7-series aluminum alloy micro-arc oxidation surface treatment method

Abstract

The invention belongs to the technical field of metal material surface treatment, and particularly relates to a 7-series aluminum alloy micro-arc oxidation surface treatment method which sequentially comprises the following steps of surface pretreatment, electrolyte preparation, micro-arc oxidation operation and post-treatment. According to the surface treatment method, the 7-series aluminum alloy surface pretreatment link is optimized, and the adverse effect of the workpiece surface state difference on micro-arc oxidation is effectively avoided; ultrasonic-assisted treatment and magnetic field-assisted treatment are introduced, so that the uniformity of the film layer is improved; the film thickness control method is optimized, and the film thickness uniformity is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material surface treatment, and in particular relates to a micro-arc oxidation surface treatment method for 7 series aluminum alloys. Background Art

[0002] 7-series aluminum alloys are aluminum alloys with zinc as the primary alloying element. Due to their excellent mechanical properties, they are often used in the manufacture of aircraft skins, wings, and other components, as well as in automotive body panels and wheels. Furthermore, 7-series aluminum alloys are often used in the manufacture of housings for electronic products in the 3C (computer, communications, and consumer electronics) sector due to their superior surface smoothness, high gloss, excellent corrosion resistance, high hardness, and wear resistance (these characteristics, corresponding to mechanical properties, can be simply summarized as "surface properties"). The high surface hardness and good heat dissipation of 7-series aluminum alloys can protect the internal components of 3C products and enhance the overall performance of the equipment. After surface treatment, they can exhibit a variety of colors and glosses to meet consumers' diverse demands for appearance.

[0003] 3C products place stringent demands on the appearance and functionality of aluminum alloy surfaces. While traditional anodizing improves corrosion resistance and hardness, the 3C market requires more sophisticated surface treatment technologies to achieve high gloss, unique textures, and a superior tactile feel. Micro-arc oxidation, a surface treatment technique that in-situ grows a ceramic film on the metal surface, is widely used in the surface treatment of aluminum alloys and other metal materials, and is particularly effective in improving the surface properties of 7-series aluminum alloys used in 3C products.

[0004] Achieving uniform film thickness is a key technical challenge in the micro-arc oxidation process. When processing complex aluminum alloy components for consumer electronics, the uneven electric field distribution leads to inconsistent film growth rates in different locations during the micro-arc oxidation process, resulting in uneven film thickness and performance. For example, the film may be thinner in corners and grooves of mobile phone frames, directly affecting overall surface properties. Summary of the Invention

[0005] In response to the problems in the prior art, the present invention proposes a micro-arc oxidation surface treatment method for 7 series aluminum alloys to improve the "surface performance" of 7 series aluminum alloys and meet the technical requirements of the 3C field. The technical solution of the present invention is as follows:

[0006] The micro-arc oxidation surface treatment method of 7 series aluminum alloy comprises the following steps in sequence:

[0007] Step 1: Surface pretreatment, first mechanical surface treatment, then chemical pretreatment, as follows:

[0008] a. First, perform surface mechanical treatment: Perform fine mechanical treatment on the 7 series aluminum alloy workpiece, such as grinding and polishing, to reduce the surface roughness and eliminate the defects and unevenness of the original surface; use sandpaper of different grit sizes to polish gradually, and finally polish with polishing paste with a grit size of 0.5-1μm to make the surface roughness reach Ra0.1-0.3μm, providing a uniform reaction basis for micro-arc oxidation;

[0009] b. Chemical pretreatment: first perform alkaline washing to remove oil stains and natural oxide film, then perform acid washing to remove alkaline washing residues and activate the surface; during alkaline washing, use 50-80g / L sodium hydroxide solution, control the temperature at 50-70°C, and treat for 3-5 minutes; acid washing uses 5%-10% nitric acid solution, and treat at room temperature for 1-2 minutes to ensure uniform surface condition and promote uniform micro-arc oxidation reaction;

[0010] Step 2: Electrolyte preparation: Select an appropriate electrolyte formula based on the treatment purpose and the characteristics of the aluminum alloy. The electrolyte contains a main salt, a buffer, and additives. Use a phosphate electrolyte with a potassium dihydrogen phosphate content of 5-10 g / L, a boric acid content of 3-5 g / L, and an EDTA chelating agent content of 0.5-1.5 g / L. Accurately weigh each component in proportion, add deionized water, and stir to dissolve to ensure that the electrolyte is uniform and free of precipitation.

[0011] Step 3: Micro-arc oxidation operation, including the following steps:

[0012] a. Clamp the workpiece and inject the electrolyte: clamp the pretreated workpiece firmly with a fixture and place it in the micro-arc oxidation reaction tank, ensuring that the workpiece is completely immersed in the electrolyte and does not contact the tank wall and other components. Slowly inject the prepared electrolyte into the reaction tank through a pipe or funnel to reach the specified liquid level, which should generally be 5 to 10 cm higher than the top of the workpiece;

[0013] b. Set process parameters and start the equipment: Set process parameters according to the aluminum alloy material, workpiece shape and film layer requirements, set the initial voltage to 200-250V, and the current density to 5-8A / dm 2 , pulse frequency 500 ~ 1000Hz, duty cycle 20% ~ 40%, processing time 20 ~ 30 minutes, after the parameter setting is completed, start the micro-arc oxidation equipment, the power supply output current and voltage, so that the workpiece surface in the electrolyte undergoes micro-arc oxidation reaction, and micro-arc discharge is observed on the workpiece surface, accompanied by sparks and bubbles;

[0014] c. Process monitoring and adjustment: During the micro-arc oxidation process, the equipment operating status and process parameter changes are continuously monitored. The voltage and current fluctuations are observed through the equipment's built-in monitoring system, and the data is recorded every 5 to 10 minutes. At the same time, the electrolyte temperature changes are observed and the temperature is controlled at 20 to 40°C through the cooling system to prevent excessive temperature from affecting the film quality.

[0015] Step 4: Post-processing, specifically including the following steps:

[0016] a. Workpiece cleaning: After the micro-arc oxidation treatment is completed, turn off the power of the equipment, remove the workpiece from the electrolyte, and immediately rinse it in running water to remove the residual electrolyte on the surface. The rinsing time is 3 to 5 minutes to ensure that there is no electrolyte residue on the surface to prevent the residual electrolyte from corroding the film layer or affecting the subsequent performance;

[0017] b. Post-treatment of the membrane layer: Use hot water sealing method to soak the cleaned workpiece in deionized water at 95-100°C for 20-30 minutes; organic coating can also be used, such as spraying epoxy resin paint to improve the protective performance and decorative properties of the membrane layer; after coating, cure at 150-180°C for 1-2 hours.

[0018] As an improvement to the above technical solution, in the micro-arc oxidation operation in step 3, auxiliary treatment means are also used, including ultrasonic assisted treatment and / or magnetic field assisted treatment. The specific method is as follows:

[0019] Ultrasonic-assisted treatment: set the ultrasonic frequency to 20-40kHz and the power to 100-300W;

[0020] Magnetic field assisted treatment: A magnetic field is set around the micro-arc oxidation device, and the magnetic field strength is controlled at 0.1~0.5T. The ions perform spiral motion under the action of the magnetic field, which increases the uniformity on the workpiece surface and uniformly grows the film layer.

[0021] As an improvement to the above technical solution, in the micro-arc oxidation operation phase of step three, the control is carried out in steps. The specific method is as follows:

[0022] Stage 1: Uniform arc nucleation: The pre-treated workpiece is clamped vertically and firmly between the electrodes, ensuring that the electrode spacing is 20 mm, the initial voltage is set to 220 V, and the current density is (6 ± 1) A / dm 2 , pulse frequency 500Hz, duty cycle 25%. This stage forms uniform crystal nuclei, providing a uniform foundation for subsequent film growth;

[0023] Stage 2: Stable growth: Slowly increase the voltage to 300 V and adjust the current density to (10±1) A / dm 2 , the pulse frequency was increased to 800Hz, the duty cycle was maintained at 30%, the micro-arc discharge phenomenon was closely observed to ensure uniform discharge, and the voltage and current data were recorded every 5 minutes. If the parameter fluctuation exceeded ±5%, the parameters were fine-tuned in time to maintain uniform film growth;

[0024] Phase III: Slow Thickening and Optimization: Fine-tune the voltage to 320V and maintain the current density at (10±1)A / dm2 , the pulse frequency is maintained at 800 Hz, and the duty cycle is adjusted to 35%; at the same time, the cooling system and stirring device are turned on to control the electrolyte temperature at 25-30°C to ensure uniform electrolyte temperature and composition, and prevent local overheating from causing rapid film growth or defects.

[0025] The micro-arc oxidation surface treatment method for 7 series aluminum alloys described in the present invention effectively improves the "surface properties" of 7 series aluminum alloys and meets the technical requirements of the 3C field. Its beneficial effects are:

[0026] 1. The surface treatment method described in this invention optimizes the surface pretreatment process for 7-series aluminum alloys, employing fine mechanical treatment followed by chemical pretreatment. Mechanical treatment involves sanding with sandpaper of varying grits and polishing with a polishing paste of a specific grit size to reduce surface roughness and provide a uniform reaction foundation for subsequent micro-arc oxidation. Chemical pretreatment involves alkaline and acid washing to remove oil stains, oxide films, and alkaline wash residues, activate the workpiece surface, and promote a uniform micro-arc oxidation reaction. This pretreatment effectively mitigates the adverse effects of workpiece surface condition variations on micro-arc oxidation.

[0027] 2. The surface treatment method described in this invention incorporates ultrasonic and magnetic field-assisted treatments. The ultrasonic cavitation effect enhances mass and heat transfer in the electrolyte, causing tiny bubbles to burst on the workpiece surface, promoting full contact between the electrolyte and the workpiece, and improving film uniformity, particularly for workpieces with complex shapes. Magnetic field-assisted treatment alters the ion motion trajectory in the electrolyte, resulting in a more uniform ion distribution and, in turn, promoting uniform film growth. These auxiliary methods optimize the micro-arc oxidation process at a physical level and have a positive impact on improving film quality.

[0028] 3. The surface treatment method described in the present invention optimizes the film thickness control method. The film thickness is precisely controlled in stages during the micro-arc oxidation operation. In the uniform arc initiation and nucleation stage, specific process parameters are used to uniformly initiate the micro-arc oxidation reaction and form uniform crystal nuclei. In the stable growth stage, parameters are rationally adjusted based on the film thickening, and micro-arc discharge phenomena are closely monitored to ensure continuous and stable film growth. In the slow thickening and optimization stage, parameters are fine-tuned to slowly thicken the film. Simultaneously, the cooling system and stirring device are activated to uniformly control the electrolyte temperature and composition, reduce internal stress in the film, and optimize the film structure. This staged and precise film thickness control method effectively improves film thickness uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the micro-arc oxidation surface treatment method for 7 series aluminum alloys described in the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0031] like Figure 1 The micro-arc oxidation surface treatment method for 7 series aluminum alloys of the present invention comprises the following steps in sequence:

[0032] Step 1: Surface pretreatment, first mechanical surface treatment, then chemical pretreatment, as follows:

[0033] a. First, perform surface mechanical treatment: Perform fine mechanical treatment on the 7 series aluminum alloy workpiece, such as grinding and polishing, to reduce the surface roughness and eliminate the defects and unevenness of the original surface. During grinding, use sandpaper of different grits to grind gradually, and finally polish with polishing paste with a grit size of 0.5-1μm to achieve a surface roughness of Ra0.1-0.3μm, providing a uniform reaction foundation for micro-arc oxidation.

[0034] b. Chemical pretreatment: Chemical pretreatment further cleans and activates the workpiece surface. Alkaline cleaning removes oil and the natural oxide film, followed by pickling to remove residue and activate the surface. For the alkaline wash, use a 50-80g / L sodium hydroxide solution at a temperature of 50-70°C for 3-5 minutes. For the pickling, use a 5%-10% nitric acid solution at room temperature for 1-2 minutes to ensure a uniform surface condition and promote a uniform micro-arc oxidation reaction.

[0035] Step 2: Electrolyte Preparation: Select an appropriate electrolyte formula based on the treatment purpose and the characteristics of the aluminum alloy. The electrolyte contains a primary salt (such as phosphate, silicate, etc.), a buffer (such as boric acid), and additives (such as chelating agents, surfactants). For example, in a phosphate electrolyte, the content of potassium dihydrogen phosphate is 5-10g / L, the content of boric acid is 3-5g / L, and the content of EDTA chelating agent is 0.5-1.5g / L. After accurately weighing each component according to the proportion, add deionized water and stir to dissolve, ensuring that the electrolyte is uniform and free of precipitation.

[0036] Step 3: Micro-arc oxidation operation, including the following steps:

[0037] a. Clamp the workpiece and inject the electrolyte: Securely clamp the pretreated workpiece with a fixture and place it in the micro-arc oxidation reaction tank, ensuring that the workpiece is completely immersed in the electrolyte and does not come into contact with the tank walls or other components. Slowly inject the prepared electrolyte into the reaction tank through a pipe or funnel to reach the specified liquid level, which should generally be 5 to 10 cm above the top of the workpiece.

[0038] b. Set process parameters and start the equipment: Set process parameters such as voltage, current density, processing time, pulse frequency and duty cycle according to the aluminum alloy material, workpiece shape and film layer requirements. For example, when processing 7 series aluminum alloy, the initial voltage is set to 200-250V and the current density is 5-8A / dm 2, pulse frequency 500-1000Hz, duty cycle 20%-40%, processing time 20-30 minutes. After the parameters are set, the micro-arc oxidation equipment is started, and the power supply outputs current and voltage to cause micro-arc oxidation reaction on the surface of the workpiece in the electrolyte. Micro-arc discharge is observed on the workpiece surface, accompanied by sparks and bubbles.

[0039] c. Process Monitoring and Adjustment: During the micro-arc oxidation process, continuously monitor the equipment's operating status and process parameter changes. Observe voltage and current fluctuations through the equipment's built-in monitoring system, recording data every 5-10 minutes. If abnormal parameter fluctuations are detected, such as a sudden increase in voltage or unstable current, promptly inspect the equipment and electrolyte. Adjust parameters or suspend processing if necessary for troubleshooting. Also, monitor electrolyte temperature changes and maintain the temperature between 20-40°C using the cooling system to prevent excessive temperatures from affecting film quality.

[0040] Step 4: Post-processing, specifically including the following steps:

[0041] a. Workpiece Cleaning: After the micro-arc oxidation treatment is completed, turn off the power supply of the equipment, remove the workpiece from the electrolyte, and immediately rinse it in running water to remove any residual electrolyte on the surface. The rinsing time is generally 3 to 5 minutes to ensure that there is no electrolyte residue on the surface to prevent residual electrolyte from corroding the film layer or affecting subsequent performance.

[0042] b. Film Post-treatment: Sealing is often performed to improve the film's corrosion resistance and seal its pores. This can be done by soaking the cleaned workpiece in deionized water at 95-100°C for 20-30 minutes. Alternatively, an organic coating, such as spray epoxy paint, can be used to enhance the film's protective and decorative properties. After coating, the workpiece is cured at 150-180°C for 1-2 hours.

[0043] The micro-arc oxidation surface treatment method for 7 series aluminum alloys of the present invention further employs auxiliary treatment means during the micro-arc oxidation operation in step 3, including ultrasonic-assisted treatment and / or magnetic-field-assisted treatment. The specific method is as follows:

[0044] Ultrasonic-assisted treatment: Introducing ultrasound into the micro-arc oxidation process, its cavitation effect enhances mass and heat transfer in the electrolyte. Ultrasonic bubbles burst on the workpiece surface, promoting full contact between the electrolyte and the workpiece, resulting in a more uniform reaction. Setting the ultrasonic frequency to 20-40 kHz and the power to 100-300 W effectively improves film uniformity, especially for complex workpieces.

[0045] Magnetic field-assisted treatment: Applying an external magnetic field can change the trajectory of ions in the electrolyte, making their distribution more uniform. A magnetic field is set around the micro-arc oxidation device, and the magnetic field strength is controlled at 0.1-0.5T. The ions perform spiral motion under the action of the magnetic field, increasing the uniformity of the workpiece surface, thereby promoting uniform film growth.

[0046] In the micro-arc oxidation surface treatment method for 7 series aluminum alloys of the present invention, in the micro-arc oxidation operation stage of step 3, fine control is performed in steps to form a uniform film thickness. The specific method is as follows:

[0047] Phase 1: Uniform arc nucleation (0-5 minutes): The pre-treated workpiece is clamped vertically and firmly between the electrodes, ensuring that the electrode spacing is 20 mm. The initial voltage is set to 220 V and the current density is (6 ± 1) A / dm 2 , pulse frequency 500Hz, duty cycle 25%. In this stage, relatively low and stable parameters are used to start the micro-arc oxidation reaction evenly on the workpiece surface, forming uniform crystal nuclei and providing a uniform foundation for subsequent film growth.

[0048] Stage 2: Stable growth (5-15 minutes): After 5 minutes, slowly increase the voltage to 300 V and adjust the current density to (10±1) A / dm 2 , the pulse frequency was increased to 800Hz, and the duty cycle was maintained at 30%. As the film gradually thickened, the parameters were appropriately increased to ensure continued stable film growth. During this stage, the micro-arcing phenomenon was closely observed to ensure uniform discharge. The voltage and current data were recorded every 5 minutes. If the parameter fluctuation exceeded ±5%, the parameters were fine-tuned in a timely manner to maintain uniform film growth.

[0049] Stage 3: Slow thickening and optimization (15-25 minutes): After 15 minutes, adjust the voltage to 320V and maintain the current density at (10±1)A / dm 2 The pulse frequency is maintained at 800Hz, and the duty cycle is adjusted to 35%. At this point, the film has reached a certain thickness. Appropriate adjustments are made to gradually thicken the film, reduce internal stress, and optimize the film structure. Simultaneously, the cooling system and stirring device are activated to control the electrolyte temperature between 25°C and 30°C to ensure uniform electrolyte temperature and composition, preventing local overheating that could lead to rapid film growth or defects.

[0050] The comparison of film thickness uniformity before and after the micro-arc oxidation surface treatment method for 7 series aluminum alloys described in the present invention is as follows:

[0051]

[0052] It should be noted that while the electrolyte configuration significantly impacts the micro-arc oxidation surface treatment method for 7-series aluminum alloys described herein, the primary intent of the present invention is to further improve film thickness uniformity by optimizing the micro-arc oxidation surface treatment method and steps under the same electrolyte configuration. The electrolyte configuration can be achieved using existing technical means, and the present invention only provides one embodiment of the electrolyte configuration. This should not limit the present invention's technical solution to addressing film thickness uniformity.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. 7 series aluminum alloy micro-arc oxidation surface treatment method, characterized in that: The following steps are included in sequence: Step 1: Surface pretreatment, first mechanical surface treatment, then chemical pretreatment, as follows: a. First, perform surface mechanical treatment: Perform fine mechanical treatment on the 7 series aluminum alloy workpiece, such as grinding and polishing, to reduce the surface roughness and eliminate the defects and unevenness of the original surface; use sandpaper of different grit sizes to polish gradually, and finally polish with polishing paste with a grit size of 0.5-1μm to make the surface roughness reach Ra0.1-0.3μm, providing a uniform reaction basis for micro-arc oxidation; b. Chemical pretreatment: first perform alkaline washing to remove oil stains and natural oxide film, then perform acid washing to remove alkaline washing residues and activate the surface; during alkaline washing, use 50-80g / L sodium hydroxide solution, control the temperature at 50-70°C, and treat for 3-5 minutes; acid washing uses 5%-10% nitric acid solution, and treat at room temperature for 1-2 minutes to ensure uniform surface condition and promote uniform micro-arc oxidation reaction; Step 2: Electrolyte preparation: Select an appropriate electrolyte formula based on the treatment purpose and the characteristics of the aluminum alloy. The electrolyte contains a main salt, a buffer, and additives. Use a phosphate electrolyte with a potassium dihydrogen phosphate content of 5-10 g / L, a boric acid content of 3-5 g / L, and an EDTA chelating agent content of 0.5-1.5 g / L. Accurately weigh each component in proportion, add deionized water, and stir to dissolve to ensure that the electrolyte is uniform and free of precipitation. Step 3: Micro-arc oxidation operation, including the following steps: a. Clamp the workpiece and inject the electrolyte: clamp the pretreated workpiece firmly with a fixture and place it in the micro-arc oxidation reaction tank, ensuring that the workpiece is completely immersed in the electrolyte and does not contact the tank wall and other components. Slowly inject the prepared electrolyte into the reaction tank through a pipe or funnel to reach the specified liquid level, which should generally be 5 to 10 cm higher than the top of the workpiece; b. Set process parameters and start the equipment: Set process parameters according to the aluminum alloy material, workpiece shape and film layer requirements, and set the initial voltage to 200-250V and the current density to 5-8A / dm 2 , pulse frequency 500 ~ 1000Hz, duty cycle 20% ~ 40%, processing time 20 ~ 30 minutes, after the parameter setting is completed, start the micro-arc oxidation equipment, the power supply output current and voltage, so that the workpiece surface in the electrolyte undergoes micro-arc oxidation reaction, and micro-arc discharge is observed on the workpiece surface, accompanied by sparks and bubbles; c. Process monitoring and adjustment: During the micro-arc oxidation process, the equipment operating status and process parameter changes are continuously monitored. The voltage and current fluctuations are observed through the equipment's built-in monitoring system, and the data is recorded every 5 to 10 minutes. At the same time, the electrolyte temperature changes are observed and the temperature is controlled at 20 to 40°C through the cooling system to prevent excessive temperature from affecting the film quality. Step 4: Post-processing, specifically including the following steps: a. Workpiece cleaning: After the micro-arc oxidation treatment is completed, turn off the power of the equipment, remove the workpiece from the electrolyte, and immediately rinse it in running water to remove the residual electrolyte on the surface. The rinsing time is 3 to 5 minutes to ensure that there is no electrolyte residue on the surface to prevent the residual electrolyte from corroding the film layer or affecting the subsequent performance; b. Post-treatment of the membrane layer: Use hot water sealing method to soak the cleaned workpiece in deionized water at 95-100°C for 20-30 minutes; organic coating can also be used, such as spraying epoxy resin paint to improve the protective performance and decorative properties of the membrane layer; after coating, cure at 150-180°C for 1-2 hours.

2. The micro-arc oxidation surface treatment method for 7 series aluminum alloy according to claim 1, characterized in that: In the micro-arc oxidation operation of step 3, auxiliary treatment means are also used, including ultrasonic assisted treatment and / or magnetic field assisted treatment. The specific methods are as follows: Ultrasonic-assisted treatment: set the ultrasonic frequency to 20-40kHz and the power to 100-300W; Magnetic field assisted treatment: A magnetic field is set around the micro-arc oxidation device, and the magnetic field strength is controlled at 0.1~0.5T. The ions perform spiral motion under the action of the magnetic field, which increases the uniformity on the workpiece surface and uniformly grows the film layer.

3. The micro-arc oxidation surface treatment method for 7 series aluminum alloy according to claim 1, characterized in that: In the micro-arc oxidation operation phase of step 3, the control is carried out in steps. The specific method is as follows: Stage 1: Uniform arc nucleation: The pre-treated workpiece is clamped vertically and firmly between the electrodes, ensuring that the electrode spacing is 20 mm, the initial voltage is set to 220 V, and the current density is (6 ± 1) A / dm 2 , pulse frequency 500Hz, duty cycle 25%. This stage forms uniform crystal nuclei, providing a uniform foundation for subsequent film growth; Stage 2: Stable growth: Slowly increase the voltage to 300 V and adjust the current density to (10±1) A / dm 2 , the pulse frequency was increased to 800Hz, the duty cycle was maintained at 30%, the micro-arc discharge phenomenon was closely observed to ensure uniform discharge, and the voltage and current data were recorded every 5 minutes. If the parameter fluctuation exceeded ±5%, the parameters were fine-tuned in time to maintain uniform film growth; Phase III: Slow Thickening and Optimization: Fine-tune the voltage to 320V and maintain the current density at (10±1)A / dm 2 , the pulse frequency is maintained at 800 Hz, and the duty cycle is adjusted to 35%; at the same time, the cooling system and stirring device are turned on to control the electrolyte temperature at 25-30°C to ensure uniform electrolyte temperature and composition, and prevent local overheating from causing rapid film growth or defects.

Images