Conductive oxidation solution for aluminum alloy material and conductive oxidation method for aluminum alloy material

Abstract

The invention provides a conductive oxidation solution for an aluminum alloy material and a conductive oxidation method for the aluminum alloy material, and belongs to the technical field of alloy material surface protection. The conductive oxidation liquid for the aluminum alloy material comprises the following components: 2.5 g / L to 3 g / L of chromic anhydride, 2.0 g / L to 2.5 g / L of potassium dichromate and 1 g / L to 1.2 g / L of sodium fluoride. The conductive oxidation liquid for the aluminum alloy material is adopted for chemical oxidation, and a conductive oxidation layer formed on the surface of the aluminum alloy not only has good conductivity, but also has good corrosion resistance and high-temperature stability.

Description

Technical Field

[0001] The invention belongs to the technical field of surface protection of alloy materials, and in particular relates to a conductive oxidizing solution for aluminum alloy materials and a method for conductive oxidation of aluminum alloy materials. Background Art

[0002] Aluminum alloy is a commonly used metal material with excellent conductivity and plasticity. It is widely used in aerospace and other fields. However, the oxide film generated by aluminum alloy in the air is very thin and not corrosion-resistant. At the same time, due to the low surface hardness of aluminum alloy materials, wear resistance is also poor. Therefore, anodizing technology was subsequently developed as a surface protection for aluminum alloys. However, the surface of the anodized film layer is not conductive and has electromagnetic shielding phenomenon. It is not suitable for application to certain key parts, which limits the application field. Therefore, it is particularly important to provide a method that can improve the corrosion resistance and high temperature stability of aluminum alloys without affecting conductivity. Summary of the invention

[0003] The present invention provides a conductive oxidizing solution for an aluminum alloy material and a method for conductive oxidation of the aluminum alloy material. The conductive oxidizing solution for the aluminum alloy material provided by the present invention is used for chemical oxidation, and a conductive oxide layer formed on the surface of the aluminum alloy has not only good conductivity but also good corrosion resistance and high-temperature stability.

[0004] In order to achieve the above object, the present invention provides a conductive oxidation solution for aluminum alloy material, comprising the following components:

[0005] Chromic anhydride 2.5-3g / L, potassium dichromate 2.0-2.5g / L and sodium fluoride 1-1.2g / L.

[0006] The present invention also provides a method for conductive oxidation of aluminum alloy materials, comprising the following steps:

[0007] 1) pretreating the aluminum alloy material to obtain a pretreated aluminum alloy;

[0008] 2) The pretreated aluminum alloy is chemically oxidized using the conductive oxidizing solution described in the above scheme to obtain an aluminum alloy having a conductive oxide layer.

[0009] Preferably, the pretreatment in step 1) includes surface cleaning, degreasing, pickling and water washing.

[0010] Preferably, the surface is cleaned by first grinding or brushing and then washing with water.

[0011] Preferably, the degreasing method is as follows: firstly, cleaning with an aluminum cleaning agent, then washing with water, and then drying the aluminum alloy after washing; chemically degreasing the aluminum alloy after drying, and then washing with running hot water and running cold water.

[0012] Preferably, when the aluminum cleaning agent is used for cleaning, the cleaning time is 2 to 5 minutes and the pH value is 10 to 12.

[0013] Preferably, each liter of chemical degreasing agent includes the following components: 15-25 g of sodium hydroxide, 10-30 g of trisodium phosphate, and 5-10 g of sodium silicate; the temperature during the chemical degreasing is controlled at 70-80°C.

[0014] Preferably, during pickling, 300 to 500 g of nitric acid is included per liter of pickling solution.

[0015] Preferably, the temperature during the chemical oxidation in step 2) is 40-60° C., and the temperature is kept constant for 5-8 minutes.

[0016] Preferably, after the chemical oxidation is completed, the process further comprises washing with running cold water, washing with pure water, and drying at 50-60°C.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are:

[0018] The present invention provides a conductive oxidation solution for aluminum alloy materials. Chromic anhydride reacts with water in the conductive oxidation solution to form chromic acid. Chromic acid and potassium dichromate react with aluminum on the surface of an aluminum substrate under acidic conditions. Under a certain temperature, the reaction activator sodium fluoride catalyzes the reaction to form a chromate film layer. The film layer is activated under the control of appropriate process parameters such as temperature and time, and contains highly reactive hydroxyl groups. After being sealed with pure water and dried, a complete, dense, golden oxide film layer is formed on the surface. It not only has good electrical conductivity, but also has good corrosion resistance and high-temperature stability. At the same time, the solution has a simple formula, convenient component detection and maintenance, and can meet temperature requirements by heating with an electric heating rod.

[0019] The present invention also provides a method for conductive oxidation of aluminum alloy materials, wherein the aluminum alloy material is pretreated and then chemically oxidized to form a golden conductive oxide layer on the surface of the aluminum alloy, which not only has good conductive properties, but also can be widely used in electronic components. At the same time, it has good corrosion resistance and high temperature stability, and can still maintain excellent performance under extreme working conditions. At the same time, the conductive oxidized golden aluminum alloy has a unique golden appearance, making it popular in the fields of home appliances and automobiles. Its golden appearance is not only beautiful and generous, but also has high-end and fashionable qualities, making the product more attractive. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a physical picture of the aluminum alloy part after chemical oxidation to form a conductive oxide layer in Example 1;

[0021] Figure 2 This is a physical picture of the aluminum alloy part after chemical oxidation to form an oxide layer in Comparative Example 1;

[0022] Figure 3 This is a physical picture of the aluminum alloy part after chemical oxidation to form an oxide layer in Comparative Example 2. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The present invention provides a conductive oxidation solution for aluminum alloy material, comprising the following components:

[0025] Chromic anhydride 2.5-3g / L, potassium dichromate 2.0-2.5g / L and sodium fluoride 1-1.2g / L.

[0026] In the present invention, the aluminum alloy material uses chromic anhydride in a conductive oxidation solution to react with water to form chromic acid, and chromic acid and potassium dichromate react with aluminum on the surface of the aluminum substrate under acidic conditions, and are promoted at a certain temperature and catalyzed by a reaction activator, sodium fluoride, to form a chromate film layer. The film layer is activated under the control of appropriate process parameters such as temperature and time, and contains highly reactive hydroxyl groups. After being sealed with pure water and dried, a complete, dense, golden oxide film layer is formed on the surface.

[0027] The present invention provides a method for conductive oxidation of an aluminum alloy material, comprising the following steps:

[0028] 1) pretreating the aluminum alloy material to obtain a pretreated aluminum alloy;

[0029] 2) The pretreated aluminum alloy is chemically oxidized using the conductive oxidizing solution described in the above scheme to obtain an aluminum alloy having a conductive oxide layer.

[0030] The present invention pre-treats the aluminum alloy material to obtain the pre-treated aluminum alloy. In the present invention, the pre-treatment preferably includes surface cleaning, degreasing, pickling and water washing. In the present invention, the surface cleaning is preferably first polished or brushed, and then washed with water. In the present invention, when washing with water after polishing or brushing, the water temperature is preferably 15 to 30°C. In the present invention, surface cleaning is performed to facilitate cleaning of impurities on the surface and cutting fluids, emulsions, etc. incidental to the machining process.

[0031] In the present invention, the degreasing method is preferably as follows: firstly, the aluminum material cleaning agent is used for cleaning, and then the aluminum material is washed with water after cleaning, and then the aluminum material is dried after washing; the aluminum alloy after drying is chemically degreased, and then washed with running hot water and running cold water. In the present invention, the pH value of the aluminum material cleaning agent is preferably 10 to 12, the washing time is preferably 2 to 5 minutes, and the temperature is preferably 15 to 30°C. In the present invention, when the aluminum material cleaning agent is used for washing after cleaning, the water temperature is preferably 15 to 30°C.

[0032] The present invention has no special limitation on the source of the aluminum cleaning agent, and a conventional commercial product in the field can be used. In the embodiment of the present invention, Tianjin Komiou SK-224 is used. When in use, the cleaning agent is mixed with water in a ratio of 5 to 8:100 before use.

[0033] In the present invention, when chemical degreasing is performed, the temperature is preferably controlled at 70-80°C. In the present invention, each liter of chemical degreasing agent preferably includes the following components: 15-25g of sodium hydroxide, 10-30g of trisodium phosphate, and 5-10g of sodium silicate. In the present invention, the water temperature during the running hot water cleaning is 90-95°C. In the present invention, the water temperature during the running cold water cleaning is preferably 15-30°C. In the present invention, when pickling is performed, each liter of pickling solution preferably includes 300-500g of nitric acid.

[0034] The present invention pre-treats the aluminum alloy material, and sequentially performs surface cleaning, degreasing, pickling and water washing to remove surface cutting fluid or oil stains, activate the surface matrix metal, and thus facilitate the formation of an oxide film.

[0035] After obtaining the pretreated aluminum alloy, the present invention uses the conductive oxidation solution described in the above scheme to chemically oxidize the pretreated aluminum alloy to obtain an aluminum alloy with a conductive oxide layer. In the present invention, the temperature during the electrolytic oxidation is preferably 40 to 60°C, and the temperature is kept constant for 5 to 8 minutes. In the present invention, the chemical oxidation is carried out under the above conditions, and the thickness of the oxide film formed on the aluminum alloy after oxidation can be controlled between 0.5 and 8 μm, and the conductive resistance value is less than 1.5 ohms.

[0036] In the present invention, after the electrolytic oxidation is completed, it is preferred that the process further comprises washing with running cold water, washing with pure water, and drying at 50-60°C.

[0037] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0038] Example 1

[0039] After polishing the surface of the aluminum alloy parts, use deionized water to clean them, and check that the parts have no mechanical deformation and mechanical damage, cracks, spots, pits, etc. The cleaned parts are first cleaned with aluminum cleaning agent (measured pH value is 10) for 3 minutes; after cleaning, use deionized water to wash, dry after washing, and then immerse the parts in 75°C chemical degreasing agent (each liter of chemical degreasing agent consists of the following components: 20g sodium hydroxide, 20g trisodium phosphate, 8g sodium silicate and the rest of water) for chemical degreasing. After degreasing, use 92°C flowing hot water to wash for 2 minutes, and then use 20°C flowing cold water to wash for 2 minutes. After cleaning, immerse in pickling solution (each liter of pickling solution consists of 400g nitric acid and rest water, pH value is 2) and soak for 2 minutes. Finally, use 20°C flowing deionized water to wash for 2 minutes. The pretreated aluminum alloy is obtained.

[0040] The pretreated aluminum alloy was immersed in a conductive oxidation solution (the components and concentrations of the conductive oxidation solution are as follows: 2.7 g / L chromic anhydride, 2.2 g / L potassium dichromate and 1.1 g / L sodium fluoride), oxidized at 50°C for 6 minutes, and a continuous and complete golden conductive oxide layer was formed on the surface of the aluminum alloy. The parts were taken out of the solution, washed with 20°C running cold water, washed with pure water, and finally dried at 55°C. The prepared parts are as follows Figure 1 shown.

[0041] Example 2

[0042] After polishing the surface of the aluminum alloy parts, use deionized water to clean them, and check that the parts have no mechanical deformation and mechanical damage, cracks, spots, pits, etc. The cleaned parts are first cleaned with aluminum cleaning agent (measured pH value is 10) for 2 minutes; after cleaning, use deionized water to wash, dry, and then immerse the parts in 70°C chemical degreasing agent (each liter of chemical degreasing agent consists of the following components: 15g sodium hydroxide, 10g trisodium phosphate, 5g sodium silicate and the rest of water) for chemical degreasing. After degreasing, use 92°C flowing hot water to wash for 2 minutes, and then use 25°C flowing cold water to wash for 2 minutes. After cleaning, immerse in pickling solution (each liter of pickling solution consists of 300g nitric acid and rest water, pH value is 2) and soak for 1 minute. Finally, use 25°C flowing deionized water to wash for 2 minutes. The pretreated aluminum alloy is obtained.

[0043] The pretreated aluminum alloy was immersed in a conductive oxidation solution (the components and concentrations of the conductive oxidation solution are as follows: 2.5g / L chromic anhydride, 2.0g / L potassium dichromate and 1g / L sodium fluoride), and electrolyzed at 40°C for 5 minutes to form a continuous and complete golden conductive oxide layer on the surface of the aluminum alloy. The parts were taken out of the solution, washed with 25°C running cold water, washed with pure water, and finally dried at 50°C.

[0044] Example 3

[0045] After polishing the surface of the aluminum alloy parts, use deionized water to clean them, and check that the parts have no mechanical deformation and mechanical damage, cracks, spots, pits, etc. The cleaned parts are first cleaned with aluminum cleaning agent (the measured pH value is 10) for 2 minutes, and then washed with deionized water after cleaning, dried, and then immersed in 80°C chemical degreasing agent (each liter of chemical degreasing agent consists of the following components: 25g sodium hydroxide, 30g trisodium phosphate, 10g sodium silicate and the rest of water) for chemical degreasing. After degreasing, use 92°C flowing hot water to clean for 2 minutes, and then use 25°C flowing cold water to clean for 2 minutes. After cleaning, immerse in pickling solution (each liter of pickling solution consists of 500g nitric acid and rest water, and the pH value is 2) for 3 minutes. Finally, use 25°C flowing deionized water to clean for 2 minutes. The pretreated aluminum alloy is obtained.

[0046] The pretreated aluminum alloy was immersed in a conductive oxidation solution (the components and concentrations of the conductive oxidation solution are as follows: 3.0 g / L chromic anhydride, 2.5 g / L potassium dichromate and 1.2 g / L sodium fluoride), oxidized at 60°C for 8 minutes, and a continuous and complete golden conductive oxide layer was formed on the surface of the aluminum alloy. The parts were taken out of the solution, washed with 25°C running cold water, washed with pure water, and finally dried at 60°C.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that the conductive oxidation solution is different. The other operations are exactly the same as Example 1. The specific composition of the conductive oxidation solution is as follows: 12 g / L phosphoric acid, 2.2 g / L potassium dichromate, 1.1 g / L sodium fluoride, such as Figure 2 As shown, the surface of aluminum alloy parts turns khaki after conductive oxidation.

[0049] Comparative Example 2

[0050] The difference from Example 1 is that the conditions for chemical oxidation of the conductive oxidizing solution are different, and the other operations are exactly the same as Example 1. The specific conditions are: temperature 30°C, time 3 minutes. Figure 3 As shown, the surface of aluminum alloy parts presents rainbow galvanized color after conductive oxidation.

[0051] Performance Testing

[0052] The performance of the alloys finally obtained in Examples 1 to 3 and Comparative Examples 1 to 2 was tested, and the specific test results are shown in Table 1.

[0053] Among them: The corrosion resistance test uses a 10% sodium chloride aqueous solution to simulate seawater corrosion test, immerse the parts in the 10% sodium chloride aqueous solution for 15 days, observe the surface color and whether there are corrosion spots. Bake at 60℃ for 24h to test high temperature stability.

[0054] Table 1

[0055]

[0056]

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A conductive oxidizing solution for aluminum alloy material, characterized in that: The components include: Chromic anhydride 2.5-3g / L, potassium dichromate 2.0-2.5g / L and sodium fluoride 1-1.2g / L.

2. A method for conductive oxidation of aluminum alloy material, characterized in that: The steps include: 1) pretreating the aluminum alloy material to obtain a pretreated aluminum alloy; 2) The pretreated aluminum alloy is chemically oxidized using the conductive oxidizing solution of claim 1 to obtain an aluminum alloy having a conductive oxide layer.

3. The method according to claim 2, characterized in that The pretreatment in step 1) includes surface cleaning, degreasing, pickling and water washing.

4. The method according to claim 3, characterized in that The surface cleaning is first polishing or brushing, and then washing with water.

5. The method according to claim 3, characterized in that: The degreasing method is as follows: firstly, cleaning with an aluminum cleaning agent, then washing with water, and then drying the aluminum alloy after washing; chemically degreasing the aluminum alloy after drying, and then washing with running hot water and running cold water.

6. The method according to claim 5, characterized in that When using aluminum cleaning agent for cleaning, the cleaning time is 2 to 5 minutes and the pH value is 10 to 12.

7. The method according to claim 5, characterized in that Each liter of chemical degreasing agent includes the following components: 15-25g of sodium hydroxide, 10-30g of trisodium phosphate, and 5-10g of sodium silicate; the temperature during the chemical degreasing is controlled at 70-80°C.

8. The method according to claim 3, characterized in that When pickling, 300 to 500 g of nitric acid is included per liter of pickling solution.

9. The method according to claim 2, characterized in that: The temperature of the chemical oxidation in step 2) is 40-60° C., and the temperature is kept constant for 5-8 minutes.

10. The method according to claim 2, characterized in that After the chemical oxidation is completed, it also includes washing with running cold water, washing with pure water, and drying at 50-60°C.

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