Method and device for multicolor micro-arc oxidation of alloy surface

Abstract

The invention belongs to the technical field of alloy material surface micro-arc oxidation, and particularly relates to a method and a device for alloy surface multi-color micro-arc oxidation. Aiming at the defects of non-uniform or discontinuous distribution and the like of a film layer formed by post-micro-arc oxidation during multi-color micro-arc oxidation in the prior art, the invention provides the method and the device for multi-color micro-arc oxidation of the alloy surface, and after constant-speed cooling, freeze drying, constant-speed heating, constant-temperature treatment and the like are carried out on the alloy, the multi-color micro-arc oxidation of the alloy surface is realized. The physical and chemical state of an alloy workpiece is effectively adjusted, and the uniformity of a film layer formed through post-micro-arc oxidation is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-arc oxidation of alloy material surfaces, and in particular relates to a method and a device for multi-color micro-arc oxidation of alloy surfaces. Background Art

[0002] Micro-arc oxidation (MAO) is a highly effective metal surface treatment technology that utilizes the instantaneous high temperature and high pressure generated by arc discharge to in-situ grow a ceramic film with excellent wear resistance, corrosion resistance, and insulation properties on valve metal surfaces. This technology is widely used in aviation, automotive, medical equipment, and electronics because it significantly improves the mechanical and chemical properties of material surfaces.

[0003] As market demands for product appearance and functionality continue to rise, multi-color micro-arc oxidation treatment of alloy surfaces not only enhances product aesthetics and meets consumer demand for personalization and aesthetics, but also allows for specific functional identification of products through different colored coatings. This is particularly important in the identification of electronic product exterior parts, precision crafts, and industrial equipment, where color can be used to distinguish different functional areas or indicate specific usage states.

[0004] Although micro-arc oxidation technology has achieved remarkable results in the formation of single-color films, there are still many challenges in achieving multi-color films. Current technologies can often only form single-color films on metal surfaces, which makes it difficult to meet the market demand for diversified designs and decorative features. In addition, in some methods, deionized water is used to clean the electrolyte on the surface of the alloy workpiece, and then the deionized water on the surface of the alloy workpiece is removed by high-temperature drying, resulting in defects such as microcracks or deformation inside and on the surface of the alloy workpiece, which in turn leads to defects such as uneven distribution or discontinuity in the film formed by subsequent micro-arc oxidation. In addition, some technologies require the use of expensive additives or special equipment, which not only increases production costs but also limits their application in industrial-scale production.

[0005] Therefore, the present invention proposes a micro-arc oxidation preparation method and system thereof that can achieve a color gradient effect, thereby improving the effect of the existing technology in color gradient control. Summary of the Invention

[0006] In view of the defects of uneven distribution or discontinuity in the film layer formed in the post-micro-arc oxidation during multi-color micro-arc oxidation in the existing technology, a method and device for multi-color micro-arc oxidation on the surface of an alloy are proposed. By subjecting the alloy to uniform cooling, freeze drying, uniform heating and constant temperature treatment, the physical and chemical state of the alloy is effectively adjusted, and the uniformity of the film layer formed in the post-micro-arc oxidation is improved.

[0007] In order to achieve the above purpose, the technical solutions adopted are: In a first aspect, the present invention provides a method for multi-color micro-arc oxidation of an alloy surface, comprising the following steps: S1. Workpiece pretreatment: degreasing, cleaning and activation of the alloy workpiece; S2. The alloy workpiece is placed in the electrolyte a, after micro-arc oxidation to form a first color film layer, the alloy workpiece is removed from the electrolyte a; S3. The electrolyte a is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly and treated at a constant temperature to remove deionized water from the surface of the alloy workpiece; S4. The alloy workpiece is placed in the electrolyte b, and after micro-arc oxidation, a second color film layer is formed, and the alloy workpiece is removed from the electrolyte b; S5. The electrolyte b is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly, and the deionized water is removed from the surface of the alloy workpiece after constant temperature treatment; S6. Repeat steps S2 to S5 to form a film layer of various colors on the surface of the alloy workpiece.

[0008] Furthermore, in step S3 and / or S5, the uniform cooling rate is 1-3°C / min.

[0009] Furthermore, in step S3 and / or S5, the freeze-drying temperature is 5-7° C., and the freeze-drying time is 30-360 min.

[0010] Furthermore, in step S3 and / or S5, the uniform heating rate is 1-3°C / min.

[0011] Furthermore, in step S3 and / or S5, the electrolyte on the surface of the alloy workpiece may be rinsed multiple times with deionized water and a cleaning agent.

[0012] Furthermore, in step S1, an organic solvent or an alkaline degreasing agent is used to soak and remove oil stains and impurities on the surface of the alloy workpiece, wherein the organic solvent includes one or more of acetone and gasoline, and the alkaline degreasing agent includes one or more of sodium hydroxide solution, sodium carbonate solution and sodium phosphate solution, and the soaking time is 5 to 15 minutes.

[0013] Furthermore, in step S1, deionized water and ultrasonic waves are used to remove tiny particles and residual impurities on the surface of the alloy workpiece. The ultrasonic treatment time is 3 to 10 minutes, and the ultrasonic frequency is 30 to 60 kHz.

[0014] Furthermore, in step S1, the surface of the alloy workpiece is activated using an acidic solution, wherein the acidic solution includes one or more of a dilute nitric acid solution, a hydrofluoric acid solution, a nitric acid solution and a sulfuric acid solution, and the activation treatment time is 1 to 5 minutes.

[0015] In the second aspect, the present invention also provides a device for multi-color micro-arc oxidation of alloy surfaces, comprising: a plurality of electrolytic cells, each electrolytic cell being filled with a different type of electrolyte; a plurality of power boxes, each power box being electrically connected to a plurality of electrolytic cells one by one; a circulating cooling box, the circulating cooling box being connected to the outer shell of each electrolytic cell through a water inlet pipe and a water outlet pipe, the circulating cooling box being used to maintain a constant temperature state of the electrolyte in each electrolytic cell; a cleaning box, the cleaning box being used to clean the electrolyte attached to the surface of the alloy workpiece; and a temperature regulating box, the temperature regulating box having the functions of uniform cooling, uniform heating and constant temperature treatment; the plurality of electrolytic cells, the plurality of power boxes, the circulating cooling box and the temperature regulating box are connected in sequence according to the industrial production order.

[0016] Furthermore, the device for multi-color micro-arc oxidation of metal surfaces also includes a robotic arm and a console, the robotic arm is used to stably clamp the alloy workpiece, and the console is used to control the operation of the device for multi-color micro-arc oxidation of metal surfaces.

[0017] The beneficial effects achieved by adopting the above technical solution are: ① In the present invention, after the alloy workpiece undergoes the first micro-arc oxidation, the uniform cooling treatment can effectively control the internal thermal stress of the alloy material, prevent the material from being deformed or cracked due to rapid temperature changes, and help maintain the structural integrity and microstructural stability of the alloy workpiece; ② Each time the micro-arc oxidation film is formed, thermal stress is introduced into the alloy workpiece. The present invention reduces the accumulation of thermal stress caused by drastic temperature changes by freeze-drying the alloy, which helps to maintain the original mechanical properties of the alloy workpiece and reduce microcracks or deformation caused by thermal stress; ③ In the present invention, after the freeze-drying of the alloy workpiece is completed, the freeze-dried alloy workpiece is uniformly heated to the working temperature by uniformly increasing the temperature, thereby avoiding local overheating of the alloy workpiece, thereby reducing the internal stress caused by temperature unevenness, further preventing defects such as microcracks and deformation in the alloy workpiece during the heating process, and providing a good working premise for the subsequent micro-arc oxidation of the alloy workpiece surface; ④ In the present invention, after the alloy workpiece is heated to the working temperature at a uniform speed, the alloy workpiece is subjected to constant temperature treatment, so that the alloy workpiece completely eliminates the changes in the physical and chemical properties of the material caused by temperature fluctuations, thereby ensuring the stability of the structural performance of the alloy workpiece; ⑤ This invention utilizes multiple independent electrolytic cells and precisely controlled micro-arc oxidation parameters to stably generate a multi-color film layer on the surface of the alloy workpiece. This effectively meets diverse design and decoration needs and significantly enhances the market added value of the product. ⑥ The design of multiple independent electrolytic cells and power supply boxes in this invention enables the device to independently control the micro-arc oxidation process for each color of electrolyte. This design greatly improves the accuracy and stability of color control, ensuring the consistency of quality and color of different color films. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention. The drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0019] Figure 1 The diagram is a schematic structural diagram of a device for multi-color micro-arc oxidation of alloy surfaces according to the present invention.

[0020] The meanings of the numbers in the figure are: 1. Electrolyzer, 101. First stirrer, 2. Power supply box; 3. Circulating cooling box, 301. Water inlet pipe, 302. Water outlet pipe, 303. Cooling box operating table; 4. Robotic arm, 5. Control console; 6. Liquid preparation barrel, 601. Slide rail, 602. Second agitator. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings of specific embodiments of the present invention to clearly and completely describe the exemplary embodiments of the present invention. Unless otherwise defined, technical or scientific terms used in the present invention should be given the common meanings understood by people with ordinary skills in the relevant field.

[0022] In a first aspect, the present invention provides a method for multi-color micro-arc oxidation of an alloy surface, comprising the following steps: S1. Workpiece pretreatment: degreasing, cleaning and activation of the alloy workpiece; S2. The alloy workpiece is placed in the electrolyte a, after micro-arc oxidation to form a first color film layer, the alloy workpiece is removed from the electrolyte a; S3. The electrolyte a is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly and treated at a constant temperature to remove deionized water from the surface of the alloy workpiece; S4. The alloy workpiece is placed in the electrolyte b, and after micro-arc oxidation, a second color film layer is formed, and the alloy workpiece is removed from the electrolyte b; S5. The electrolyte b is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly, and the deionized water is removed from the surface of the alloy workpiece after constant temperature treatment; S6. Repeat steps S2 to S5 to form a film layer of various colors on the surface of the alloy workpiece.

[0023] First, in the present invention, after the alloy workpiece undergoes the first micro-arc oxidation, the internal thermal stress of the alloy material can be effectively controlled by uniform cooling treatment, thereby preventing material deformation or cracking caused by rapid temperature changes, and helping to maintain the structural integrity and microstructural stability of the alloy workpiece.

[0024] Secondly, each time the micro-arc oxidation film is formed, thermal stress is introduced into the alloy workpiece. The present invention reduces the accumulation of thermal stress caused by drastic temperature changes by freeze-drying the alloy, which helps to maintain the original mechanical properties of the alloy workpiece and reduce microcracks or deformation caused by thermal stress.

[0025] Again, in the present invention, after the freeze-drying of the alloy workpiece is completed, the freeze-dried alloy workpiece is uniformly heated to the working temperature by uniformly increasing the temperature to avoid local overheating of the alloy workpiece, thereby reducing the internal stress caused by uneven temperature, and further preventing the alloy workpiece from having defects such as microcracks and deformation during the heating process, providing a good working premise for the subsequent micro-arc oxidation of the alloy workpiece surface.

[0026] Finally, in the present invention, after the alloy workpiece is heated to the working temperature at a uniform speed, the alloy workpiece is subjected to constant temperature treatment, so that the alloy workpiece completely eliminates the changes in the physical and chemical properties of the material caused by temperature fluctuations, ensuring the stability of the structural performance of the alloy workpiece.

[0027] It should be noted that, in the present invention, the alloy workpiece is a magnesium alloy workpiece, an aluminum alloy workpiece, a titanium alloy workpiece or other common alloy workpieces.

[0028] In some embodiments, in steps S3 and / or S5, the uniform cooling rate is 1-3°C / min. Excessively high uniform cooling rates may increase internal stress in the alloy workpiece, causing microcracks or other structural damage. Excessively low uniform cooling rates may result in low efficiency and increased production cycle time.

[0029] In some embodiments, in steps S3 and / or S5, the freeze-drying temperature is 5-7°C. When the freeze-drying temperature is too high, moisture may not be effectively sublimated, remaining on the surface or inside the alloy workpiece, affecting the uniformity and adhesion of the subsequent micro-arc oxidation film. When the freeze-drying temperature is too low, moisture may freeze too quickly on the surface or inside the alloy workpiece, increasing internal stress and inducing microcracks on the surface of the alloy workpiece.

[0030] In some embodiments, in steps S3 and / or S5, the freeze-drying time is 30 to 360 minutes. If the freeze-drying time is too short, moisture inside or on the surface of the alloy workpiece is not completely removed, affecting the effect of subsequent micro-arc oxidation. If the freeze-drying time is too long, production efficiency is reduced and energy is wasted.

[0031] In some embodiments, in steps S3 and / or S5, the uniform heating rate is 1-3°C / min. If the uniform heating rate is too high, the internal stress of the alloy workpiece will increase sharply, causing deformation or microcracks in the alloy workpiece. If the uniform heating rate is too low, the entire production process will be prolonged and efficiency will be reduced.

[0032] It should be noted that, in the present invention, the starting temperature of the uniform cooling and the ending temperature of the uniform heating of the alloy workpiece are both within the range of 20-35° C., and the actual temperature is the same as the working temperature of the electrolyte.

[0033] In some embodiments, in steps S3 and / or S5, the electrolyte on the surface of the alloy workpiece may be rinsed multiple times with deionized water and a cleaning agent to ensure that all residual electrolyte is completely removed to avoid affecting the subsequent micro-arc oxidation treatment.

[0034] In some embodiments, in step S1, an organic solvent or an alkaline degreaser is used to soak and remove oil stains and impurities on the surface of the alloy workpiece, wherein the organic solvent includes one or more of acetone and gasoline, and the alkaline degreaser includes one or more of sodium hydroxide solution, sodium carbonate solution, and sodium phosphate solution, and the soaking time is 5 to 15 minutes. By soaking the alloy workpiece in an organic solvent or an alkaline degreaser, grease, dust, and other impurities on the surface of the alloy workpiece are removed, thereby improving the adhesion and overall quality of the film layer. When the soaking time is too long, the surface of the alloy workpiece will be chemically damaged or excessively corroded, affecting its structural integrity; when the soaking time is too short, all grease and impurities cannot be fully removed, affecting the effect of subsequent processing steps and the quality of the coating.

[0035] In some embodiments, in step S1, deionized water and ultrasonic waves are used to remove tiny particles and residual impurities from the surface of the alloy workpiece, wherein the ultrasonic treatment time is 3 to 10 minutes and the ultrasonic frequency is 30 to 60 kHz. If the ultrasonic treatment time is too long or the ultrasonic frequency is too high, the surface of the alloy workpiece may be subjected to excessive mechanical vibration, thereby causing microscopic damage or changing the surface properties of the alloy workpiece. If the ultrasonic treatment time is too short or the ultrasonic frequency is too low, it is difficult to completely remove tiny impurity particles from the surface of the alloy workpiece, affecting the adhesion of subsequent film layers and the overall film quality.

[0036] In some embodiments, in step S1 , the surface of the alloy workpiece is activated using an acidic solution, wherein the acidic solution includes one or more of a dilute nitric acid solution, a hydrofluoric acid solution, a nitric acid solution, and a sulfuric acid solution.

[0037] It should be noted that protective equipment must be worn when operating reagents such as dilute nitric acid solution, hydrofluoric acid solution, nitric acid solution and sulfuric acid solution, and waste liquid must be handled according to environmental protection standards.

[0038] In this invention, activation treatment of the alloy workpiece surface enhances the chemical reactivity and surface roughness of the alloy, thereby strengthening the adhesion of the film during the subsequent micro-arc oxidation process. Simultaneously, by removing surface impurities and creating more active sites, the micro-arc oxidation film becomes more uniform and adherent, improving the film's mechanical and corrosion resistance.

[0039] In some embodiments, in step S1, the surface of the alloy workpiece is activated using an acidic solution for 1 to 5 minutes. If the activation time is too short, the surface of the alloy workpiece may not be completely cleaned or activated, thereby affecting the adhesion and uniformity of the subsequent micro-arc oxidation film. If the activation time is too long, the alloy workpiece may be excessively corroded, damaging the microstructure of the alloy workpiece and reducing its mechanical strength and durability.

[0040] It should be noted that after the surface of the alloy workpiece is activated with an acidic solution, the alloy workpiece needs to be rinsed with deionized water to remove the acidic solution on the surface of the alloy workpiece and avoid excessive corrosion of the surface of the alloy workpiece by the acidic solution.

[0041] In a second aspect, the present invention provides a device for multi-color micro-arc oxidation of metal surfaces, which is used to implement any of the above-mentioned methods for multi-color micro-arc oxidation of metal surfaces, and includes multiple electrolytic cells 1, multiple power boxes 2, a circulating cooling box 3, a cleaning box (not shown in the figure), and a temperature control box (not shown in the figure). Each electrolytic cell 1 is filled with a different type of electrolyte; each power box 2 is electrically connected to each of the multiple electrolytic cells 1 in a one-to-one correspondence; the circulating cooling box 3 is connected to the outer shell of each electrolytic cell 1 via a water inlet pipe 301 and a water outlet pipe 302, and is used to maintain a constant temperature state for the electrolyte in each electrolytic cell 1; the cleaning box is used to clean the electrolyte attached to the surface of the alloy workpiece; the temperature control box has the functions of uniform cooling, uniform heating, and constant temperature treatment; the multiple electrolytic cells 1, multiple power boxes 1, circulating cooling box 3, and temperature control box are connected in sequence according to industrial production order.

[0042] It should be noted that in the actual production process, each power box 2 must be grounded to reduce the risk of high-voltage discharge.

[0043] Furthermore, the temperature of the electrolyte in the electrolytic cell 1 is in the range of 20-35°C.

[0044] In some embodiments, the device for multi-color micro-arc oxidation of metal surfaces also includes a robotic arm 4 and a console 5, wherein the robotic arm 4 is used to stably grasp and clamp the alloy workpiece, and the console 5 is used to control the operation of the device for multi-color micro-arc oxidation of metal surfaces.

[0045] In the present invention, each time the alloy workpiece completes micro-arc oxidation in a certain electrolytic cell 1, it will be grabbed by the robotic arm 4 and placed in a cleaning box and a temperature regulating box in turn to clean the electrolyte and moisture on the surface of the alloy workpiece for subsequent micro-arc oxidation.

[0046] Specifically, the robotic arm 4 removes an alloy workpiece from an electrolytic cell 1 and places it in a cleaning tank. There, the workpiece undergoes deionized water spraying, ultrasonic vibration, and a cleaning agent circulation process to ensure that no electrolyte residue is left. The workpiece is then placed in a temperature-regulating chamber. In the temperature-regulating chamber, the workpiece undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Finally, the deionized water on the workpiece's surface is removed.

[0047] Furthermore, each electrolytic cell 1 is independent of each other, and each electrolytic cell 1 is made of corrosion-resistant and insulating materials, such as high-strength engineering plastics or metal materials that have been treated with anti-corrosion. Each electrolytic cell 1 is filled with electrolytes of different compositions, and each electrolyte is specifically used to produce micro-arc oxidation films of different colors. In addition, each electrolytic cell 1 is equipped with a temperature regulating device and a first agitator 101. The temperature regulating device can control the electrolyte temperature within the operating temperature range, which is 20~35°C, to ensure the stability of the micro-arc oxidation reaction. The first agitator 101 can evenly distribute the electrolyte components to avoid local concentration differences affecting the quality of the film layer.

[0048] In the present invention, each power supply box 2 is electrically connected to each electrolytic cell 1 in a one-to-one correspondence. In other words, each electrolytic cell 1 is controlled by an independent power supply box 2, thereby precisely controlling the micro-arc oxidation parameters within each cell 1, including voltage, current, and frequency. Furthermore, each power supply box 2 utilizes advanced digital control technology, enabling real-time parameter monitoring and adjustment to ensure the stability and accuracy of the micro-arc oxidation process. By pre-setting different parameter modes, the system can quickly adapt to the processing requirements of different electrolytes and colors.

[0049] In the present invention, a robotic arm 4 can precisely grasp alloy workpieces and move them to different electrolytic cells 1 for processing according to a set program. The robotic arm 4 has a motion accuracy of ±0.1mm and high-precision positioning and motion control capabilities, ensuring accurate grasping of alloy workpieces. The robotic arm 4 also has automatic identification and correction functions, ensuring accurate and efficient transfer of workpieces between electrolytic cells 1. Furthermore, the device of the present invention includes a fixture for holding the alloy workpiece. This fixture is designed according to the shape and size of the alloy workpiece, ensuring a secure grip without damaging the surface.

[0050] The present invention also includes a slide rail 601 and multiple liquid preparation barrels 6, each used to pre-prepare different types of electrolyte. The slide rail 601 is fixedly mounted directly above each electrolytic cell 1. A pipette gun connected to each liquid preparation barrel 6 via a connecting hose is slidably mounted on the slide rail 601. During actual production, each pipette gun slides on the slide rail 601 to directly above the corresponding electrolytic cell 1, thereby transferring the electrolyte in each liquid preparation barrel 6 to the corresponding electrolytic cell 1.

[0051] Furthermore, a second agitator 602 is installed at the bottom of the liquid preparation barrel 6. The second agitator 602 rotates continuously to drive the prefabricated electrolyte in the liquid preparation barrel 6 to rotate, thereby ensuring the uniformity and stability of the prefabricated electrolyte.

[0052] Table 1

[0053] Furthermore, the electrolyte and production process parameters used in the preparation of micro-arc oxidation films of different colors in the present invention are shown in Table 1. Table 1 discloses the electrolyte composition and dosage range used for micro-arc oxidation films of various colors such as black, gold, blue, red, green, white, yellow and orange, as well as the corresponding voltage, current, frequency and time ranges during the micro-arc oxidation treatment process.

[0054] The present invention is further described below with reference to the following examples.

[0055] Example 1. Two-color (white + black) micro-arc oxidation of magnesium alloy workpiece S1. Workpiece pretreatment: 1) Degreasing: Alkaline degreasing agent is prepared by mixing NaOH solution and Na2CO3 solution, wherein NaOH is 30g / L and Na2CO3 is 20g / L. The magnesium alloy workpiece is immersed in the alkaline degreasing agent for 10 minutes at a soaking temperature of 60°C. 2) Cleaning: Use deionized water combined with ultrasonic waves to clean the magnesium alloy workpiece in a cyclical manner. The ultrasonic treatment time is 5 minutes and the ultrasonic frequency is 40kHz. The cyclic cleaning is repeated 3 times, each time for 5 minutes. 3) Activation: Soak the magnesium alloy workpiece in a mixed solution of hydrofluoric acid (5% by volume) and nitric acid (15% by volume) for 1.5 minutes, and then rinse with deionized water.

[0056] S2. First Micro-arc Oxidation (white): Robotic arm 4 grasps the magnesium alloy workpiece and places it in the first electrolytic cell 1 for micro-arc oxidation, producing a white micro-arc oxidation film. The electrolyte in the first electrolytic cell 1 consists of 4g / L zinc sulfate solution, 3g / L boric acid solution, and 2g / L sodium sulfate solution. The micro-arc oxidation process is performed at a voltage of 240V, a current of 2.5A, a frequency of 750Hz, a treatment time of 7min, and a temperature of 25°C.

[0057] S3. Cleaning of magnesium alloy workpieces: 1) The magnesium alloy workpiece is removed from the first electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Use robotic arm 4 to remove the magnesium alloy workpiece from the cleaning chamber and place it in a temperature-regulating chamber. The workpiece undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Afterwards, the deionized water on the surface of the workpiece is removed. The uniform cooling rate is 1°C / min, the freeze drying temperature is 5°C, the freeze drying time is 60 minutes, the uniform heating rate is 1°C / min, and the constant temperature is 25°C.

[0058] S4. Second Micro-arc Oxidation (Black): After gripping the magnesium alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the second electrolytic cell 1 for micro-arc oxidation, producing a black micro-arc oxidation film. The electrolyte in the second electrolytic cell 1 consists of 8g / L manganese sulfate solution, 4g / L sodium hydroxide solution, and 3g / L sodium phosphate solution. The micro-arc oxidation process is performed at a voltage of 310V, a current of 5.5A, a frequency of 1050Hz, a treatment time of 11 minutes, and a temperature of 30°C.

[0059] S5. Cleaning of magnesium alloy workpieces: 1) The magnesium alloy workpiece is removed from the second electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Use robotic arm 4 to remove the magnesium alloy workpiece from the cleaning chamber and place it in a temperature-regulating chamber. The workpiece undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Afterwards, the deionized water on the surface of the workpiece is removed. The uniform cooling rate is 2°C / min, the freeze drying temperature is 6°C, the freeze drying time is 30 minutes, the uniform heating rate is 2°C / min, and the constant temperature treatment temperature is 30°C.

[0060] At this point, a white and black film has formed on the surface of the magnesium alloy workpiece. The color boundary is clearly defined, the film thickness is uniform (10μm for the white film and 15μm for the black film), and the surface hardness is ≥600HV. The boundary between the white and black films is straight and uniform, with no curved lines. The distribution of the white and black films is continuous and uniform, without any defects such as cracks or gaps.

[0061] Example 2. Three-color (blue + red + green) micro-arc oxidation of titanium alloy workpiece S1. Workpiece pretreatment: 1) Degreasing: Immerse the titanium alloy workpiece in an acetone organic solution and perform ultrasonic cleaning to remove oil stains on the surface of the titanium alloy workpiece. The immersion time is 5 minutes and the immersion temperature is 60°C. 2) Cleaning: Use deionized water combined with ultrasonic waves to clean the titanium alloy workpiece in a cyclical manner. The ultrasonic treatment time is 5 minutes and the ultrasonic frequency is 50kHz. The cyclic cleaning is repeated 3 times, each time for 5 minutes. 3) Activation: Soak the titanium alloy workpiece in a mixed solution of hydrofluoric acid (3% by volume) and sulfuric acid (10% by volume) for 2 minutes, and then rinse with deionized water.

[0062] S2. First Micro-arc Oxidation (Blue): Robotic arm 4 grasps the titanium alloy workpiece and places it in the first electrolytic cell 1 for micro-arc oxidation, producing a blue micro-arc oxidation film. The electrolyte in the first electrolytic cell 1 consists of 6g / L copper sulfate solution, 4g / L borax solution, and 3g / L potassium hydroxide solution. The micro-arc oxidation process is performed at a voltage of 280V, a current of 4.5A, a frequency of 900Hz, a treatment time of 10 minutes, and a temperature of 30°C.

[0063] S3. Titanium alloy workpiece cleaning: 1) The titanium alloy workpiece is removed from the first electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the titanium alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the workpiece's surface. The uniform cooling rate is 2°C / min, the freeze drying temperature is 6°C, the freeze drying time is 180 minutes, the uniform heating rate is 2°C / min, and the constant temperature is 30°C.

[0064] S4. Second Micro-arc Oxidation (Red): After gripping the titanium alloy workpiece with Robotic Arm 4, a portion of the workpiece is placed in the second electrolytic cell 1 for micro-arc oxidation, generating a red micro-arc oxidation film. The electrolyte in the second electrolytic cell 1 consists of 3g / L ferric sulfate solution, 4g / L sodium metaaluminate solution, and 2g / L EDTA-2Na solution. The micro-arc oxidation process is performed at a voltage of 260V, a current of 3.8A, a frequency of 890Hz, a treatment time of 11min, and a temperature of 35°C.

[0065] S5. Titanium alloy workpiece cleaning: 1) The titanium alloy workpiece is removed from the second electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the titanium alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the workpiece's surface. The uniform cooling rate is 2°C / min, the freeze drying temperature is 7°C, the freeze drying time is 180 minutes, the uniform heating rate is 2°C / min, and the constant temperature is 35°C.

[0066] S6. Third Micro-arc Oxidation (Green): After gripping the titanium alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the third electrolytic cell 1 for micro-arc oxidation, generating a green micro-arc oxidation film. The electrolyte in the third electrolytic cell 1 consists of 6g / L potassium dichromate solution, 4g / L sodium silicate solution, and 2.5g / L sodium fluoride solution. The micro-arc oxidation process is performed at a voltage of 290V, a current of 4.2A, a frequency of 890Hz, a treatment time of 9 minutes, and a temperature of 25°C.

[0067] S7. Titanium alloy workpiece cleaning: 1) The titanium alloy workpiece is removed from the third electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Use robotic arm 4 to remove the titanium alloy workpiece from the cleaning chamber and place it in a temperature-regulating chamber. After undergoing a series of processes, such as uniform cooling, freeze drying, uniform heating, and constant temperature treatment, the deionized water on the surface of the workpiece is removed. The uniform cooling rate is 1°C / min, the freeze drying temperature is 5°C, the freeze drying time is 180 minutes, the uniform heating rate is 1°C / min, and the constant temperature is 25°C.

[0068] At this point, a blue, red, and green film has formed on the titanium alloy workpiece's surface. The color boundaries are clearly defined and the film thickness is uniform (12μm for the blue film, 15μm for the red film, and 18μm for the green film). The film withstands salt spray testing for over 500 hours, achieving a color fastness rating of Class 4. The boundaries between the blue, red, and green films are straight and uniform, with no curved lines. The distribution of the blue, red, and green films is continuous and uniform, with no defects such as cracks or gaps.

[0069] Example 3. Four-color (white + yellow + brown + black) micro-arc oxidation of aluminum alloy workpiece S1. Workpiece pretreatment: 1) Degreasing: Alkaline degreasing agent is prepared by mixing NaOH solution and Na2CO3 solution, wherein NaOH is 30g / L and Na2CO3 is 20g / L. The magnesium alloy workpiece is immersed in the alkaline degreasing agent for 10 minutes at a soaking temperature of 60°C. 2) Cleaning: Use deionized water combined with ultrasonic waves to clean the aluminum alloy workpiece in a cyclical manner. The ultrasonic treatment time is 3 minutes and the ultrasonic frequency is 60kHz. The cyclic cleaning is repeated 3 times, each time for 3 minutes. 3) Activation: Soak the aluminum alloy workpiece in nitric acid solution (10% by volume) for 2 minutes, and then rinse with deionized water.

[0070] S2. First Micro-arc Oxidation (white): Robotic arm 4 grasps the aluminum alloy workpiece and places it in the first electrolytic cell 1 for micro-arc oxidation, producing a white micro-arc oxidation film. The electrolyte in the first electrolytic cell 1 consists of 4g / L zinc sulfate solution, 3g / L boric acid solution, and 2g / L sodium sulfate solution. The micro-arc oxidation process is performed at a voltage of 240V, a current of 2.5A, a frequency of 750Hz, a treatment time of 7min, and a temperature of 20°C.

[0071] S3. Cleaning of aluminum alloy workpieces: 1) The aluminum alloy workpiece is removed from the first electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the aluminum alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the surface of the alloy workpiece. The uniform cooling rate is 2°C / min, the freeze drying temperature is 7°C, the freeze drying time is 360 minutes, the uniform heating rate is 2°C / min, and the constant temperature is 20°C.

[0072] S4. Second Micro-arc Oxidation (Yellow): After gripping the aluminum alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the second electrolytic cell 1 for micro-arc oxidation, producing a yellow micro-arc oxidation film. The electrolyte in the second electrolytic cell 1 consists of 4g / L sodium molybdate solution, 3g / L disodium hydrogen phosphate solution, and 2g / L potassium sodium tartrate solution. The micro-arc oxidation process is performed at a voltage of 270V, a current of 3.5A, a frequency of 850Hz, a treatment time of 9 minutes, and a temperature of 30°C.

[0073] S5. Cleaning of aluminum alloy workpieces: 1) The aluminum alloy workpiece is removed from the second electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the aluminum alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the surface of the alloy workpiece. The uniform cooling rate is 1°C / min, the freeze drying temperature is 5°C, the freeze drying time is 180 minutes, the uniform heating rate is 1°C / min, and the constant temperature is 30°C.

[0074] S6. Third Micro-arc Oxidation (Brown): After gripping the aluminum alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the third electrolytic cell 1 for micro-arc oxidation, forming a brown micro-arc oxidation film. The electrolyte in the third electrolytic cell 1 consists of 5g / L ferric sulfate solution, 3g / L sodium metaaluminate solution, and 2g / L EDTA-2Na solution. The micro-arc oxidation process is performed at a voltage of 260V, a current of 3.5A, a frequency of 850Hz, a treatment time of 10min, and a temperature of 20°C.

[0075] S7. Cleaning of aluminum alloy workpieces: 1) The aluminum alloy workpiece is removed from the third electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the aluminum alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the surface of the alloy workpiece. The uniform cooling rate is 1.5°C / min, the freeze drying temperature is 6°C, the freeze drying time is 60 minutes, the uniform heating rate is 1.5°C / min, and the constant temperature is 20°C.

[0076] S8. Fourth Micro-arc Oxidation (Black): After gripping the aluminum alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the fourth electrolytic cell 1 for micro-arc oxidation, producing a black micro-arc oxidation film. The electrolyte in the fourth electrolytic cell 1 consists of 8g / L manganese sulfate solution, 4g / L sodium hydroxide solution, and 3g / L sodium phosphate solution. The micro-arc oxidation process is performed at a voltage of 310V, a current of 5.5A, a frequency of 1050Hz, a treatment time of 11 minutes, and a temperature of 25°C.

[0077] S9. Cleaning of aluminum alloy workpieces: 1) The aluminum alloy workpiece is removed from the third electrolytic cell 1 by a robotic arm 4 and placed in a cleaning tank. The workpiece is then cleaned by spraying with deionized water, ultrasonic waves, and a cleaning agent cycle until no electrolyte remains. 2) Robotic arm 4 removes the aluminum alloy workpiece from the cleaning chamber and places it in a temperature-regulating chamber, where it undergoes a series of processes: uniform cooling, freeze drying, uniform heating, and constant temperature treatment. Deionized water is then removed from the surface of the alloy workpiece. The uniform cooling rate is 2.5°C / min, the freeze drying temperature is 5°C, the freeze drying time is 240 minutes, the uniform heating rate is 2.5°C / min, and the constant temperature treatment temperature is 25°C.

[0078] At this point, four layers of film—white, yellow, brown, and black—are formed on the aluminum alloy workpiece. The color boundaries are clearly defined and the film thickness is uniform (12μm for the white film, 14μm for the yellow film, 16μm for the brown film, and 18μm for the black film). The boundaries between the white, yellow, brown, and black layers are straight and uniform, with no curved lines. The distribution of the white, yellow, brown, and black layers is continuous and uniform, with no defects such as cracks or gaps.

[0079] Comparison 1. Two-color (white + black) micro-arc oxidation of magnesium alloy workpiece S1. Workpiece pretreatment: 1) Degreasing: Alkaline degreasing agent is prepared by mixing NaOH solution and Na2CO3 solution, wherein NaOH is 30g / L and Na2CO3 is 20g / L. The magnesium alloy workpiece is immersed in the alkaline degreasing agent for 10 minutes at a soaking temperature of 60°C. 2) Cleaning: Use deionized water combined with ultrasonic waves to clean the magnesium alloy workpiece in a cyclical manner. The ultrasonic treatment time is 5 minutes and the ultrasonic frequency is 40kHz. The cyclic cleaning is repeated 3 times, each time for 5 minutes. 3) Activation: Soak the magnesium alloy workpiece in a mixed solution of hydrofluoric acid (5% by volume) and nitric acid (15% by volume) for 1.5 minutes, and then rinse with deionized water.

[0080] S2. First Micro-arc Oxidation (white): Robotic arm 4 grasps the magnesium alloy workpiece and places it in the first electrolytic cell 1 for micro-arc oxidation, producing a white micro-arc oxidation film. The electrolyte in the first electrolytic cell 1 consists of 4g / L zinc sulfate solution, 3g / L boric acid solution, and 2g / L sodium sulfate solution. The micro-arc oxidation process is performed at a voltage of 240V, a current of 2.5A, a frequency of 750Hz, a treatment time of 7min, and a temperature of 25°C.

[0081] S3. Cleaning of magnesium alloy workpieces: The magnesium alloy workpiece is removed from the first electrolytic cell 1 by a robotic arm 4 and subjected to conventional deionized water washing and high-temperature drying at a temperature of 105° C. for 120 minutes.

[0082] S4. Second Micro-arc Oxidation (Black): After gripping the magnesium alloy workpiece with robotic arm 4, a portion of the workpiece is placed in the second electrolytic cell 1 for micro-arc oxidation, producing a black micro-arc oxidation film. The electrolyte in the second electrolytic cell 1 consists of 8g / L manganese sulfate solution, 4g / L sodium hydroxide solution, and 3g / L sodium phosphate solution. The micro-arc oxidation process is performed at a voltage of 310V, a current of 5.5A, a frequency of 1050Hz, a treatment time of 11 minutes, and a temperature of 30°C.

[0083] S5. Cleaning of magnesium alloy workpieces: The magnesium alloy workpiece is removed from the second electrolytic cell 1 by a robotic arm 4 and subjected to conventional deionized water washing and high-temperature drying at a temperature of 105° C. for 120 minutes.

[0084] At this point, a white and black film has formed on the surface of the magnesium alloy workpiece. The boundary between the white and black layers is not straight, but rather has a distinct curve. Furthermore, both layers have defects such as bumps and gaps, resulting in poor aesthetics.

[0085] In Examples 1-3, the surface cleaning electrolyte and deionized water for the alloy workpieces were subjected to uniform cooling, freeze drying, uniform heating, and constant temperature treatment. In contrast, the surface cleaning electrolyte for the alloy workpieces in Comparative Example 1 was conventionally cleaned with deionized water and then dried at high temperature. Compared to Comparative Example 1, the various colored films on the alloy workpieces in Examples 1-3 were more uniform, free of defects such as cracks or gaps, and exhibited straight, uniform boundaries between each color. This is because the uniform cooling, freeze drying, and uniform heating and constant temperature treatments reduced the accumulation of thermal stress in the alloy workpieces caused by drastic temperature changes, avoided the formation of defects such as microcracks and protruding deformations in the alloy workpieces, and thus ensured the uniformity of the micro-arc oxidation film on the alloy surface.

[0086] It should be understood that in Specific Examples 1 to 3 and Comparative Example 1, the first electrolytic cell 1, the second electrolytic cell 1, the third electrolytic cell 1, and the fourth electrolytic cell 1 are merely for ease of description in each embodiment. That is, in different embodiments, the first (second / third / fourth) electrolytic cell 1 is not the same electrolytic cell 1.

[0087] It should be noted that when one element is expressed as “connected”, “coupled” or “connected” to another element, it may mean that they are directly connected, coupled or connected, but it should be understood that there may be intermediate elements between the two; that is, the positional relationship of direct connection and indirect connection is covered.

[0088] It should be noted that the use of "a" or "an" and similar words does not necessarily indicate a limitation of quantity. "Include" or "comprising" and similar words mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0089] It should be noted that terms such as "up", "down", "left" and "right" that indicate orientation or positional relationships are only used to indicate relative positional relationships. This is for the convenience of describing the present invention, and does not mean that the device or element must have a specific orientation, be constructed and operated in a specific orientation. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0090] While preferred embodiments for implementing the present invention have been described in detail above, it should be understood that these embodiments are provided for illustrative purposes only and are not intended to limit the scope, applicability, or configuration of the present invention in any way. The scope of the present invention is defined by the appended claims and their equivalents. Persons skilled in the art may make numerous modifications to the aforementioned embodiments in light of the present invention, and such modifications are intended to fall within the scope of the present invention.

Claims

1. A method for multicolor micro-arc oxidation of alloy surface, characterized in that: The following steps are involved: S1. Workpiece pretreatment: degreasing, cleaning and activation of the alloy workpiece; S2. placing the alloy workpiece in electrolyte a, forming a first color film layer after micro-arc oxidation, and removing the alloy workpiece from electrolyte a; S3. The electrolyte a is washed with deionized water on the surface of the alloy workpiece, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly and treated at a constant temperature to remove the deionized water on the surface of the alloy workpiece; S4. The alloy workpiece is placed in electrolyte b, and a second color film layer is formed after micro-arc oxidation, and the alloy workpiece is removed from electrolyte b; S5. The electrolyte b is cleaned on the surface of the alloy workpiece with deionized water, and then the alloy workpiece is cooled uniformly, freeze-dried, heated uniformly, and the deionized water is removed from the surface of the alloy workpiece after constant temperature treatment; S6. Circulate steps S2 to S5 to form a film layer of various colors on the surface of the alloy workpiece.

2. A method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S3 and / or S5, the uniform cooling rate is 1-3°C / min.

3. A method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S3 and / or S5, the freeze-drying temperature is 5-7° C., and the freeze-drying time is 30-360 min.

4. The method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S3 and / or S5, the uniform heating rate is 1-3°C / min.

5. The method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S3 and / or S5, deionized water and a cleaning agent may be used to rinse the electrolyte on the surface of the alloy workpiece multiple times.

6. A method for multi-color micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, an organic solvent or an alkaline degreasing agent is used to soak and remove oil stains and impurities on the surface of the alloy workpiece, wherein the organic solvent comprises one or more of acetone and gasoline, and the alkaline degreasing agent comprises one or more of sodium hydroxide solution, sodium carbonate solution and sodium phosphate solution, and the soaking time is 5 to 15 minutes.

7. A method for multi-color micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, deionized water and ultrasonic waves are used to remove tiny particles and residual impurities on the surface of the alloy workpiece. The ultrasonic treatment time is 3 to 10 minutes, and the ultrasonic frequency is 30 to 60 kHz.

8. The method for multicolor micro-arc oxidation of alloy surface according to claim 1, characterized in that: In step S1, an acidic solution is used to activate the surface of the alloy workpiece. The acidic solution includes one or more of a dilute nitric acid solution, a hydrofluoric acid solution, a nitric acid solution and a sulfuric acid solution. The activation treatment time is 1 to 5 minutes.

9. A device for multicolor micro-arc oxidation of alloy surface, used to implement the method for multicolor micro-arc oxidation of alloy surface as claimed in any one of claims 1 to 8, characterized in that: include: A plurality of electrolytic cells, each containing a different type of electrolyte; A plurality of power supply boxes, each power supply box being electrically connected to a plurality of electrolytic cells in a one-to-one correspondence; A circulating cooling box, the circulating cooling box is connected to the shell of each electrolytic cell through a water inlet pipe and a water outlet pipe, and the circulating cooling box is used to maintain a constant temperature state of the electrolyte in each electrolytic cell; A cleaning box, the cleaning box is used to clean the electrolyte attached to the surface of the alloy workpiece; and a temperature regulating box, which has the functions of uniform temperature reduction, uniform temperature increase and constant temperature treatment; The multiple electrolytic cells, multiple power boxes, circulating cooling boxes and temperature regulating boxes are connected in sequence according to industrial production sequence.

10. The device for multi-color micro-arc oxidation of alloy surface according to claim 9, characterized in that: The device for multi-color micro-arc oxidation of alloy surface also includes a mechanical arm and a control console, wherein the mechanical arm is used for stably clamping the alloy workpiece, and the control console is used for controlling the operation of the device for multi-color micro-arc oxidation of alloy surface.

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