Post-annealing surface cleaning method for improving electrochemical performance of aluminum foil for electrolytic capacitor

Abstract

The invention belongs to the technical field of chemical industry, and particularly relates to an annealed surface cleaning method for improving electrochemical performance of an aluminum foil for an electrolytic capacitor. Comprising the following steps of: uncoiling an annealed aluminum foil coiled material for the electrolytic capacitor, and sequentially carrying out alkali washing, water washing and drying. The alkaline washing condition is that the pH value of the alkaline solution is 8-12, the temperature is 30-80 DEG C, and the alkaline washing time is 5-50 s; the washing condition is that the water temperature is 40-80 DEG C, and the washing time is 5-50 seconds; the drying condition is that the temperature is 70-150 DEG C, and the drying time is 2-20 seconds. By the adoption of the method, carbonized residues, uneven oxide layers, aluminum powder and the like on the surface of the finished aluminum foil can be effectively and thoroughly removed, a thinner and more uniform oxide layer is regenerated, after the obtained finished electronic aluminum foil roll is corroded, surface hole forming is more uniform, and the service life of the finished electronic aluminum foil roll is prolonged. The hole forming density is higher, and the hole forming area proportion and the single hole number proportion are higher.

Description

Technical Field

[0001] This invention belongs to the technical field of the chemical industry, specifically relating to a method for surface cleaning after annealing to improve the electrochemical performance of aluminum foil for electrolytic capacitors. Background Technology

[0002] As the electronics industry develops towards intelligence and energy efficiency, photovoltaics, optoelectronics, frequency converters, LED lighting, and electric vehicles are placing higher demands on the capacitance, surface properties, and other performance characteristics of aluminum electrolytic capacitors. Aluminum foil, as the core raw material for manufacturing aluminum electrolytic capacitors, is a key factor determining their performance and quality. With the continuous development of etching processes for aluminum electrolytic capacitors, and considering cost and environmental factors, existing aluminum foil production processes can no longer fully meet the needs of etching manufacturers. These manufacturers often complain about oily surfaces, heavy aluminum powder, and uneven oxide film thickness, leading to high pretreatment difficulty and poor product capacitance stability. Product research has revealed that during the pretreatment of aluminum foil for electrolytic capacitors in China, the presence of residual aluminum powder, rolling oil, and additives on the material surface causes uneven surface layers and oxide film thickness, resulting in uneven pore lengths during etching. This significantly affects the final aluminum foil surface quality and porosity characteristics, leading to uneven pore formation, low pore quantity, and uneven pore lengths during etching, resulting in lower specific capacitance and larger deviations in the final product. The main process for producing aluminum foil for aluminum electrolytic capacitors involves using high-purity aluminum raw materials with a purity of 99.996%, adding trace elements such as Fe, Si, Cu, Zn, Mn, and Ga to promote corrosion, casting them into ingots, and then going through more than ten processes such as homogenization, hot rolling, cold rolling, intermediate annealing, cold rolling, cleaning, finished product annealing, and rewinding to obtain electronic aluminum foil. Downstream customers then use processes such as etching and formation to obtain foil for capacitors.

[0003] Because the aluminum foil used in aluminum electrolytic capacitors has high purity, it has low hardness. During rolling, aluminum powder is prone to falling off and surface damage. Furthermore, since cold working often uses a mixture of rolling oil and additives as a lubricant, the viscosity is high and it is difficult to clean with conventional cleaning methods. As a result, after the finished product is annealed, the surface residual lubricant carbonizes, aluminum powder sinters, and the oxide layer thickens (up to 50-200nm). The oxide film thickness is uneven. Traditional cleaning before annealing cannot remove the new contaminants generated during annealing. As a result, in the subsequent corrosion process, surface impurities hinder electrolyte penetration, reduce specific capacitance, aluminum powder falls off and contaminates the corrosion equipment, and uneven oxide layer causes pitting defects. Summary of the Invention

[0004] To address the problems of residual lubricant carbonization, aluminum powder sintering, oxide layer thickening, and uneven oxide film thickness distribution on the surface of aluminum foil after annealing in existing technologies, this invention provides a post-annealing surface cleaning method to improve the electrochemical performance of aluminum foil for electrolytic capacitors. Compared to the traditional production process of aluminum foil for electrolytic capacitors: ingot casting → rolling → cleaning → annealing → winding, the innovation of this method lies mainly in the change of the cleaning process and the cleaning medium. The production process adopted in this method is: ingot casting → rolling → annealing → cleaning → winding. That is, this method adds a multi-stage cleaning process after the final annealing process of electronic aluminum foil, simultaneously removing carbonized residues, loose oxide layers, and aluminum powder, significantly improving surface activity, thereby improving the uniformity of porosity and reducing the variation in oxide film thickness.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0006] An annealing-based surface cleaning method for improving the electrochemical performance of aluminum foil for electrolytic capacitors can address problems such as low surface cleanliness and uneven oxide layer thickness leading to poor electrochemical performance in aluminum foil for aluminum electrolytic capacitors.

[0007] The preparation process of annealed aluminum foil rolls for electrolytic capacitors is as follows: First, slabs with a thickness of 500-600 mm are cast using a slab casting process. Then, they are hot-rolled into 3-8 mm thick coils through 13-19 passes. Next, they are cold-rolled into 0.100-0.150 mm thick aluminum foil rolls through 5-10 passes. Finally, they undergo annealing at 500-580℃ for 10 hours. Following this, multiple cleaning processes are performed, including the following steps:

[0008] (1) The cleaning process involves the material roll passing through the unwinding mechanism and entering the alkaline washing tank. It is placed in an alkaline liquid with a pH of 8-12 (the alkaline solution is a mixture of sodium carbonate, sodium bicarbonate, and sodium gluconate; the pH is adjusted by regulating the proportion of sodium carbonate), at a temperature of 30-80℃, for a washing time of 5-50 seconds (including soaking and rinsing time). The alkaline tank contains 1-3 sets of brush rollers and a spray head to clean the material surface. The optimal conditions are a pH of 8-10, a temperature of 40-60℃, and an alkaline washing time of 20-40 seconds. Under these conditions, carbonized residues and oxide films on the surface of the soft electronic aluminum foil roll can be effectively removed without causing significant aluminum foil etching.

[0009] (2) After exiting the alkali tank, use a squeeze roller to squeeze out the surface alkali and then enter the water washing tank. The water washing tank contains pure water at a temperature of 40~80℃. The material surface is rinsed by spraying for 5~50s. This includes 1~3 sets of brush rollers and one spray head to brush and wash the material surface. The optimal conditions are a water washing temperature of 50~60℃ and a spraying time of 10~15s. Under these conditions, pure water can completely wash away the residual alkali and reaction products on the surface of the strip, effectively ensuring the cleanliness of the material roll surface and preventing the residue of alkali and reactants from affecting the subsequent corrosion process.

[0010] (3) After exiting the washing box, use a squeezing roller to squeeze out the residual moisture on the surface, and then put it into the drying box. Dry it with hot air at 70~150℃ for 2~20s. After drying, the surface is inspected by a defect detector, and then it is wound up by a winding mechanism. The optimal conditions are drying at 80~120℃ for 10~15s. Under these conditions, the residual moisture on the surface of the roll can be completely dried, and wrinkles will not occur during the winding process due to the high drying temperature.

[0011] The cleaning method of the present invention can achieve the following beneficial effects:

[0012] (1) Compared with conventional electronic aluminum foil cleaning, the cleaning medium is 40# or 60# kerosene, which poses a certain fire risk. This invention uses water-based weak alkaline cleaning solution for cleaning, which has no fire risk and the cleaning agent cost is lower.

[0013] (2) The method of the present invention is used to clean the soft roll of finished electronic aluminum foil. Compared with the traditional production process, an uneven oxide film and some residual carbon formed by the annealing of rolling oil additives will be generated after annealing. This method can effectively remove the carbonized residue, uneven oxide layer and aluminum powder on the surface of finished aluminum foil, and regenerate a thinner and more uniform oxide layer, which is easier for customers to remove the surface oxide layer in the future.

[0014] (3) The method of the present invention is used to clean the soft roll of finished electronic aluminum foil. Compared with the pretreatment of acid solutions such as phosphoric acid and sulfuric acid commonly used by downstream corrosion customers, this cleaning technology will not form pores on the aluminum foil surface. The surface microstructure is smoother and will not have an adverse effect on subsequent corrosion pore formation.

[0015] (4) The electronic aluminum foil finished product soft roll is cleaned by the method of the present invention. After the electronic aluminum foil finished product roll is etched, the surface pores are more uniform, the pore density is greater, and the pore area ratio and single pore number ratio are higher. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cleaning device of the present invention;

[0017] In the diagram: 1-Alkali washing tank, 2-Water washing tank, 3-Drying tank, 4-Alkali spray head, 5-Alkali tank brush roller, 6-Alkali tank squeeze roller, 7-Water washing spray head, 8-Water washing tank brush roller, 9-Water washing tank squeeze roller.

[0018] Figure 2 The figures show the oxide film thickness detection results for the examples and comparative examples;

[0019] Figure 3 Figures showing the experimental results of oxide film removal in the examples and comparative examples;

[0020] Figure 4 Here is a scanning electron microscope image of the corrosion test surface in Example 1;

[0021] Figure 5 Here is a scanning electron microscope image of the corrosion experiment surface in Example 2;

[0022] Figure 6 Here is a scanning electron microscope image of the corrosion test surface in Example 3;

[0023] Figure 7 Here is a scanning electron microscope image of the corrosion experiment surface in Comparative Example 2;

[0024] Figure 8 Here is a scanning electron microscope image of the corrosion experiment surface in Comparative Example 3;

[0025] Figure 9 Here is a scanning electron microscope image of the corrosion experiment surface in Comparative Example 4;

[0026] Figure 10 Here is a scanning electron microscope image of the corrosion experiment surface in Comparative Example 5;

[0027] Figure 11 The image shows a scanning electron microscope (SEM) image of the corrosion test surface in Comparative Example 6. Detailed Implementation

[0028] To further understand the present invention, the following description is based on embodiments. However, the embodiments are only for further illustrating the features and advantages of the present invention, and are not intended to limit the technical solutions of the present invention.

[0029] This invention provides a post-annealing surface cleaning method for improving the electrochemical performance of aluminum foil used in electrolytic capacitors. This method modifies the conventional electronic aluminum foil production process. Specifically, it involves casting ingots (containing trace elements Fe (10-30ppm), Si (10-30ppm), Cu (20-100ppm), and the remainder Al) into ingots approximately 500-600mm thick. These ingots are then processed into hot-rolled coils of 3-8mm thickness using 13-19 passes (total hot-rolling yield ≥98%), followed by 5-10 passes of cold rolling (total cold-rolling yield ≥95%) to produce finished coils of 0.100-0.150mm thickness. Finally, the coils undergo annealing at 500-580℃ for 10 hours, followed by cleaning. The cleaning process is adjusted to occur after the finished product annealing. Furthermore, a new cleaning system is implemented... Figure 1 As shown, it includes an alkaline washing tank, a water washing tank, and a drying tank. The alkaline washing tank and the water washing tank contain sprayers and brush rollers, which can continuously spray the material surface at a pressure of 10-30 bar. The cleaning process includes three main steps: weak alkaline cleaning, pure water cleaning, and drying. The weak alkaline cleaning can effectively remove oxide film, aluminum powder, carbide residues, etc. from the surface of aluminum foil, improving the surface consistency of aluminum foil for electrolytic capacitors. Then, the weak alkaline residue is rinsed off the product surface by pure water cleaning. Finally, the moisture on the product surface is evaporated by drying.

[0030] The specific process is as follows: After annealing, the aluminum foil rolls enter the alkaline washing tank, are sprayed with alkaline solution at 10-30 bar, and then cleaned by brush rollers. After exiting the alkaline washing tank, the aluminum foil is squeezed dry by squeezing rollers. After squeezing dry, the aluminum foil enters the water washing tank, is sprayed with water at 10-30 bar, and then cleaned by brush rollers. After exiting the water washing tank, the aluminum foil is squeezed dry by squeezing rollers. After squeezing dry, the aluminum foil enters the drying oven for hot air drying, and then is wound up.

[0031] Example 1: Proceed as follows:

[0032] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 500℃ for 10h. The soft electronic aluminum foil rolls (normal thickness is 0.130mm) after annealing are cleaned.

[0033] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing box with a pH of 8 and an alkaline solution (a mixture of sodium carbonate, sodium bicarbonate and sodium gluconate) temperature of 40°C. It is soaked for 10 seconds, sprayed for 10 seconds, and then brushed with a brush roller and squeezed dry.

[0034] (3) In a pure water rinsing tank at 50°C, spray for 10 seconds, and then brush and squeeze dry the surface.

[0035] (4) Dry in an 80°C drying oven for 10 seconds. After drying, inspect the surface with a defect detector and then rewind using a winding mechanism.

[0036] Example 2: Proceed as follows:

[0037] (1) After the electronic aluminum foil finished rolls are cast, hot rolled and cold rolled, they are annealed at 550°C for 10 hours. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130 mm) after the finished annealing are cleaned.

[0038] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing box with a pH value of 10 and an alkaline solution (a mixture of sodium carbonate, sodium bicarbonate and sodium gluconate) temperature of 60°C, soaks for 30 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0039] (3) Spray for 15 seconds in a pure water rinsing tank at 60℃, and then brush and squeeze dry the surface.

[0040] (4) Dry in a drying oven at 120°C for 15 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0041] Example 3: Proceed as follows:

[0042] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0043] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing box with a pH of 9 and an alkaline solution (a mixture of sodium carbonate, sodium bicarbonate and sodium gluconate) temperature of 50°C, soaks for 20 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0044] (3) Spray for 12 seconds in a pure water rinsing tank at 50℃, and then brush and squeeze dry the surface.

[0045] (4) Dry in a drying oven at 100°C for 12 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0046] Comparative Example 1: Proceed as follows:

[0047] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0048] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing tank with a pH value of 13 and an alkaline solution temperature of 85°C, soaks for 70 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0049] (3) Spray for 12 seconds in a pure water rinsing tank at 50℃, and then brush and squeeze dry the surface.

[0050] (4) Dry in a drying oven at 100°C for 12 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0051] Comparative Example 2: Proceed as follows:

[0052] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0053] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing box with a pH value of 8 and an alkaline solution temperature of 20°C, soaks for 3 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0054] (3) Spray for 12 seconds in a pure water rinsing tank at 50℃, and then brush and squeeze dry the surface.

[0055] (4) Dry in a drying oven at 100°C for 12 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0056] Comparative Example 3: Proceed as follows:

[0057] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0058] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing tank with a pH value of 9 and an alkaline solution temperature of 50°C, soaks for 20 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0059] (3) In a pure water rinsing tank at 30°C, spray for 5 seconds, and then brush and squeeze dry the surface.

[0060] (4) Dry in a drying oven at 120°C for 15 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0061] Comparative Example 4: Proceed as follows:

[0062] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0063] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing tank with a pH value of 9 and an alkaline solution temperature of 50°C, soaks for 20 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0064] (3) Spray for 12 seconds in a pure water rinsing tank at 50℃, and then brush and squeeze dry the surface.

[0065] (4) Dry in a drying oven at 60°C for 5 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0066] Comparative Example 5: Proceed as follows:

[0067] (1) The finished electronic aluminum foil rolls after slab casting, hot rolling and cold rolling are annealed at 580℃ for 10h. The soft electronic aluminum foil rolls (with a conventional thickness of 0.130mm) after annealing are cleaned.

[0068] (2) After the material roll is unwound by the unwinding mechanism, it enters the alkaline washing box with a pH value of 13 and an alkaline solution temperature of 85°C, soaks for 5 seconds, sprays for 10 seconds, and is then cleaned with a brush roller and squeezed dry.

[0069] (3) Spray for 12 seconds in a pure water rinsing tank at 50℃, and then brush and squeeze dry the surface.

[0070] (4) Dry in a drying oven at 100°C for 12 seconds. After drying, inspect the surface with a defect detector and then rewind it using a winding mechanism.

[0071] Comparative Example 6: Proceed as follows:

[0072] (1) The finished electronic aluminum foil rolls (with a standard thickness of 0.130mm) after slab casting, hot rolling and cold rolling are cleaned with 60# kerosene (purchased from Huai'an Qingjiang Petrochemical Co., Ltd.). The cleaning is mainly done by spraying kerosene at 50-80℃ in the cleaning box and brushing with a brush roller. Then, the rolls are squeezed dry and dried to obtain the cleaned rolls.

[0073] (2) The cleaned rolls are annealed at 500-580℃ for 10 hours to obtain finished electronic aluminum foil rolls.

[0074] Comparative Example 7: Proceed as follows:

[0075] (1) After the electronic aluminum foil finished product roll (conventional thickness is 0.130mm) after slab casting, hot rolling and cold rolling, it enters the alkaline washing box with pH value of 10 and alkaline solution temperature of 60℃ after passing through the uncoiling mechanism, soaks for 30s, sprays for 10s, and then squeezes the surface dry after brushing with a brush roller.

[0076] (2) In a pure water rinsing tank at 60℃, spray for 15 seconds, and then brush and squeeze dry the surface.

[0077] (3) Dry in a drying oven at 120℃ for 15 seconds. After drying, inspect the surface with a defect detector and then rewind using a winding mechanism.

[0078] (4) The cleaned rolls are annealed at 550°C for 10 hours to obtain finished electronic aluminum foil rolls.

[0079] The three conditions in Examples 1-3 above correspond to the optimal condition lower limit, optimal condition upper limit, and optimal condition middle limit of the present invention, respectively. The six conditions in Comparative Examples 1-6 are: Comparative Example 1: ultra-high intensity alkaline washing treatment, optimal normal water washing, and optimal drying; Comparative Example 2: low intensity alkaline washing treatment, optimal water washing, and optimal drying; Comparative Example 3: optimal intensity alkaline washing treatment, low intensity water washing, and optimal drying; Comparative Example 4: optimal intensity alkaline washing treatment, optimal intensity water washing, and low intensity drying; Comparative Example 5: high intensity alkaline washing treatment, optimal normal water washing, and optimal drying; Comparative Example 6: conventional electronic aluminum foil cleaning process product. Comparative Example 7: optimal condition middle limit cleaning, followed by finished product annealing. The products produced by the above examples and comparative examples were analyzed by oxide film thickness detection, oxide film removal detection, and surface porosity detection. The oxide film thickness detection data comparison is shown in Table 1 and... Figure 2 .

[0080] Table 1 Comparison of oxide film thickness test data

[0081] (1) Oxide film thickness (converted by specific volume detection, the equipment is LCR digital bridge): The average oxide film thicknesses of Examples 1, 2 and 3 are 4.63nm, 4.08nm and 4.22nm respectively. The lateral dispersion (the range of thickness of 13 points divided by the maximum value of the 13 points × 100%) is within 5%. Comparative Example 1 has no data because the alkaline solution corrosion rate is fast and the reaction is violent, resulting in foil breakage. Comparative Example 7 was not tested because coarse grains (abnormal grain growth) appeared after annealing. The oxide film thickness dispersion of the other comparative examples is above 6%, which shows that the oxide film distribution is uneven. The oxide film thickness of Comparative Example 6 is the highest after conventional oil cleaning.

[0082] (2) Oxide film removal (the oxide film was determined by testing its volume in a phosphoric acid solution using an LCR digital bridge): The oxide film removal data results are shown below. Figure 3 As can be seen from the figure, Examples 1, 2, 3 and Comparative Example 5 have a fast removal speed, while conventional oil cleaning has the slowest removal speed.

[0083] (3) Surface porosity detection and analysis: Initial corrosion (using a mixture of 7 equivalents of sulfuric acid and 2 equivalents of hydrochloric acid, temperature 70℃, energized for 3s, current density 0.5A / cm2): The surface porosity detection results are shown in Table 2. The surface scanning electron microscope results after corrosion of Examples 1-3 and Comparative Examples 2-6 are shown in Table 2. Figures 4-11 The data shows that Examples 1, 2, and 3 have the highest porosity. Comparative Example 1 had no data because the foil broke during the experiment due to a violent reaction. The porosity of the other comparative examples was relatively low. Example 2 had the largest porosity area, and Example 1 had the largest percentage of single porosity.

[0084] Table 2 Surface Porosity Analysis Results

[0085] As can be seen from the above embodiments and comparative examples, when using the surface cleaning method for improving the electrochemical performance of aluminum foil for electrolytic capacitors according to the present invention, the aluminum foil for electrolytic capacitors produced under the optimal conditions, namely, after unwinding, is placed in an alkaline washing box with a pH of 8-10, immersed at 40-60℃ for 10-30 seconds, squeezed dry, placed in a pure water rinsing box at 50-60℃, sprayed for 10-15 seconds, squeezed dry, and dried in a drying box at 80-120℃ for 10-15 seconds before being wound up, corresponding to Examples 1, 2, and 3, the aluminum foil for electrolytic capacitors produced by this method has a more uniform surface, a thinner oxide film, less dispersion, easier oxide film removal, and a higher pore density of corrosion pores, which greatly increases the effective surface area of ​​the aluminum foil, thereby significantly improving its electrochemical specific capacitance and making it more conducive to the production of high specific capacitance electronic aluminum foil products. Meanwhile, in Comparative Example 1, the high pH value and temperature of the alkaline solution and the long reaction time caused the foil to break, making normal production impossible. In Comparative Example 7, the alkaline cleaning treatment was performed on the aluminum foil in a hard state, which released the stress on the aluminum foil surface and resulted in uneven stress distribution. This caused abnormal grain growth during the high-temperature annealing of the finished product, failing to meet the product quality requirements. Therefore, such phenomena should be avoided when using this method.

[0086] In this invention, by adopting the recommended processing method, compared with the traditional oil cleaning method before annealing of finished electronic aluminum foil, carbonized residues, loose oxide layers and aluminum powder can be effectively removed, significantly improving surface activity, thereby improving the uniformity of pores and reducing dispersion.

Claims

1. A method for surface cleaning after annealing to improve the electrochemical performance of aluminum foil for electrolytic capacitors, characterized in that: The annealed aluminum foil rolls for electrolytic capacitors are subjected to multiple cleaning processes, including the following steps: (1) After the annealed aluminum foil roll is unwound, the surface is alkali washed. The pH value of the alkali washing solution is 8~12, the temperature is 30~80℃, and the alkali washing time is 5~50s. (2) After alkaline washing, the aluminum foil is surface rinsed at a water temperature of 40~80℃ for 5~50s. (3) Dry the rinsed aluminum foil at a temperature of 70~150℃ for 2~20s.

2. The cleaning method according to claim 1, characterized in that: The alkaline washing described in step (1) is carried out in an alkaline washing tank. The alkaline washing tank is equipped with 1 to 3 sets of brush rollers and a spray head. During the alkaline washing process, the aluminum foil is first soaked, then sprayed, and the surface of the aluminum foil is cleaned.

3. The cleaning method according to claim 1, characterized in that: The pH value of the alkaline washing solution in step (1) is 8~10, the temperature is 40~60℃, and the alkaline washing time is 20~40s.

4. The cleaning method according to claim 1, characterized in that: The rinsing in step (2) is carried out in a water washing tank containing pure water. The water washing tank is equipped with 1 to 3 sets of brush rollers and a spray head. During the rinsing process, the aluminum foil surface is sprayed and brushed.

5. The cleaning method according to claim 1, characterized in that: The rinsing conditions described in step (2) are: water temperature 50~60℃, rinsing time 10~15s.

6. The cleaning method according to claim 1, characterized in that: The drying process described in step (3) is carried out in a drying oven at a temperature of 80~120℃ for 10~15s.

7. The cleaning method according to claim 1, characterized in that: After the alkaline washing described in step (1) and the rinsing described in step (2), the residual liquid on the surface is squeezed out using the squeezing rollers set in the alkaline washing tank and the water washing tank before proceeding to the next process.

8. The cleaning method according to claim 1, characterized in that: The method for preparing the annealed aluminum foil roll for electrolytic capacitors is as follows: First, it is cast into a plate ingot with a thickness of 500~600mm, then hot rolled into a hot rolled coil with a thickness of 3~8mm through 13~19 passes, and then cold rolled into an aluminum foil roll with a thickness of 0.100-0.150mm through 5~10 passes, and then annealed at 500~580℃ for 10h.

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