenesulfonate.

[0033] Comparative Example 2 This comparative example provides a sealing agent composed of the following components at mass concentrations: magnesium acetate 4 g / L, glutamic acid 2 g / L, aspartic acid 1 g / L, sodium lauroyl alanine 0.2 g / L, ammonium acetate 1 g / L, with the balance being deionized water.

[0034] The specific preparation steps of the sealing agent in this comparative example are the same as those in Example 1.

[0035] The difference between this comparative example and Example 2 is that no corrosion inhibitor component was added.

[0036] Comparative Example 3 This comparative example provides a sealing agent composed of the following components at mass concentrations: 4 g / L magnesium acetate, 0.2 g / L sodium lauroyl alanine, 0.05 g / L aminotrimethylene phosphonic acid, 1 g / L ammonium acetate, with the balance being deionized water.

[0037] The specific preparation steps of the sealing agent in this comparative example are the same as those in Example 1.

[0038] The difference between this comparative example and Example 2 is that no ammonia-based organic acid components were added.

[0039] To verify the actual application effect of the sealing agent of the present invention, the sealing agents prepared in Examples 1-5 and Comparative Examples 1-3 were uniformly prepared using the following sealing treatment steps: the aluminum alloy workpieces that had undergone anodizing and water washing were completely immersed in the corresponding sealing agent for constant temperature sealing treatment; the pH of the sealing agent was controlled at 5.5, the sealing temperature was controlled at 90°C, and the sealing time was controlled at 50 min. After sealing, the workpieces were removed, the surface residual liquid was rinsed with deionized water, and the workpieces were air-dried at room temperature for later performance testing.

[0040] 1. Corrosion weight loss test The sealing quality of anodic oxide films was tested according to GB / T 8753.1-2017 "Evaluation Method for Sealing Quality of Anodized Oxide Films of Aluminum and Aluminum Alloys Part 1: Acid Etching Weight Loss Method". The specific steps are as follows: (1) Measure the effective surface area of ​​the sample. Wipe off any frost on the sample surface with a dry cloth. At room temperature, stir the sample in a suitable organic solvent for 30 seconds or wash it to remove grease.

[0041] (2) Air-dry the sample at room temperature for 5 minutes, then place it upright in a drying oven preheated to 60°C and dry for 15 minutes. Then, place the sample in a sealed desiccator above silica gel and cool for 30 minutes. Finally, remove the sample and weigh it.

[0042] (3) Immerse the sample upright in the pre-soaking solution at a temperature of 19℃±1℃ for 10 minutes. Then remove the sample from the pre-soaking solution and wash it thoroughly with tap water and then with distilled water.

[0043] (4) Immerse the sample upright in a phosphoric acid solution preheated to 38℃±1℃ for 13 minutes. Then remove the sample from the phosphoric acid solution and wash it thoroughly with tap water and then with distilled water.

[0044] (5) Dry the sample according to step (2) and weigh the sample after drying. Calculate the mass loss per unit area of ​​the sample after corrosion.

[0045] 2. Water droplet angle test A water droplet angle tester was used to test the hydrophobicity of the sealed sample surface and record the water droplet angle values. Figure 3 A higher value indicates better hydrophobicity.

[0046] Table 1

[0047] Test data shows that in comparative samples that did not use the sealing agent components of this invention, lacked the core additives, or had their surfactants replaced, the surface morphology of the samples deteriorated, hydrophobicity decreased significantly, and phosphoric acid corrosion weight loss increased significantly. The sealing quality and corrosion resistance were far from satisfactory. Using the sealing agent of this invention, a hydrophobic surface can be constructed simultaneously with sealing, achieving a balance between sealing quality, hydrophobicity, and corrosion resistance, thus significantly improving the overall protective performance of aluminum alloy anodic oxide films.

[0048] Figure 1 The surface microstructure of aluminum alloy after sealing with the sealing agent of Example 2 shows that the film layer is flat and dense, without obvious pores or cracks, and only a small number of uniform and fine nano-sized particles are distributed, indicating that the sealing agent effectively fills the micropores of the anodic oxide film and forms a continuous and complete hydrophobic protective layer. Figure 2 The microstructure of the internal pores of the aluminum alloy after sealing with the sealing agent of Example 2 shows that the pores inside the film are fully sealed and the pore structure is densified, which can effectively block the penetration of corrosive media. Figure 3 The surface water droplet angles of aluminum alloys after sealing with different sealing agents in different embodiments and comparative examples show the differences in the hydrophobic properties of the formed film.

[0049] This invention is not limited to the specific embodiments described above. Any equivalent substitution of raw material components or conventional adjustment of process parameters within the scope of the technical concept of this invention shall fall within the protection scope of this invention.

Claims

1. A sealing agent for aluminum alloy anodized films that combines sealing and hydrophobic functions, characterized in that, It consists of components with the following mass concentrations: Magnesium acetate 1~7g / L; Ammonia-based organic acids: 0.5~5 g / L; Ammonia-based surfactants: 0.1~1 g / L; Corrosion inhibitor 0.01~0.2g / L; pH buffer 0.5~2g / L; The remaining amount is deionized water; The ammonia-based organic acid is any one or a mixture of at least two of glutamic acid, aspartic acid, histidine, and phenylalanine; the ammonia-based surfactant is any one or a mixture of at least two of sodium lauroyl sarcosinate, sodium lauroyl alanine, sodium palmitoyl sarcosinate, and sodium myristoyl sarcosinate; and the corrosion inhibitor is any one or a mixture of at least two of sodium tripolyphosphate, sodium hexametaphosphate, aminotrimethylene phosphonic acid, and hydroxyethylidene diphosphonic acid.

2. The sealing agent for aluminum alloy anodized films with both sealing and hydrophobic functions according to claim 1, characterized in that, The pH buffer is any one or a mixture of at least two of sodium acetate, ammonium acetate, sodium citrate, benzoic acid, and sodium benzoate.

3. A method for preparing a sealing agent for aluminum alloy anodic oxide films with both sealing and hydrophobic functions as described in any one of claims 1 to 2, characterized in that, The specific steps are as follows: Add magnesium acetate, ammonia organic acids, ammonia surfactants, and corrosion inhibitors to deionized water and stir until completely dissolved. Then, adjust the pH of the system to 5-6 with a pH buffer to obtain an aluminum alloy anodic oxide film sealing agent with both sealing and hydrophobic functions.

4. The application of a sealing agent for aluminum alloy anodized films with both sealing and hydrophobic functions as described in any one of claims 1 to 2, characterized in that, The sealing agent is used to seal the pores of anodized aluminum or aluminum alloy films.

5. The application according to claim 4, characterized in that, The specific method of the application is as follows: the anodized aluminum or aluminum alloy workpiece is immersed in the sealing agent for sealing treatment, the temperature of the sealing agent is 80~95℃, and the sealing time is 40~60min.

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