Self-healing sealing coating concentrated solution as well as preparation method and application thereof

Abstract

The invention discloses a self-healing closed coating concentrated solution which comprises a first-class complexing agent, a second-class complexing agent, soluble cerium salt, a pH buffering agent, a wetting agent and deionized water. The invention also discloses a preparation method and application of the compound. The sealing coating obtained based on the self-healing sealing coating concentrated solution not only has excellent compactness, but also shows excellent self-healing performance. Meanwhile, preparation and application of the self-healing closed coating concentrated solution are easy to operate, low in cost, environmentally friendly and free of pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and in particular to a self-healing closed coating concentrate, a preparation method and an application thereof. Background Art

[0002] Aluminum alloys are widely used in the aerospace, chemical, shipbuilding, and automotive industries due to their low density, excellent mechanical properties, and good machinability. In practical applications, aluminum alloy surfaces are often treated to enhance their corrosion and wear resistance, using methods such as anodizing, electroless plating, micro-arc oxidation, and hard anodizing. Anodizing, due to its numerous advantages, such as mature technology, low cost, and decorative properties, is widely used to further enhance the corrosion, wear, and mechanical properties of aluminum alloys. Generally speaking, the anodic oxide film on aluminum alloys consists of an inner barrier layer and an outer porous layer. The composition of this anodic oxide film necessitates a subsequent sealing treatment. The quality of this sealing treatment often determines the ultimate performance and cost of the aluminum alloy. The sealing techniques currently used are mainly divided into high-pressure steam sealing, boiling water sealing, nickel salt sealing, cold nickel fluoride sealing, and hexavalent chromium sealing. During actual use, the anodic oxide film and the sealing layer structure can be damaged by bumps and impacts, which can cause discoloration and corrosion at the damaged areas, seriously affecting the performance and lifespan of the aluminum alloy.

[0003] Therefore, developing an aluminum alloy anodized film sealing technology that can self-heal under conditions of structural damage to prevent further corrosion of the aluminum alloy substrate without seriously affecting the performance and life of the aluminum alloy has become one of the current research hotspots in the field of aluminum alloy sealing technology.

[0004] Chinese patent CN119877057A (publication date April 25, 2025) discloses an aluminum alloy surface and its treatment method. The invention mainly includes four steps: surface cleaning of the aluminum alloy, chemical pretreatment, pulse anodization, and sealing treatment. The sealing self-healing effect is mainly reflected in the following aspects: the cerium complex releases Ce when exposed to an oxidizing environment for a long time. 3+ , and it will migrate to the damaged area, eventually forming oxide deposition, which can actively repair the damaged area and delay corrosion; but its main disadvantages are: 1) Ultrasonic assistance is required in the sealing stage, which not only increases the difficulty of operation and production cost, but also has no practical feasibility in actual production activities; 2) It cannot ensure that nano zinc oxide can effectively fill the micropores of the pulse anodized film, and then show the difference with Ce 3+ Double sealing effect.

[0005] Chinese patent CN101275265A (published on October 1, 2008) discloses a method for depositing a cerium-containing compound in an anodic oxide film of aluminum and its alloys. The invention mainly includes four steps: pre-treatment of the aluminum and its alloy surface, anodic oxidation, AC deposition of a cerium-containing compound, and sealing treatment. The main step is to add an AC deposition step of a cerium-containing compound before the sealing process, and to pass Ce 3+ or Ce 4+ The invention has simple process, convenient operation and low investment, and can be used to add a low-voltage AC power supply to the existing oxidation process workshop; however, its main disadvantages are: 1) the use of oxidants to promote Ce 3+ To Ce 4+ 2) Using AC process during cerium salt deposition to increase the bonding strength between it and the substrate oxide film will limit the scale and operability of actual production. Summary of the Invention

[0006] The purpose of the present invention is to provide a self-healing closed coating concentrate and a preparation method and application thereof, so as to solve the deficiencies of the prior art.

[0007] The present invention adopts the following technical solutions: A self-healing sealing coating concentrate, comprising a first-class complexing agent, a second-class complexing agent, a soluble cerium salt, a pH buffer, a wetting agent, and deionized water; The complexing agent includes one or more of propionic acid and its salts, lactic acid and its salts, glycine and its salts, malic acid and its salts, tartaric acid and its salts, and acetic acid and its salts; The second type of complexing agent includes one or both of asparagine and glutamine; The soluble cerium salt is one or more of cerium trichloride, cerium triiodide, cerium carbonate, cerium acetate, and cerium phosphate; The pH buffer is one or more of ammonium oxalate, phosphate buffer, and ammonium phthalate; The wetting agent is one or more of phosphate betaine type, sulfonyl betaine type, and carboxylic acid betaine type; The mass ratio of the first-class complexing agent, the second-class complexing agent, the soluble cerium salt, the pH buffer agent and the wetting agent is 10-25:20-30:25-55:15-20:3-10, and the balance is deionized water.

[0008] The method for preparing the above-mentioned self-healing sealing coating concentrate comprises the following steps: (1) Weigh each component according to the formula and dissolve each component into a transparent solution with appropriate amount of deionized water; (2) mixing a complexing agent solution with a soluble cerium salt solution and continuously stirring until a homogeneous phase is obtained to obtain a mixed solution; (3) Adding the pH buffer solution and the wetting agent solution to the mixed solution obtained in step (2) under stirring and continuing stirring until the mixed solution is homogeneous, and adjusting the pH of the mixed solution to 7.5-9.0 using ammonia water; (4) Add the second type complexing agent solution to the mixed solution obtained in step (3) under stirring conditions and continue stirring until the mixed solution is homogeneous, and adjust the pH of the mixed solution to 7.5-9.0 using ammonia water.

[0009] The application of the above self-healing sealing coating concentrate in sealing the pores of aluminum alloy anodized film.

[0010] Furthermore, when applied, the following steps are included: (1) Surface pretreatment: a) Degreasing and alkali etching: Place the aluminum alloy substrate into the degreasing and alkali etching solution for degreasing and alkali etching, then take it out and wash it with water; b) Stain removal: Place the aluminum alloy substrate after degreasing and alkali etching into the stain removal solution for stain removal, then take it out and rinse it with water; (2) Anodizing: Place the aluminum alloy substrate after surface pretreatment into an anodizing solution for anodizing, and then take it out and wash it with water; (3) Dyeing: Place the anodized aluminum alloy substrate into the dyeing solution for dyeing, and then take it out and wash it with water; (4) Sealing: The dyed aluminum alloy substrate is placed in a sealing solution for sealing, and then taken out for washing and drying; wherein the sealing solution comprises 80 to 120 ml / l of the self-healing sealing coating concentrate, and the remainder is deionized water; during operation, ammonia water is used to adjust the pH of the sealing solution to 7.5 to 9.0; the working temperature of the sealing solution is 25 to 50°C, and the working time is 15 to 30 minutes.

[0011] Furthermore, in step (1), the degreasing alkali etching solution includes 40-55 g / l NaOH, 30-35 g / l Na2CO3, 18-30 g / l NaHCO3, 25-35 g / l NaH2PO4, 3-8 g / l Tween-60, 25-35 g / l Na2SiO3, and the balance is deionized water; during operation, 200 g / l-250 g / l NaOH solution is used to adjust the pH of the degreasing alkali etching solution to 8.0-9.5; the working temperature of the degreasing alkali etching solution is 55-60°C, and the working time is 5-10 min.

[0012] Furthermore, in step (1), the stain removal solution includes 65-80 ml / l 98 wt% H2SO4, 5-12 ml / l 40 w / v% HF, and the balance is deionized water; the working temperature of the stain removal solution is 25-35°C, and the working time is 60-90 seconds.

[0013] Furthermore, in step (2), the anodizing solution includes 30-45 ml / l 98 wt% H2SO4, 35-50 g / l tartaric acid, and the balance is deionized water; the operating temperature of the anodizing solution is 10-55°C, the DC power supply is 15-30 V, and the operating time is 60-90 min.

[0014] Furthermore, the thickness of the anodic oxide film obtained by anodic oxidation is 20 to 35 μm.

[0015] Furthermore, in step (3), the dyeing solution includes 1 to 25 g / l of color powder (the specific color can be purchased according to the corresponding requirements), and the balance is deionized water; the working temperature of the dyeing solution is 35 to 50° C., and the working time is 10 to 30 minutes.

[0016] Furthermore, in step (4), drying is performed using a high-pressure air gun, and the pressure of the high-pressure air gun is 1.0 to 2.5 MPa.

[0017] Beneficial effects of the present invention:

[0018] 1. The sealing coating obtained based on the self-healing sealing coating concentrate of the present invention not only has excellent compactness but also exhibits excellent self-healing properties. Furthermore, the preparation and application of the self-healing sealing coating concentrate of the present invention are simple, low-cost, and environmentally friendly.

[0019] 2. The sealing coating obtained based on the self-healing sealing coating concentrate of the present invention avoids special process flows such as repeated sealing processes and electrolysis process flows, and achieves the purpose of generating strong bonding with the anodic oxide film through a type of complexing agent (one end of a type of complexing agent is complexed with cerium salt ions, and the other end forms a metallic bond with the anodic oxide film, thereby ensuring strong bonding between the sealing coating and the anodic oxide film).

[0020] 3. When the self-healing sealing coating concentrate of the present invention is used, it is combined with tartaric acid in the anodic oxidation solution (mainly used to control the pore size of the porous layer of the anodic oxidation film) to ensure that Ce 3+ Smoothly enter and generate oxides or hydroxides for filling (ensuring that the pore size of the porous layer of the anodic oxide film is adjustable, that is, ensuring that the Ce that has been combined with a type of complexing agent is 3+ can enter the porous layer).

[0021] 4. When the self-healing sealing coating concentrate of the present invention is used, Ce2O3 and Ce(OH)3 will first be generated in the porous layer of the anodic oxide film to fill the porous layer. Secondly, as the reaction proceeds, the sealing liquid will also form a sealing coating on the surface of the anodic oxide film (avoiding the use of oxidants such as hydrogen peroxide, through the electron-withdrawing effect of the amide group of the second type of complexing agent, Ce2O3 and Ce(OH)3 will be generated in the porous layer to fill the porous layer. 3+ The electron cloud in the amide group is biased towards the amide group, promoting the Ce 3+ To Ce 4+ By utilizing the fact that the solubility of Ce(OH)4 is lower than that of Ce(OH)3, Ce(OH)4 forms a closed coating on the surface of the anodic oxide film, thereby achieving double protection for the aluminum alloy substrate.

[0022] 5. The sealing coating obtained based on the self-healing sealing coating concentrate of the present invention has excellent self-healing properties in an alkaline environment. That is, even if the structure of the sealing coating is damaged, it can spontaneously repair itself in a short period of time without external influence, providing an effective guarantee for improving the corrosion resistance of the aluminum alloy anodic oxide film. The self-healing principle of the sealing coating of the present invention is as follows: 2Ce(OH)3→Ce2O3+3H2O (1) 4Ce 3+ +O2+12OH - +2H2O→4Ce(OH)4 (2) Ce(OH)4→CeO2+2H2O (3) When the aluminum alloy substrate is pierced by a scratch, the Ce(OH)3 inside is exposed and reacts (1) to release trivalent cerium ions (Ce 3+ ), the trivalent cerium ion (Ce 3+ ) will further react with hydroxide to generate Ce(OH)4, part of which will then transform into CeO2. Therefore, the new sealing coating composed of Ce(OH)4 and CeO2 will once again seal the exposed aluminum alloy substrate, which is a self-healing sealing effect. DETAILED DESCRIPTION

[0023] The present invention will be further explained below in conjunction with the examples. The following examples are only used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0024] The ammonia water mentioned below refers to industrial ammonia water, which is an aqueous solution containing 25wt% to 28wt% ammonia.

[0025] The test pieces of each of the following examples were tested for corrosion resistance according to the neutral salt spray test (NSS) in GB / T 12967.3-2022 “Aluminium and aluminium alloys - Methods for examination of anodic oxidation and organic polymer films - Part 3: Salt spray test”, the copper-accelerated acetic acid salt spray test (CASS), the test for sealing quality according to the sodium molybdate-phosphoric acid method in GB / T 8753.1-2017 “Aluminium and aluminium alloys - Methods for examination of anodic oxidation films - Part 1: Sealing quality - Acid immersion weight loss method”, and the uniform corrosion immersion test method for metal materials laboratories in JB / T 7901-2023, i.e. using a craft knife to make a scratch on the anodized aluminium alloy that has been sealed by the self-healing sealing coating, and making the scratch directly to the aluminium alloy substrate (i.e. through the anodic oxidation film), then immersing the test piece in a 3.5wt% NaCl solution of different pH (adjusted using 250g / l NaOH solution) for different times (12h, 24h, 48h, 72h, 96h and 120h), and then checking whether the scratch is automatically repaired and whether the test piece is corroded, wherein the 3.5wt% NaCl solution is replaced every day, and the pH needs to be re-adjusted and confirmed; the pH values of the 3.5wt% NaCl solution corresponding to Example 1, Example 2 and Example 3 are 8.5, 7.5 and 9.0 respectively.

[0026] The degreasing and caustic etching solution in each example includes 45g / l NaOH, 32g / l Na2CO3, 25g / l NaHCO3, 30g / l NaH2PO4, 5g / l Tween-60, 30g / l Na2SiO3, and the balance is deionized water; the stain removal solution includes 70ml / l 98wt% H2SO4, 8ml / l 40w / v% HF, and the balance is deionized water; the anodizing solution includes 40ml / l 98wt% H2SO4, 45g / l tartaric acid, and the balance is deionized water.

[0027] Example 1

[0028] The self-healing sealing coating concentrate in this example includes 18g / l propionic acid, 25g / l asparagine, 40g / l cerium trichloride, 18g / l ammonium oxalate and 6g / l sulfobetaine-12, and the balance is deionized water.

[0029] The preparation process of the self-healing sealing coating concentrate is as follows: weigh each component according to the above formula, and dissolve each component into a transparent solution with an appropriate amount of deionized water; first, mix the propionic acid solution and the cerium trichloride solution and continue stirring until they are homogeneous, then add the ammonium oxalate solution and the sulfobetaine-12 solution under stirring conditions and continue stirring until they are homogeneous, and use ammonia water to adjust the pH of the mixed solution to 8.0; finally, add the asparagine solution under stirring conditions and continue stirring until they are homogeneous, and use ammonia water again to adjust the pH of the mixed solution to 8.0 for use.

[0030] (1) Degreasing and alkali etching: Place the aluminum alloy substrate in a degreasing and alkali etching solution at 60°C and pH 8.5 (adjust the pH with 250g / l NaOH solution) for 5 minutes for degreasing and alkali etching, then take it out and wash it with water for later use; (2) Destaining: Place the aluminum alloy substrate after degreasing and alkali etching in a destaining solution at 35°C for 60 seconds to remove stains, then take it out and wash it with water for later use; (3) Anodizing: The aluminum alloy substrate after stain removal was placed in an anodizing solution at 45°C for 85 minutes, and a DC power supply was used to apply a voltage of 15V to it for anodizing. The substrate was then taken out for washing and set aside. The thickness of the anodized film obtained was 26 μm. (4) Dyeing: Place the anodized aluminum alloy substrate in a solution containing 8 g / l color powder (ODM DYE ORANGE (OR214) from Hangzhou Heyun Technology Co., Ltd.) at 45°C for 30 min for dyeing, then take it out, wash it with water, and set aside; (5) Sealing: Place the dyed aluminum alloy substrate in a sealing solution at 50°C, containing 100 ml / l of self-healing sealing coating concentrate and a pH of 8.0 (pH adjusted with ammonia water) for 25 minutes for sealing. Then take it out, wash it with water, and blow it dry with a high-pressure air gun (1.5 MPa).

[0031] Example 2

[0032] The self-healing sealing coating concentrate in this embodiment includes 25 g / l glycine, 30 g / l glutamine, 55 g / l cerium acetate, 20 g / l ammonium phthalate and 10 g / l dodecyl dimethyl betaine, with the balance being deionized water.

[0033] The preparation process of the self-healing sealing coating concentrate is as follows: weigh each component according to the above formula, and dissolve each component into a transparent solution with an appropriate amount of deionized water; first, mix the glycine solution and the cerium acetate solution and continue stirring until they are homogeneous, then add the ammonium phthalate solution and the dodecyl dimethyl betaine solution under stirring conditions and continue stirring until they are homogeneous, and use ammonia water to adjust the pH of the mixed solution to 9.0; finally, add the glutamine solution under stirring conditions and continue stirring until they are homogeneous, and use ammonia water again to adjust the pH of the mixed solution to 9.0 for later use.

[0034] (1) Degreasing and alkali etching: Place the aluminum alloy substrate in a degreasing and alkali etching solution at 60°C and pH 8.5 (adjust the pH with 250g / l NaOH solution) for 8 minutes for degreasing and alkali etching, then take it out and wash it with water for later use; (2) Destaining: Place the aluminum alloy substrate after degreasing and alkali etching in a destaining solution at 35°C for 80 seconds to remove stains, then take it out and wash it with water for later use; (3) Anodizing: The aluminum alloy substrate after stain removal was placed in an anodizing solution at 45°C for 90 minutes, and a DC power supply was used to apply an 18V voltage to the substrate for anodizing. The substrate was then taken out for washing and set aside. The thickness of the anodized film obtained was 30 μm. (4) Dyeing: Place the anodized aluminum alloy substrate in a solution containing 10 g / l color powder (ODM DYE BROWN (BN615) produced by Hangzhou Heyun Technology Co., Ltd.) at 50°C for 15 minutes for dyeing, then take it out, wash it with water, and set aside; (5) Sealing: Place the dyed aluminum alloy substrate in a sealing solution at 45°C, containing 80 ml / l of self-healing sealing coating concentrate and a pH of 9.0 (adjust the pH with ammonia water) for 30 minutes for sealing. Then take it out, wash it with water, and then blow it dry with a high-pressure air gun (1.5 MPa).

[0035] Example 3

[0036] The self-healing sealing coating concentrate in this embodiment includes 10 g / l tartaric acid, 15 g / l glutamine, 15 g / l asparagine, 30 g / l cerium carbonate, 20 g / l ammonium phthalate and 5 g / l tetradecyl hydroxypropyl betaine phosphate, and the balance is deionized water.

[0037] The preparation procedure of the self-healing sealing coating concentrate is as follows: each component is weighed according to the above formula, and each component is dissolved into a transparent solution with deionized water; first, the tartaric acid solution and the cerium carbonate solution are mixed and continuously stirred until homogeneous, then the ammonium phthalate solution and the tetradecyl hydroxypropyl phosphatidyl betaine solution are added under stirring and continuously stirred until homogeneous, and the pH of the mixed solution is adjusted to 7.5 using ammonia water; finally, the glutamine solution and the asparagine solution are added under stirring and continuously stirred until homogeneous, and the pH of the mixed solution is adjusted to 7.5 using ammonia water again, and is ready for use.

[0038] (1) Oil and alkali removal: the aluminum alloy substrate is placed in an oil and alkali removal solution at 60°C and pH 9.0 (pH is adjusted by 250 g / l NaOH solution) for 5 min for oil and alkali removal, then taken out and washed with water, and is ready for use; (2) Stain removal: the aluminum alloy substrate after oil and alkali removal is placed in a stain removal solution at 30°C for 70 s for stain removal, then taken out and washed with water, and is ready for use; (3) Anodizing: the aluminum alloy substrate after stain removal is placed in an anodizing solution at 55°C for 80 min, and a voltage of 22V is applied to it at the same time using a direct current power supply for anodizing, then taken out and washed with water, and is ready for use; wherein the thickness of the anodizing film obtained is 24 μm; (4) Dyeing: the aluminum alloy substrate after anodizing is placed in a solution containing 5 g / l color powder (Hangzhou Heyun Technology Co., Ltd. ODM DYE YELLOW (YW3105)) at 50°C for 20 min for dyeing, then taken out and washed with water, and is ready for use; (5) Sealing: the aluminum alloy substrate after dyeing is placed in a sealing solution containing 120 ml / l self-healing sealing coating concentrate at 45°C and pH 7.5 (pH is adjusted by ammonia water) for 30 min for sealing, then taken out and washed with water, and is ready for use using a high-pressure air gun (1.5 MPa).

[0039] The performance of the parts obtained in each example is tested, and the test results are shown in the following table: Neutral Salt Spray Test (NSS) Copper Accelerated Acetic Acid Salt Spray Test (CASS) Acid etching weight loss method-sodium molybdate phosphate method Self-healing performance Example 1 Level 10 Level 10 <![CDATA[0mg / dm 2 ]]> The scratches were initially healed after 12 hours and completely healed after 72 hours without any corrosion. Example 2 Level 10 Level 10 0 mg / dm 2 ]] The scratches were initially healed after 12 hours and completely healed after 24 hours without any corrosion. Example 3 Level 10 Level 10 <![CDATA[0mg / dm 2 ]]> After 12 hours, the scratches are completely healed and there is no corrosion.

Claims

1. A self-healing closed coating concentrate, characterized in that: The self-healing sealing coating concentrate comprises a first-class complexing agent, a second-class complexing agent, a soluble cerium salt, a pH buffer, a wetting agent and deionized water; The complexing agent includes one or more of propionic acid and its salts, lactic acid and its salts, glycine and its salts, malic acid and its salts, tartaric acid and its salts, and acetic acid and its salts; The second type of complexing agent includes one or both of asparagine and glutamine; The soluble cerium salt is one or more of cerium trichloride, cerium triiodide, cerium carbonate, cerium acetate, and cerium phosphate; The pH buffer is one or more of ammonium oxalate, phosphate buffer, and ammonium phthalate; The wetting agent is one or more of phosphate betaine type, sulfonyl betaine type, and carboxylic acid betaine type; The mass ratio of the first-class complexing agent, the second-class complexing agent, the soluble cerium salt, the pH buffer agent and the wetting agent is 10-25:20-30:25-55:15-20:3-10, and the balance is deionized water.

2. The method for preparing a self-healing sealing coating concentrate according to claim 1, characterized in that: The following steps are involved: (1) Weigh each component according to the formula and dissolve each component into a transparent solution with appropriate amount of deionized water; (2) mixing a complexing agent solution with a soluble cerium salt solution and continuously stirring until a homogeneous phase is obtained to obtain a mixed solution; (3) Adding the pH buffer solution and the wetting agent solution to the mixed solution obtained in step (2) under stirring and continuing stirring until the mixed solution is homogeneous, and adjusting the pH of the mixed solution to 7.5-9.0 using ammonia water; (4) Add the second type complexing agent solution to the mixed solution obtained in step (3) under stirring conditions and continue stirring until the mixed solution is homogeneous, and adjust the pH of the mixed solution to 7.5-9.0 using ammonia water.

3. Use of the self-healing sealing coating concentrate according to claim 1 in sealing pores of anodized aluminum alloy films.

4. The use according to claim 3, characterized in that When applied, the following steps are involved: (1) Surface pretreatment: a) Degreasing and alkali etching: Place the aluminum alloy substrate into the degreasing and alkali etching solution for degreasing and alkali etching, then take it out and wash it with water; b) Stain removal: Place the aluminum alloy substrate after degreasing and alkali etching into the stain removal solution for stain removal, then take it out and rinse it with water; (2) Anodizing: Place the aluminum alloy substrate after surface pretreatment into an anodizing solution for anodizing, and then take it out and wash it with water; (3) Dyeing: Place the anodized aluminum alloy substrate into the dyeing solution for dyeing, and then take it out and wash it with water; (4) Sealing: The dyed aluminum alloy substrate is placed in a sealing solution for sealing, and then taken out for washing and drying; wherein the sealing solution comprises 80 to 120 ml / l of the self-healing sealing coating concentrate, and the remainder is deionized water; during operation, ammonia water is used to adjust the pH of the sealing solution to 7.5 to 9.0; the working temperature of the sealing solution is 25 to 50°C, and the working time is 15 to 30 minutes.

5. The use according to claim 4, characterized in that In step (1), the degreasing alkali etching solution includes 40-55 g / l NaOH, 30-35 g / l Na2CO3, 18-30 g / l NaHCO3, 25-35 g / l NaH2PO4, 3-8 g / l Tween-60, 25-35 g / l Na2SiO3, and the balance is deionized water; during operation, 200 g / l-250 g / l NaOH solution is used to adjust the pH of the degreasing alkali etching solution to 8.0-9.5; the working temperature of the degreasing alkali etching solution is 55-60°C, and the working time is 5-10 min.

6. The use according to claim 4, characterized in that In step (1), the stain removal solution includes 65-80 ml / l 98 wt% H2SO4, 5-12 ml / l 40 w / v% HF, and the balance is deionized water; the working temperature of the stain removal solution is 25-35°C, and the working time is 60-90 seconds.

7. The use according to claim 4, characterized in that In step (2), the anodizing solution includes 30-45 ml / l 98 wt% H2SO4, 35-50 g / l tartaric acid, and the balance is deionized water; the operating temperature of the anodizing solution is 10-55°C, the DC power supply is 15-30 V, and the operating time is 60-90 min.

8. The use according to claim 7, characterized in that The thickness of the anodic oxide film obtained by anodic oxidation is 20 to 35 μm.

9. The use according to claim 4, characterized in that In step (3), the dyeing solution includes 1 to 25 g / l of color powder, and the balance is deionized water; the working temperature of the dyeing solution is 35 to 50° C., and the working time is 10 to 30 minutes.

10. The use according to claim 4, characterized in that In step (4), drying is performed using a high-pressure air gun, and the pressure of the high-pressure air gun is 1.0 to 2.5 MPa.