Aluminum alloy composite anode oxide film and preparation method thereof

Abstract

The preparation method comprises the following steps that S1, an anodic oxidation base film is formed, specifically, an aluminum alloy workpiece subjected to surface treatment is subjected to anodic oxidation, the anodic oxidation base film with an anchoring groove is formed on the surface of the aluminum alloy workpiece, and the anodic oxidation base film is dried for standby application after being washed with water; s2, electrostatic powder spraying, melting and composite film forming: performing electrostatic powder spraying on the anodic oxidation base film obtained in the step S1 by taking polytetrafluoroethylene powder as a raw material, heating the aluminum alloy workpiece after spraying is completed, melting the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece into a film, and naturally cooling to obtain the composite film. A composite film formed by compounding the anodic oxidation base film and polytetrafluoroethylene is obtained; and S3, magnetic control polishing is conducted, specifically, the composite film on the surface of the aluminum alloy workpiece in the S2 is polished and leveled through magneto-rheological polishing liquid, and then the aluminum alloy workpiece is obtained. The aluminum alloy composite anode oxide film prepared through the method has good abrasion resistance and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy surface treatment technology, specifically to an aluminum alloy anodic oxide film and its preparation method. Background Technology

[0002] Aluminum and aluminum alloy parts are widely used in the manufacturing and processing of building materials, industrial equipment, and electronic product components due to their lightweight, high strength, and good machinability. Aluminum and aluminum alloys are chemically reactive and easily oxidized and corroded; however, the formation of a high-quality, dense oxide film on their surface ensures excellent corrosion resistance. Therefore, aluminum and aluminum alloy parts typically undergo anodizing after forming to create a corrosion-resistant, dense oxide film. The anodized film formed by simple anodizing has a highly porous surface, making it prone to accumulating dirt and corrosive substances. Therefore, further post-treatment (such as sealing with a pore sealant or heat sealing) is currently required after anodizing to enhance the corrosion resistance of the surface oxide film.

[0003] In certain applications, aluminum and aluminum alloy workpieces also require a certain degree of wear resistance. Simple sealing agents or heat-sealing processes for aluminum alloy anodizing films typically only guarantee corrosion resistance, not wear resistance. Therefore, it is necessary to research and develop a composite anodizing film that simultaneously possesses excellent wear resistance and corrosion resistance. Summary of the Invention

[0004] This invention provides an aluminum alloy anodic oxide film and its preparation method, aiming to solve the shortcomings of existing aluminum alloy anodic oxide films that cannot simultaneously possess good wear resistance and corrosion resistance.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing an aluminum alloy composite anodic oxide film, comprising the following steps:

[0006] S1. Anodized base film formation: The surface-treated aluminum alloy workpiece is anodized to form an anodized base film with anchoring grooves on the surface of the aluminum alloy workpiece. After washing with water, it is dried and ready for use.

[0007] S2. Electrostatic powder spraying and melting composite film formation: The anodic oxide base film obtained in S1 is electrostatically powder sprayed with polytetrafluoroethylene powder as raw material. After the spraying is completed, the aluminum alloy workpiece is heated so that the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece melts into a film. After natural cooling, a composite film of anodic oxide base film and polytetrafluoroethylene is obtained.

[0008] S3. Magnetron Polishing: The composite film on the surface of the aluminum alloy workpiece in S2 is polished and leveled using magnetorheological polishing fluid.

[0009] Based on the above technical solutions, the present invention may also have the following further specific options.

[0010] Specifically, in S1, the surface of the aluminum alloy workpiece is first chemically etched to form an anchoring groove. After being cleaned and dried, it is placed as an anode in a mixed electrolyte solution composed of citric acid aqueous solution and anhydrous ethanol. Under ultrasonic action, anodizing is performed once. Then, the aluminum alloy workpiece is taken out and immersed in phosphoric acid solution. Under ultrasonic action, the hole is enlarged. Finally, it is placed as an anode again in the mixed electrolyte solution. Under ultrasonic action, anodizing is performed twice, thus forming an anodized base film with anchoring grooves.

[0011] Specifically, hydrochloric acid or sodium hydroxide solution is used for chemical etching, and the depth of the anchoring groove is 0.25-0.75 mm.

[0012] Specifically, the anchoring groove is a long, longitudinal, transverse, or crisscrossing strip-shaped channel formed on the wear-resistant surface of the aluminum alloy workpiece, and the width of the channel is 0.5-1.5mm.

[0013] Specifically, the anchoring groove is a circular groove formed on the wear-resistant surface of the aluminum alloy workpiece in a dot-matrix pattern, the diameter of the circular groove is 1-2 mm, and the spacing between adjacent circular grooves is 5-10 mm.

[0014] Specifically, the mixed electrolyte is composed of 0.3-0.5 mol / L citric acid solution and anhydrous ethanol mixed at a volume ratio of 1:1.5. During both primary and secondary anodizing, the electrolysis voltage is controlled at 600-650V, the electrolysis temperature at 15-25℃, and the electrolysis time at 1-1.5h. Under ultrasonic treatment, the ultrasonic power is controlled at 140-180W and the ultrasonic frequency at 38-45kHz. The concentration of the phosphoric acid solution is 5wt%, and the aluminum alloy workpiece is immersed in the phosphoric acid solution for 15-20min.

[0015] Specifically, the polytetrafluoroethylene powder in S2 is an ultrafine powder with a particle size of less than 5μm. During electrostatic powder spraying, the electrostatic voltage is set to 75-92kV, the electrostatic current is set to 18-25μA, the fluidization pressure is 0.05-0.10MPa, and the powder spraying amount is 500-1200g / min.

[0016] Specifically, in S2, the surface temperature of the aluminum alloy workpiece after heating is 330-350℃.

[0017] Specifically, when the composite film is magnetorheologically polished and leveled using the magnetorheological polishing slurry in S3, the surface grinding removal thickness is controlled to be 5-20μm.

[0018] The present invention also provides an aluminum alloy composite anodic oxide film, which is prepared by the above method.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention first forms anchoring grooves on the surface of an aluminum alloy workpiece, and then uses an electrostatic powder coating process to spray polytetrafluoroethylene (PTFE) onto the workpiece surface and melt it into a composite film. In this composite film, the PTFE penetrates into the enlarged pores (micron-level) of the anodic oxide film on the workpiece surface, and simultaneously anchors to the anchoring grooves, ensuring that the PTFE, which provides corrosion protection and resistance, is firmly bonded to the anodic oxide base film. The anchoring grooves and enlarged pores of the anodic oxide base film in this invention greatly enhance the ability of the PTFE on the workpiece surface to resist shear stress peeling, ensuring that the workpiece with this composite anodic oxide film possesses excellent wear resistance and corrosion resistance. Attached Figure Description

[0021] Figure 1 This is a top view of the aluminum alloy workpiece after surface treatment in step S1 of Embodiment 1 of the present invention;

[0022] Figure 2 The aluminum alloy composite anodic oxide film prepared in Example 1 of this invention is shown along... Figure 1 A cross-sectional view along the AA direction (only the composite film on the upper surface is shown; composite films on other surfaces are not shown).

[0023] The attached diagram lists the components represented by each number as follows:

[0024] 1. Aluminum alloy workpiece; 2. Anodized base film; 3. Anchoring groove; 4. Polytetrafluoroethylene layer. Detailed Implementation

[0025] The technical solutions provided by the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To avoid unnecessary details, unless otherwise specified, all raw materials used in the following examples are commercially available products, and all methods used are conventional methods in the art.

[0027] The aluminum alloy workpieces used in the following examples are all 5mm thick and have an area of Represented by a rectangular aluminum alloy plate, the upper surface of which is an anti-wear surface. Before the anodized base film is formed, anchoring grooves are first formed on the surface of the aluminum alloy plate by chemical etching. The preferred method is to first form a protective layer (such as applying a PET protective film) on the anti-wear surface, and then physically cut or plasma etch the protective layer to form grooves corresponding to the anchoring grooves. Subsequently, hydrochloric acid or sodium hydroxide is injected into the grooves to etch the anti-wear surface below for a certain period of time to form anchoring grooves of a specific depth and width. Then, the protective layer is removed (such as peeling off the protective film), and then acetone, ethanol and deionized water are used to clean it in sequence. Finally, it is dried to obtain the surface-treated aluminum alloy workpiece.

[0028] Example 1

[0029] An aluminum alloy composite anodic oxide film is prepared by the following steps:

[0030] S1. Anodizing Base Film Forming: Anodizing is performed on the surface-treated aluminum alloy workpiece, wherein the anchoring groove of the surface-treated workpiece is as follows... Figure 1 The aluminum alloy workpiece, with its crisscrossing channels, is cleaned and dried before being placed as an anode in a mixed electrolyte solution of citric acid and anhydrous ethanol. Under ultrasonic treatment, it undergoes a first anodizing process. The workpiece is then removed and immersed in a phosphoric acid solution, where it is ultrasonically enlarged. Finally, it is placed back into the mixed electrolyte solution as an anode for a second anodizing process under ultrasonic treatment, thus forming an anodized base film with anchoring grooves. The mixed electrolyte solution consists of a 0.3 mol / L citric acid solution and anhydrous ethanol mixed at a volume ratio of 1:1.5. During both the first and second anodizing processes, the electrolysis voltage is controlled at 650V, the electrolysis temperature at 15℃, and the electrolysis time at 1 hour. Ultrasonic treatment refers to controlling the ultrasonic power at 140W and the ultrasonic frequency at 38kHz. The concentration of the phosphoric acid solution is 5 wt%, and the immersion time of the aluminum alloy workpiece in the phosphoric acid solution is 20 minutes. Each channel forming the anchoring groove on the anodized base film has a depth of 0.25 mm and a width of 1 mm. After washing and drying, the workpiece is ready for use.

[0031] S2. Electrostatic powder spraying and melting composite film formation: The anodic oxide base film obtained in S1 is electrostatically powder sprayed with polytetrafluoroethylene powder as raw material. During electrostatic powder spraying, the electrostatic voltage is set to 75kV, the electrostatic current is set to 18μA, the fluidization pressure is 0.05MPa, and the powder spraying amount is 800g / min. After the spraying is completed, the aluminum alloy workpiece is heated to a surface temperature of 340℃, which melts the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece into a film. After natural cooling, a composite film of anodic oxide base film and polytetrafluoroethylene is obtained.

[0032] S3. Magnetron Polishing: The composite film on the surface of the aluminum alloy workpiece in S2 is polished and leveled using magnetorheological polishing fluid. The polishing speed is controlled at 5000 r / min and the polishing time is controlled at 6 min.

[0033] A cross-sectional view of the aluminum alloy composite anodic oxide film obtained in this embodiment is shown below. Figure 2 As shown in the figure, only the formation of the composite film on the upper surface (wear-resistant surface) of the aluminum alloy workpiece is highlighted; the composite film on other surfaces is not shown. Figure 2 The labels in the figure represent the aluminum alloy workpiece 1, the anodized base film 2, the anchoring groove 3, and the polytetrafluoroethylene layer 4, respectively.

[0034] Example 2

[0035] An aluminum alloy composite anodic oxide film is prepared by the following steps:

[0036] S1. Anodizing Base Film Forming: Anodizing is performed on the surface-treated aluminum alloy workpiece, wherein the anchoring groove of the surface-treated workpiece is as follows... Figure 1 The crisscrossing channels shown are cleaned and dried, then used as anodes in a mixed electrolyte solution composed of citric acid aqueous solution and anhydrous ethanol. Under ultrasonic treatment, anodizing is performed once. The aluminum alloy workpiece is then removed and immersed in a phosphoric acid solution, where it undergoes pore-enlarging treatment under ultrasonic treatment. Finally, it is again used as anodes in the mixed electrolyte solution for a second anodizing under ultrasonic treatment, thus forming an anodized base film with anchoring grooves. The mixed electrolyte solution consists of 0.5 mol / L citric acid solution and anhydrous ethanol... The mixture is prepared at a volume ratio of 1:1.5. During both primary and secondary anodizing, the electrolysis voltage is controlled at 620V, the electrolysis temperature at 18℃, and the electrolysis time at 1.5h. Ultrasonic treatment refers to controlling the ultrasonic power at 160W and the ultrasonic frequency at 42kHz. The concentration of the phosphoric acid solution is 5wt%, and the aluminum alloy workpiece is immersed in the phosphoric acid solution for 16min. Each groove forming the anchoring groove on the anodized base film has a depth of 0.35mm and a width of 0.8mm. After washing with water, the workpiece is dried and ready for use.

[0037] S2. Electrostatic powder spraying and melting composite film formation: The anodic oxide base film obtained in S1 is electrostatically powder sprayed with polytetrafluoroethylene powder as raw material. During electrostatic powder spraying, the electrostatic voltage is set to 80kV, the electrostatic current is set to 20μA, the fluidization pressure is 0.06MPa, and the powder spraying amount is 1000g / min. After the spraying is completed, the aluminum alloy workpiece is heated to a surface temperature of 345℃, which melts the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece into a film. After natural cooling, a composite film of anodic oxide base film and polytetrafluoroethylene is obtained.

[0038] S3. Magnetron Polishing: The composite film on the surface of the aluminum alloy workpiece in S2 is polished and leveled using magnetorheological polishing fluid. The polishing speed is controlled at 5000 r / min and the polishing time is controlled at 5 min.

[0039] Example 3

[0040] An aluminum alloy composite anodic oxide film is prepared by the following steps:

[0041] S1. Anodizing Base Film Forming: Anodizing is performed on the surface-treated aluminum alloy workpiece, wherein the anchoring groove of the surface-treated workpiece is as follows... Figure 1 The crisscrossing channels shown are cleaned and dried, then used as anodes in a mixed electrolyte solution composed of citric acid aqueous solution and anhydrous ethanol. Under ultrasonic treatment, anodizing is performed first. The aluminum alloy workpiece is then removed and immersed in a phosphoric acid solution, where it undergoes pore-enlarging treatment under ultrasonic treatment. Finally, it is again used as anodes in the mixed electrolyte solution for a second anodizing under ultrasonic treatment, thus forming an anodized base film with anchoring grooves. The mixed electrolyte solution consists of 0.4 mol / L citric acid solution and anhydrous ethanol... The mixture is prepared at a volume ratio of 1:1.5. During both primary and secondary anodizing, the electrolysis voltage is controlled at 630V, the electrolysis temperature at 21℃, and the electrolysis time at 1.2h. Ultrasonic treatment refers to controlling the ultrasonic power at 150W and the ultrasonic frequency at 40kHz. The concentration of the phosphoric acid solution is 5wt%, and the aluminum alloy workpiece is immersed in the phosphoric acid solution for 15min. Each groove forming the anchoring groove on the anodized base film has a depth of 0.45mm and a width of 1.2mm. After washing with water, the workpiece is dried and ready for use.

[0042] S2. Electrostatic powder spraying and melting composite film formation: The anodic oxide base film obtained in S1 is electrostatically powder sprayed with polytetrafluoroethylene powder as raw material. During electrostatic powder spraying, the electrostatic voltage is set to 85kV, the electrostatic current is set to 23μA, the fluidization pressure is 0.07MPa, and the powder spraying amount is 1000g / min. After the spraying is completed, the aluminum alloy workpiece is heated to a surface temperature of 350℃, so that the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece melts and forms a film. After natural cooling, a composite film of anodic oxide base film and polytetrafluoroethylene is obtained.

[0043] S3. Magnetron Polishing: The composite film on the surface of the aluminum alloy workpiece in S2 is polished and leveled using magnetorheological polishing fluid. The polishing speed is controlled at 6000 r / min and the polishing time is controlled at 3 min.

[0044] Example 4

[0045] An aluminum alloy composite anodic oxide film is prepared by the following steps:

[0046] S1. Anodizing Base Film Forming: Anodizing is performed on the surface-treated aluminum alloy workpiece, wherein the anchoring groove of the surface-treated workpiece is as follows... Figure 1 The crisscrossing channels shown are cleaned and dried, then used as anodes in a mixed electrolyte solution composed of citric acid aqueous solution and anhydrous ethanol. Under ultrasonic treatment, anodizing is performed once. The aluminum alloy workpiece is then removed and immersed in a phosphoric acid solution, where it undergoes pore-enlarging treatment under ultrasonic treatment. Finally, it is again used as anodes in the mixed electrolyte solution for a second anodizing under ultrasonic treatment, thus forming an anodized base film with anchoring grooves. The mixed electrolyte solution consists of 0.3 mol / L citric acid solution and anhydrous ethanol... The mixture is prepared at a volume ratio of 1:1.5. During both primary and secondary anodizing, the electrolysis voltage is controlled at 600V, the electrolysis temperature at 25℃, and the electrolysis time at 1.5h. Ultrasonic treatment refers to controlling the ultrasonic power at 180W and the ultrasonic frequency at 38kHz. The concentration of the phosphoric acid solution is 5wt%, and the aluminum alloy workpiece is immersed in the phosphoric acid solution for 20min. Each groove forming the anchoring groove on the anodized base film has a depth of 0.55mm and a width of 1.5mm. After washing with water, the workpiece is dried and ready for use.

[0047] S2. Electrostatic powder spraying and melting composite film formation: The anodic oxide base film obtained in S1 is electrostatically powder sprayed with polytetrafluoroethylene powder as raw material. During electrostatic powder spraying, the electrostatic voltage is set to 92kV, the electrostatic current is set to 25μA, the fluidization pressure is 0.08MPa, and the powder spraying amount is 1200g / min. After the spraying is completed, the aluminum alloy workpiece is heated to a surface temperature of 350℃, so that the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece melts and forms a film. After natural cooling, a composite film of anodic oxide base film and polytetrafluoroethylene is obtained.

[0048] S3. Magnetron Polishing: The composite film on the surface of the aluminum alloy workpiece in S2 is polished and leveled using magnetorheological polishing fluid. The polishing speed is controlled at 6000 r / min and the polishing time is controlled at 3 min.

[0049] Comparative Example 1

[0050] Compared with Example 1, the only difference is that the aluminum alloy workpiece surface in this comparative example does not have anchoring grooves.

[0051] Comparative Example 2

[0052] Compared with Example 1, the only difference is that ultrasonic action was not used when the aluminum alloy workpiece was anodized in this comparative example (i.e., there was no ultrasonic action to help expand the porosity of the anodized film).

[0053] Testing revealed that the anodic oxide base film on the surface of the aluminum alloy workpiece after anodizing treatment in step S1 of Examples 1 to 4 of this invention has significantly larger pores than conventional aluminum alloy anodic oxide films. The average pore diameter is above 1.5 μm, and the pore depth is between 8 and 12 μm. The increased pore diameter and suitable pore depth facilitate the anchoring of the molten film layer formed by polytetrafluoroethylene (PTFE) micropowder during electrostatic powder spraying into the pores of the base film to a greater extent, ensuring a stable bond between the PTFE micropowder and the anodic oxide base film to form a composite film. The average thickness of the PTFE layer in the aluminum alloy composite anodic oxide films formed in Examples 1 to 4 is 60-120 μm. The surface friction coefficient of the aluminum alloy composite anodized films obtained in each embodiment and comparative example was found to be below 0.1, indicating extremely low friction coefficient. Subsequently, wear resistance tests were conducted on the aluminum alloy composite anodized films obtained in each embodiment and comparative example, and friction and wear tests (ASTM G77-16) were performed on the wear-resistant surfaces of the aluminum alloy. Examples 1 to 4 all showed good wear resistance with no obvious wear, while Comparative Example 1 and Comparative Example 2 showed poor wear resistance, and the surface polytetrafluoroethylene layer peeled off during the test.

[0054] The present invention also conducted corrosion resistance tests on the aluminum alloy composite anodized films obtained in Examples 1 to 4, comparing them with aluminum alloy anodized films treated with conventional commercially available sealing agents. The results showed that the aluminum alloy composite anodized films obtained in each example of the present invention exhibited superior corrosion resistance in terms of acid resistance, alkali resistance, and abrasion resistance.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an aluminum alloy composite anodic oxide film, characterized in that, It comprises the following steps: S1. Anodic oxidation base film forming: anodizing the surface treated aluminum alloy workpiece to form an anodic oxidation base film with anchor grooves on the surface of the aluminum alloy workpiece, washing with water, drying, and reserving; S2. Electrostatic powder spraying and melting composite film forming: electrostatic powder spraying the anodic oxidation base film obtained in S1 with polytetrafluoroethylene powder as raw material, heating the aluminum alloy workpiece after spraying to melt the polytetrafluoroethylene powder adsorbed on the surface of the aluminum alloy workpiece into a film, and naturally cooling to obtain a composite film of the anodic oxidation base film and polytetrafluoroethylene; S3. Magnetic control polishing: using a magnetic rheological polishing liquid to polish and flatten the composite film on the surface of the aluminum alloy workpiece in S2, and obtaining the same.

2. The method of claim 1, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a transition metal salt. In S1, the surface of the aluminum alloy workpiece is first subjected to chemical etching treatment to form anchor grooves, and after washing and drying, it is used as an anode to be put into a mixed electrolyte composed of a citric acid aqueous solution and anhydrous ethanol, and under the action of ultrasonic waves, it is subjected to primary anodization by passing electricity, then the aluminum alloy workpiece is taken out and immersed in a phosphoric acid solution, and under the action of ultrasonic waves, it is subjected to hole expansion treatment, and finally it is used as an anode again to be put into the mixed electrolyte, and under the action of ultrasonic waves, it is subjected to secondary anodization by passing electricity, thereby forming an anodic oxidation base film with anchor grooves.

3. The method of claim 2, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. The hydrochloric acid solution or sodium hydroxide solution used in chemical etching is used, and the groove depth of the anchor grooves is 0.25-0.75 mm.

4. The method of claim 3, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. The anchor grooves are longitudinal, transverse or longitudinal and transverse intersecting long strip-shaped grooves formed on the wear-resistant surface of the aluminum alloy workpiece, and the width of the grooves is 0.5-1.5 mm.

5. The method of claim 3, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. The anchor grooves are circular grooves arranged in a dot matrix pattern and spaced apart, and the diameter of the circular grooves is 1-2 mm, and the spacing between adjacent circular grooves is 5-10 mm.

6. The method of claim 2, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. The mixed electrolyte is prepared by mixing 0.3-0.5 mol / L citric acid solution and anhydrous ethanol in a volume ratio of 1:1.5, and the electrolytic voltage is controlled at 600-650 V during primary anodization and secondary anodization, the electrolytic temperature is 15-25℃, and the electrolytic time is 1-1.5 h; under the action of ultrasonic waves, the ultrasonic power is controlled at 140-180 W, and the ultrasonic frequency is 38-45 kHz; the concentration of the phosphoric acid solution is 5 wt%, and the aluminum alloy workpiece is immersed in the phosphoric acid solution for 15-20 min.

7. The method of claim 1, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. In S2, the polytetrafluoroethylene powder is ultrafine powder with a particle size of less than 5 μm, the electrostatic voltage is set to 75-92 kV during electrostatic powder spraying, the electrostatic current is set to 18-25 μA, the fluidization pressure is 0.05-0.10 MPa, and the powder spraying amount is 500-1200 g / min.

8. The method of claim 1, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. In S2, the temperature of the surface of the aluminum alloy workpiece after heating is 330-350℃.

9. The method of claim 1, wherein the aluminum alloy composite anodic oxide film is formed by anodizing an aluminum alloy substrate in an electrolyte containing phosphoric acid and a water-soluble organic acid. In S3, the surface grinding removal thickness of the composite film during magnetic rheological polishing and flattening of the magnetic rheological polishing liquid is controlled at 5-20 μm.

10. An aluminum alloy composite anodized film, characterized by, It is prepared by the method of any one of claims 1 to 9.

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