Pretreatment polishing solution before anodic oxidation of aluminum alloy as well as preparation method and application of pretreatment polishing solution

Abstract

The invention provides a pretreatment polishing solution before anodic oxidation of an aluminum alloy, which is prepared from the following raw materials in percentage by weight: 69%-72% of sulfuric acid, 10%-15% of phosphoric acid, 5%-8% of pyrophosphoric acid, 5%-8% of phosphorus pentoxide, 1.8%-2.25% of composite metal sulfate, 0.1%-0.15% of tartaric acid, 0.1%-0.15% of benzotriazole and 0.5%-1% of imidazole. The invention further provides a preparation method of the polishing solution and application of the polishing solution in pretreatment before aluminum alloy anodic oxidation. The polishing solution provided by the invention can remarkably improve the macroscopic surface and the surface microstructure of the polished aluminum alloy, provides a good structural basis for forming a uniform and compact oxidation film on the aluminum surface in the subsequent aluminum alloy anodic oxidation process, and has important significance for improving the quality and the market competitiveness of an aluminum alloy final product; wide popularization and application prospects are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material surface treatment, and specifically relates to a pretreatment polishing liquid before anodizing of an aluminum alloy, and a preparation method and application thereof. Background Art

[0002] Aluminum alloy anodizing structural color technology is a surface treatment technology that forms an oxide film on the surface of aluminum alloy through an electrochemical process and achieves different colors by controlling the parameters in the oxidation process. This technology can not only significantly improve the appearance quality of aluminum alloy, but also enhance its corrosion resistance and wear resistance, so it has broad application prospects in the fields of aviation, automobiles, construction and decoration.

[0003] The pretreatment of aluminum alloy anodizing is a key step to ensure the quality of anodizing. The main purpose of pretreatment is to improve the microstructure of the surface and polish the macroscopic surface so that a uniform and dense oxide film can be formed on the aluminum surface during the anodizing process. The quality of pretreatment directly affects the adhesion, thickness, uniformity of the anodized film and the final surface treatment effect, including the generation of structural color. If the pretreatment is improper, defects in the anodized film may occur, such as uneven porosity, incomplete film layer, uneven color, etc. These defects not only affect the appearance quality of the product, but also may reduce its corrosion resistance and wear resistance, thereby affecting the overall performance and service life of the product.

[0004] It can be seen that the pre-treatment of aluminum alloy anodizing is crucial to ensure the success of subsequent surface treatment processes such as structural color. Based on this, providing a polishing liquid that can improve the macroscopic surface and microstructure of polished aluminum alloy, and providing a good structural foundation for the formation of a uniform and dense oxide film on the aluminum surface during the subsequent aluminum alloy anodizing process, is of great significance for improving the quality and market competitiveness of aluminum alloy final products, and is also a technical problem that needs to be solved urgently. Summary of the invention

[0005] One of the purposes of the present invention is to provide a pretreatment polishing liquid before anodizing of aluminum alloy.

[0006] A second object of the present invention is to provide a method for preparing a pretreatment polishing liquid before anodizing of aluminum alloy.

[0007] A third object of the present invention is to provide an application of a pretreatment polishing liquid before anodizing of aluminum alloy.

[0008] The technical solution adopted by the present invention to achieve one of the purposes is: a pretreatment polishing liquid before anodizing of aluminum alloy, the polishing liquid is composed of the following raw materials in terms of weight percentage: Sulfuric acid 69%-72%, phosphoric acid 10%-15%, pyrophosphoric acid 5%-8%, phosphorus pentoxide 5%-8%, complex metal sulfate 1.8%-2.25%, tartaric acid 0.1%-0.15%, benzotriazole 0.1%-0.15%, imidazole 0.5%-1%.

[0009] The polishing liquid provided by the present invention has sulfuric acid and phosphoric acid as main components, and sulfuric acid has a relatively high proportion (mass percentage is 69%-72%). In addition, a certain proportion of pyrophosphoric acid and phosphorus pentoxide are added to the polishing liquid of the present invention, which can reduce the moisture in the formula and improve the polishing effect on the one hand; on the other hand, the addition of pyrophosphoric acid and phosphorus pentoxide can not only increase the phosphoric acid content, but also help to extend the service life of the polishing liquid. Furthermore, a certain proportion of benzotriazole is added to the formula as a precipitation film-type corrosion inhibitor, and a certain proportion of imidazole is added to prevent the generation of static electricity, thereby improving the polishing pretreatment effect and facilitating the smooth progress of the subsequent anodizing process.

[0010] Furthermore, the mass percentage concentration of the sulfuric acid is not less than 98%.

[0011] Furthermore, the mass percentage concentration of the phosphoric acid is not less than 85%.

[0012] Furthermore, the composite metal sulfate includes aluminum sulfate 18hydrate, anhydrous ferric sulfate and zinc sulfate heptahydrate. The composite metal sulfate composed of aluminum sulfate 18hydrate, anhydrous ferric sulfate and zinc sulfate heptahydrate used in the present invention can be well dissolved in the mixed acid system, simplifying the preparation process, and avoiding the defect of inconsistent color on the surface of the aluminum alloy caused by the use of chloride salts.

[0013] Preferably, the polishing liquid is composed of the following raw materials in weight percentage: 69%-72% sulfuric acid, 10%-15% phosphoric acid, 5%-8% pyrophosphoric acid, 5%-8% phosphorus pentoxide, 1.5%-1.7% aluminum sulfate 18hydrate, 0.2%-0.4% anhydrous ferric sulfate, 0.1%-0.15% zinc sulfate heptahydrate, 0.1%-0.15% tartaric acid, 0.1%-0.15% benzotriazole, and 0.5%-1% imidazole.

[0014] The technical solution adopted by the present invention to achieve the second purpose is: to provide a method for preparing a pretreatment polishing liquid before anodizing of an aluminum alloy according to one of the purposes of the present invention, comprising the following steps: S1, mixing concentrated sulfuric acid, phosphoric acid and pyrophosphoric acid to obtain a mixed acid; S2, adding phosphorus pentoxide to the mixed acid, stirring until fully dissolved, to obtain a mixed solution; S3. Add aluminum sulfate 18hydrate, anhydrous ferric sulfate, zinc sulfate heptahydrate, tartaric acid, benzotriazole and imidazole to the mixed solution, and mix thoroughly to obtain a polishing solution.

[0015] In the above preparation method, sulfuric acid, phosphoric acid and pyrophosphoric acid are first added according to the composition of the polishing liquid to form a mixed acid. The pyrophosphoric acid can react with the water in the phosphoric acid in a relatively short time to reduce the water content in the mixed acid. After the water content is reduced, phosphorus pentoxide is added to continue the reaction and then phosphorus pentoxide is added. Stirring at room temperature until completely dissolved, finally adding the remaining components and stirring until completely dissolved, the preparation of the polishing liquid is completed.

[0016] The technical solution adopted by the present invention to achieve the third purpose is: to provide an application of the pretreatment polishing liquid before anodizing of aluminum alloys according to one of the purposes of the present invention or the pretreatment polishing liquid before anodizing of aluminum alloys prepared by the preparation method according to the second purpose of the present invention, and the application includes: placing the aluminum alloy material in the polishing liquid at a certain temperature and soaking it for a certain period of time, then taking it out, washing it with water and drying it, so as to obtain the polished aluminum alloy material.

[0017] Furthermore, the temperature of the polishing liquid is 120-130°C.

[0018] Furthermore, the soaking time is 45-60 seconds.

[0019] In the present invention, for the polishing agent system of the present invention, a suitable polishing temperature and time are set to ensure the polishing effect. When the temperature or time is higher than the above range, the aluminum alloy surface will be excessively oxidized and the surface flatness will be destroyed; when the temperature or time is lower than the above range, the polishing effect is not obvious, and the improvement on the aluminum alloy surface is not obvious.

[0020] Furthermore, the aluminum alloy material is an aluminum alloy plate.

[0021] Preferably, the application comprises the following steps: (1) Add the prepared pretreatment polishing liquid for aluminum alloy anodizing into a water tank equipped with a water cooling system and heat it to 120-130°C; (2) Immerse the clean aluminum alloy material in the polishing liquid, turn on the condensation water, soak it at 120-130℃ for 45-60 seconds and then take it out; (3) The aluminum alloy material is quickly washed in cold water and dried to obtain a polished aluminum alloy material.

[0022] Preferably, the aluminum alloy material is an aluminum alloy plate.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The pretreatment polishing liquid before anodizing of aluminum alloy provided by the present invention adds a certain proportion of pyrophosphoric acid and phosphorus pentoxide, which can reduce the water content in the formula and improve the polishing effect on the one hand; on the other hand, increasing the addition of the two can increase the phosphoric acid content in the system, which is beneficial to prolonging the service life of the polishing liquid. The pretreatment polishing liquid before anodizing of aluminum alloy provided by the present invention has easy-to-obtain raw materials, a simple preparation method, and convenient operation.

[0024] (2) The pretreatment polishing liquid before anodizing of aluminum alloy provided by the present invention is applied to the pretreatment operation before anodizing of aluminum alloy, which can significantly improve the macroscopic surface and surface microstructure of the polished aluminum alloy, and provide a good structural basis for forming a uniform and dense oxide film on the aluminum surface during the subsequent anodizing process of the aluminum alloy. It is of great significance for improving the quality and market competitiveness of the final aluminum alloy product, and has broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of a method for preparing a pretreatment polishing liquid before anodizing of an aluminum alloy provided by the present invention; Figure 2 The figures are actual comparison diagrams of the aluminum alloy plate before and after polishing in Example 1 of the present invention; wherein (a) is the unpolished sample; and (b) is the polished sample. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0028] like Figure 1 As shown, the present invention provides a method for preparing a pretreatment polishing liquid before anodizing of aluminum alloy. The present invention is further described below in conjunction with specific embodiments, but is not intended to be a limitation of the present invention.

[0029] In each embodiment of the present invention, the raw materials of the polishing liquid and the amount (g) thereof are shown in Table 1 below.

[0030] Table 1

[0031] In the above table, the mass percentage concentration of sulfuric acid is 98%, and the mass percentage concentration of phosphoric acid is 85%.

[0032] Example 1 Weigh 690g of concentrated sulfuric acid, 150g of phosphoric acid, and 80g of pyrophosphoric acid, mix them, add 50g of phosphorus pentoxide, stir to fully dissolve, then add 15g of aluminum sulfate 18hydrate, 2g of anhydrous ferric sulfate, 1g of zinc sulfate heptahydrate, 1g of tartaric acid, 1g of benzotriazole, and 10g of imidazole, stir to dissolve.

[0033] Transfer the prepared polishing liquid into a reaction tank with a water cooling system and heat it to 120-130℃. Put in an aluminum alloy plate with a length of 12cm and a width of 5cm, soak for 45 seconds, take it out, wash it in clean water, and dry it naturally to get a mirror-like aluminum alloy material. The comparison of the aluminum alloy material before and after polishing is shown below. Figure 2 shown.

[0034] Example 2 Weigh 720g of concentrated sulfuric acid, 100g of phosphoric acid, and 67g of pyrophosphoric acid, mix the two, add 80g of phosphorus pentoxide, stir to fully dissolve, then add 17g of aluminum sulfate 18hydrate, 4g of anhydrous ferric sulfate, 1.5g of zinc sulfate heptahydrate, 1.5g of tartaric acid, 1.5g of benzotriazole, and 7.5g of imidazole, stir to dissolve.

[0035] Transfer the prepared polishing liquid into a reaction tank with a water cooling system and heat it to 130°C. Put in an aluminum alloy plate with a length of 12 cm and a width of 5 cm, soak for 60 seconds, take it out, wash it in clean water, and dry it naturally to obtain a mirror-like aluminum alloy material.

[0036] Example 3 Weigh 710g of concentrated sulfuric acid, 140g of phosphoric acid, and 60g of pyrophosphoric acid, mix the two, add 60g of phosphorus pentoxide, stir to fully dissolve, then add 16g of aluminum sulfate 18hydrate, 2.5g of anhydrous ferric sulfate, 1.2g of zinc sulfate heptahydrate, 1.3g of tartaric acid, 1.2g of benzotriazole, and 7.8g of imidazole, stir to dissolve.

[0037] Transfer the prepared polishing liquid into a reaction tank with a water cooling system and heat it to 130°C. Put in an aluminum alloy plate with a length of 12 cm and a width of 5 cm, soak for 50 seconds, take it out, wash it in clean water, and dry it naturally to obtain a mirror-like aluminum alloy material.

[0038] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of the specification of the present invention should be included in the protection scope of the present invention.

Claims

1. A pretreatment polishing liquid before anodizing of aluminum alloy, characterized in that: The polishing liquid is composed of the following raw materials by weight percentage: Sulfuric acid 69%-72%, phosphoric acid 10%-15%, pyrophosphoric acid 5%-8%, phosphorus pentoxide 5%-8%, complex metal sulfate 1.8%-2.25%, tartaric acid 0.1%-0.15%, benzotriazole 0.1%-0.15%, imidazole 0.5%-1%.

2. The pretreatment polishing liquid before anodizing of aluminum alloy according to claim 1, characterized in that: The mass percentage concentration of the sulfuric acid is not less than 98%.

3. The pretreatment polishing liquid before anodizing of aluminum alloy according to claim 1, characterized in that: The mass percentage concentration of the phosphoric acid is not less than 85%.

4. The pretreatment polishing liquid before anodizing of aluminum alloy according to claim 1, characterized in that: The composite metal sulfate comprises aluminum sulfate 18hydrate, anhydrous ferric sulfate and zinc sulfate heptahydrate.

5. The pretreatment polishing liquid before anodizing of aluminum alloy according to claim 4, characterized in that: The polishing liquid is composed of the following raw materials by weight percentage: Sulfuric acid 69%-72%, phosphoric acid 10%-15%, pyrophosphoric acid 5%-8%, phosphorus pentoxide 5%-8%, aluminum sulfate 18hydrate 1.5%-1.7%, anhydrous ferric sulfate 0.2%-0.4%, zinc sulfate heptahydrate 0.1%-0.15%, tartaric acid 0.1%-0.15%, benzotriazole 0.1%-0.15%, imidazole 0.5%-1%.

6. A method for preparing a pretreatment polishing liquid before anodizing of an aluminum alloy according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, mixing concentrated sulfuric acid, phosphoric acid and pyrophosphoric acid to obtain a mixed acid; S2, adding phosphorus pentoxide to the mixed acid, stirring until fully dissolved, to obtain a mixed solution; S3. Add aluminum sulfate 18hydrate, anhydrous ferric sulfate, zinc sulfate heptahydrate, tartaric acid, benzotriazole and imidazole to the mixed solution, and mix thoroughly to obtain a polishing solution.

7. A use of the pretreatment polishing liquid before anodizing of an aluminum alloy according to any one of claims 1 to 5 or the pretreatment polishing liquid before anodizing of an aluminum alloy obtained by the preparation method according to claim 6, characterized in that: The applications include: The aluminum alloy material is placed in a polishing liquid at a certain temperature and immersed for a certain period of time, then taken out, washed with water and dried to obtain the polished aluminum alloy material.

8. The use according to claim 7, characterized in that: The temperature of the polishing liquid is 120-130°C.

9. The use according to claim 7, characterized in that: The soaking time is 45-60 seconds.

10. The use according to claim 7, characterized in that: The aluminum alloy material is an aluminum alloy plate.

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