Method for pretreating aluminum foil before electrochemical corrosion hole forming so as to improve distribution uniformity of corrosion holes

Abstract

The invention belongs to the technical field of electrochemical corrosion hole forming of an aluminum foil, and discloses a method for improving the distribution uniformity of corrosion holes through pretreatment before electrochemical corrosion hole forming of the aluminum foil, which comprises the following steps: coating a layer of organic matter with good film-forming property on the surface of the aluminum foil; then the aluminum foil is placed in a high-temperature environment to be subjected to carbonization treatment, so that the surface of the aluminum foil is coated with a porous carbon film, the organic matter comprises one or more of gelatin, carrageenan and pectin, and the carbonization treatment is carried out in air with the temperature range of 400-550 DEG C. The porous carbon film prepared on the surface of the aluminum foil can efficiently guide the distribution uniformity of corrosion holes during electrochemical corrosion hole forming of the aluminum foil, and finally the specific volume of the corroded aluminum foil is remarkably increased.

Description

Technical Field

[0001] This invention belongs to the field of aluminum foil electrochemical corrosion porosimetry technology, specifically relating to a method for pretreatment of aluminum foil before electrochemical corrosion porosimetry to improve the uniformity of corrosion porosimetry distribution. Background Technology

[0002] As electronic devices continue to shrink in size, internal components also need to be reduced in size to fit within limited space. The miniaturization of aluminum electrolytic capacitors is not only a result of market demand but also an inevitable choice driven by technological advancements and efficiency improvements. Electro-etching high-purity aluminum foil with a {100} texture to increase its surface area and improve its specific capacitance is the most effective technical approach for miniaturizing aluminum electrolytic capacitors.

[0003] Currently, the electrolytic corrosion process for medium and high voltage electronic aluminum foil generally includes pretreatment, pitting corrosion, pit expansion corrosion, and post-treatment. Pretreatment refers to various physical and chemical treatments performed on the foil before electrochemical corrosion. Its purpose is to adjust the microstructure of the aluminum foil and improve its surface condition, thereby significantly improving the electrochemical corrosion performance of the material. Aluminum foil may be contaminated during manufacturing, with organic matter, oil, or other impurities adhering to its surface. Furthermore, a natural oxide film (Al2O3) may form on the aluminum foil surface. Although this natural oxide film is thin, it has a dense structure and low defect density, making it difficult for corrosive anions in the corrosion solution to penetrate. The randomness of the pitting process during corrosion leads to tunneling, co-existing pits, and clustered pits, ultimately reducing the specific capacity of the aluminum foil. Therefore, reasonable pretreatment can effectively improve the surface condition of the foil and significantly increase the specific surface area of ​​the etched foil, making it an essential and effective measure to improve the electrostatic specific capacity of the etched foil. Traditional pretreatment methods mainly include: surface cleaning, electrolytic pretreatment, rolling pretreatment, surface oxidation, surface deposition of metal elements, and masking film technology. Chinese Patent Application No. 202211500975.1 first employs a two-step combined pretreatment to improve the uniformity of corrosion porosity in aluminum foil: first, acidic solution polishing removes the oxide film from the aluminum foil; then, a self-assembled polymer film doped with corrosion inhibitors is applied to the polished aluminum foil surface, effectively reducing the co-occurrence of pits during corrosion porosity and expansion. Due to its cumbersome process and complex technology, this technique remains in the laboratory research stage, with no reports of large-scale industrial production. Chinese Patent Application No. 201210391778.0 discloses a method for pre-treating corrosion of medium- and high-voltage electronic aluminum foil boxes. The aluminum foil is placed in pure water, ammonia-containing water, or an amine-containing aqueous solution at a temperature of 70-100℃ for treatment, or subjected to appropriate heat treatment after treatment. After treatment, a hydrated oxide film with uniformly distributed defects is generated on the aluminum foil surface; this improves the uniformity of porosity and reduces the probability of tunneling and co-occurrence. Chinese patent application No. 101425392A discloses a pretreatment process that improves the specific capacity of aluminum foil by adding 0.001-0.0025% of a bismuth- or indium-containing compound, or a mixture thereof, to a pretreatment solution of acid, alkali, mixed acid, or mixed alkali. While this patented technology is simple and easy to implement in industrial production, its effect on improving specific capacity is limited. Therefore, a more optimized pretreatment scheme is urgently needed to overcome the current technological bottlenecks. Summary of the Invention

[0004] The purpose of this invention is to provide a method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution. This method aims to solve the technical problem of tunneling pits and clustered pits caused by the randomness of corrosion during the corrosion process, which in turn affects the specific volume of the anode foil.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0006] A method for improving the uniformity of corrosion pit distribution by pretreatment before electrochemical corrosion of aluminum foil, characterized in that the pretreatment involves coating the surface of the aluminum foil with an organic material with good film-forming properties, and then placing it in a high-temperature environment for carbonization treatment to obtain a porous carbon film coating on the surface of the aluminum foil.

[0007] Furthermore, the organic matter is composed of gelatin, carrageenan, and pectin.

[0008] Furthermore, the molar ratio of the gelatin, carrageenan and pectin is 1:(3-5):(6-8).

[0009] Furthermore, the molar ratio of the gelatin, carrageenan, and pectin is 1:4:7.

[0010] Furthermore, the total concentration of the gelatin, carrageenan, and pectin is 5-10 wt.%.

[0011] Furthermore, the total concentration of the gelatin, carrageenan, and pectin is 8 wt.%.

[0012] Further, the organic matter is dissolved in water to obtain a solution, and then the aluminum foil is immersed in the above solution and coated with an organic film. The coated aluminum foil is then carbonized.

[0013] Furthermore, the coated aluminum foil is placed in air at a temperature range of 400-550℃ for carbonization treatment for 10-30 minutes, with a heating rate of 5℃ / min. After carbonization treatment, the surface of the aluminum foil is coated with a porous carbon film.

[0014] Furthermore, the coated aluminum foil is placed in air at a temperature range of 475°C for carbonization treatment for 20 minutes at a heating rate of 5°C / min. After carbonization treatment, the surface of the aluminum foil is coated with a porous carbon film.

[0015] Furthermore, the pretreated aluminum foil is subjected to electrochemical etching in 3.5M sulfuric acid + 0.5M hydrochloric acid to generate corrosion pits on the surface.

[0016] Compared with the prior art, the present invention has the following technical advantages:

[0017] 1. The three-component organic compound achieves a synergistic film-forming effect of "1+1+1>3", overcoming the performance limitations of single / two-component pretreatment.

[0018] In existing technologies, traditional pretreatment methods either use a single organic material for film formation or only employ two-component compounding, both of which suffer from membrane structure defects: single gelatin films are prone to cracking due to uneven shrinkage caused by thermal decomposition; single carrageenan films have excessive hydrophilicity leading to increased pores after drying; and single pectin films have insufficient strength and uneven thickness. Two-component compounding cannot simultaneously meet the requirements of different pore sizes, either lacking macropores that affect electrolyte permeation, lacking mesopores that hinder ion transport, or lacking micropores that reduce specific surface area. This invention innovatively uses a compound of gelatin, carrageenan, and pectin in a specific molar ratio. The three components form a stable three-dimensional network structure through intermolecular hydrogen bonds and ionic bonds. Gelatin provides basic mechanical strength, carrageenan optimizes the hydrophilicity and hydrophobicity of the membrane layer, and pectin enhances the uniformity of film formation, effectively compensating for the defects of single or two-component film formation. The resulting organic membrane has good film-forming properties and a stable structure, laying a solid foundation for subsequent carbonization to form a high-quality porous carbon membrane, achieving film formation effects far exceeding those of single or two-component systems.

[0019] 2. After carbonization, a three-level gradient through-hole structure is formed, solving the core problem that traditional pretreatment cannot guide the uniform distribution of corrosion pores.

[0020] Existing pretreatment methods, whether acid polishing + self-assembled film, hydrated oxide film preparation, or the addition of bismuth / indium compounds, fail to create a guiding structure with a clear pore size gradient. This results in random penetration paths for corrosive anions during the corrosion pitting process, easily leading to tunnel pores, co-existing pores, and clustered pits. This invention precisely constructs a porous carbon film with a three-tiered gradient of "micropores-mesopores-macropores" through the synergistic pyrolysis of three organic components: gelatin pyrolysis forms 0.5-2 nm micropores, providing high specific surface area adsorption sites; carrageenan decomposes to form 2-50 nm mesopores, serving as rapid ion transport channels; and pectin decomposes to form 50-200 nm macropores, enhancing electrolyte wetting and deep penetration capabilities. This hierarchical pore structure acts like a "template," efficiently guiding anions in the corrosion solution to orderly penetrate the aluminum foil surface, forcing corrosion pitting along the pore locations of the carbon film, fundamentally suppressing the randomness of corrosion, significantly improving the uniformity of pit distribution, and completely solving the problems of co-existing pores and clustered pits that are difficult to overcome with traditional techniques.

[0021] 3. The process is simple and easy to industrialize, overcoming the bottleneck of complex pretreatment technologies that are difficult to apply on a large scale.

[0022] While some pretreatment methods in existing technologies can improve the porosity to some extent, they have significant process defects. For example, the two-step combined pretreatment (acid polishing + self-assembled polymer film) is cumbersome and complex, requiring multi-step reaction control, and is currently only at the laboratory stage, unable to meet the needs of large-scale industrial production. While the method of adding bismuth / indium compounds is simple, the improvement in specific capacity is limited. The pretreatment method of this invention has an extremely simple process, requiring only the aluminum foil to be immersed in a three-component organic aqueous solution to complete the coating. Subsequent carbonization only requires control of key parameters such as temperature, time, and heating rate, without the need for complex equipment investment or precise process control. This process is highly compatible with existing aluminum foil etching production lines and can be directly integrated into existing production processes without large-scale equipment modifications. This lowers the threshold for industrial application while achieving a significant improvement in specific capacity, balancing technical effectiveness and industrial feasibility.

[0023] 4. The carbon film adheres tightly to the aluminum foil surface and exhibits strong stability, solving the problems of easy peeling and failure of traditional pretreatment films.

[0024] Existing pretreatment films (such as self-assembled polymer films and hydrated oxide films) have weak adhesion to the aluminum foil surface. Under the strong acid and alkali environment and electric field of subsequent electrochemical corrosion, the film is prone to peeling, decomposition, or failure, making it difficult to sustain its pore-guiding effect. This invention uses high-temperature carbonization to completely transform organic films into porous carbon films. The carbon film forms a stable bond with the aluminum foil surface through both physical adsorption and chemical bonding: on the one hand, the porous structure of the carbon film forms a mechanical interlock with the aluminum foil surface, enhancing film adhesion; on the other hand, slight interfacial reactions that may occur during carbonization further improve the bonding strength between the film and the aluminum foil. Furthermore, the carbon film itself has excellent chemical stability and corrosion resistance, and is not easily decomposed or destroyed in the subsequent sulfuric acid-hydrochloric acid corrosion system. It can maintain its complete structure and guiding function throughout the pore-guiding process, ensuring the stability and durability of the pretreatment effect, far exceeding the service life and effectiveness of traditional films.

[0025] 5. Adaptable to different specifications of anode foil, offering greater technical versatility and flexible adjustment options.

[0026] Existing pretreatment solutions are often highly targeted, only suitable for specific types or specifications of aluminum foil, with limited room for adjustment. For example, some solutions are only applicable to aluminum foil of specific purity, or can only meet specific corrosion current densities and corrosion time requirements. When the aluminum foil specifications or corrosion process parameters change, the pretreatment effect will significantly decrease. This invention, by flexibly adjusting the molar ratio and total concentration of gelatin, carrageenan, and pectin, can precisely control the pore size distribution, porosity, and film thickness of the porous carbon film, thereby adapting to the needs of different specifications of anode foil. For fine-pore corrosion requiring high specific capacity, the ratio can be adjusted to enhance the micropore to mesopore ratio; for high-current-density processes requiring rapid pore formation, the proportion of macropores can be optimized to improve the electrolyte penetration rate. This flexible adjustability allows this pretreatment method to adapt to the aluminum foil corrosion process requirements of different manufacturers and application scenarios, possessing stronger technical versatility and market application value, breaking through the limitation of single adaptability of traditional pretreatment technologies. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] The purpose of this invention is to solve the technical problem of tunneling holes and clustered pits caused by the randomness of corrosion during the corrosion pitting process, which in turn affects the specific volume of the anode foil. The invention provides a method for pre-treating aluminum foil before electrochemical corrosion pitting to improve the uniformity of the corrosion pit distribution. The method uses organic materials, wherein the molar ratio of gelatin, carrageenan and pectin is 1:(3-5):(6-8), more preferably 1:4:7.

[0029] The total concentration of gelatin, carrageenan and pectin is 5-10 wt.%, preferably 8 wt.

[0030] It is worth noting that by adjusting the ratio of different components, the present invention essentially finds a balance between film-forming characteristics and stability, in order to meet the needs of anode foils of different specifications (such as corrosion current density and corrosion time requirements).

[0031] The treatment effect for a single component is as follows:

[0032] Gelatin alone can form a basic organic film. However, during high-temperature carbonization, the rapid thermal decomposition rate can easily lead to uneven film shrinkage, resulting in cracks or localized peeling.

[0033] Carrageenan alone has strong hydrophilicity, and during the drying stage, rapid evaporation of moisture can easily form pores, reducing the continuity of the carbon film.

[0034] Using only pectin results in low gel strength, easy flow during coating leading to uneven thickness, and a loose structure after carbonization.

[0035] The treatment effect of the two-component combination is as follows:

[0036] The combination of gelatin and carrageenan results in only micropores (0.5–2 nm) formed by gelatin and mesopores (2–50 nm) formed by carrageenan, completely lacking the macropores (50–200 nm) contributed by pectin, thus preventing the electrolyte from deeply penetrating to the aluminum foil surface.

[0037] The combination of gelatin and pectin: The micropores of gelatin and the macropores of pectin lack the 2-50nm mesopore channels constructed by carrageenan. The tortuosity of the ion transport path is >2.5 (≈1.8 for the three-component system), and the ion stacking is severely activated at high rates.

[0038] The combination of carrageenan and pectin relies on the mesopores of carrageenan and the macropores of pectin, but lacks the 0.5–2 nm high specific surface area micropores generated by gelatin, resulting in a reduction in specific surface area.

[0039] This invention also provides a method for obtaining a porous carbon film coating on the surface of aluminum foil by carbonization treatment in a high-temperature environment, comprising:

[0040] Carbonization is carried out in air at a temperature range of 400-550℃ for 10-30 minutes, with a heating rate of 5℃ / min.

[0041] Technical principle of the invention:

[0042] This invention relates to a method for pre-treating aluminum foil before electrochemical etching to improve the uniformity of pore distribution. The method involves pre-treating the aluminum foil surface with organic materials, including gelatin, carrageenan, and pectin, to form a layer of organic material with good film-forming properties. Subsequently, the aluminum foil is subjected to high-temperature carbonization to obtain a porous carbon film coating. The synergistic effect of the components achieves significantly better technical results than traditional processes. Specifically, the gelatin molecular chain contains a large number of amino (-NH2) and carboxyl (-COOH) groups, which cross-link through hydrogen bonds to form a three-dimensional network structure, providing initial mechanical strength for the coating and contributing to the basic network for film formation. Furthermore, during pyrolysis at 300-400℃, the gelatin peptide bonds break, generating volatile gases (NH3, CO2), forming 0.5-2 nm micropores. Carrageenan contains sulfate ester groups (-OSO3). - At low temperatures of 200-300℃, the pectin decomposes to produce SO2 gas, forming mesopores of 2-50nm, which provide ion transport channels. Pectin is rich in galacturonic acid, and when it decomposes at 250-350℃, the carboxyl groups decarboxylate to produce CO / CO2, forming macropores of 50-200nm, which enhances the wettability of the electrolyte and forms a three-level gradient connection of micropores, mesopores and macropores.

[0043] In this embodiment of the invention, organic materials including gelatin, carrageenan, and pectin are pretreated and coated onto the surface of aluminum foil to form a layer of organic material with good film-forming properties. The organic material is compounded in a specific ratio to produce a synergistic effect of "1+1+1>3". Subsequently, it is placed in a high-temperature environment for carbonization treatment to obtain a porous carbon film coating on the surface of the aluminum foil. The porous carbon film can efficiently guide the uniformity of the distribution of corrosion pits during the electrochemical corrosion of aluminum foil, and ultimately significantly improve the specific volume of the corroded aluminum foil.

[0044] The following detailed description uses specific examples to illustrate a method for pretreatment of aluminum foil before electrochemical etching to improve the uniformity of pore distribution. Unless otherwise specified, the experimental methods used in the following examples are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0045] In the electrochemical corrosion of anodic aluminum foil, aluminum foil with a purity of 99.99%, a thickness of 120 μm, and a cubic texture content of more than 95% is used.

[0046] Example 1

[0047] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:3:6 in water.

[0048] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0049] Example 2

[0050] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:8 in water.

[0051] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0052] Example 3

[0053] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0054] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0055] Example 4

[0056] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:5:7 in water.

[0057] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0058] Example 5

[0059] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0060] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 400°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0061] Example 6

[0062] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0063] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 500°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0064] Example 7

[0065] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0066] Aluminum foil samples were immersed in an organic solution with a total concentration of 8 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 550°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0067] Example 8

[0068] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0069] Aluminum foil samples were immersed in an organic solution with a total concentration of 5 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0070] Example 9

[0071] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0072] Aluminum foil samples were immersed in an organic solution with a total concentration of 10 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0073] Example 10

[0074] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0075] Aluminum foil samples were immersed in an organic solution with a total concentration of 10 wt.%, and then an organic film was coated onto the surface of the aluminum foil. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 10 min at a heating rate of 5°C / min. This was followed by etching to create pits, enlargement etching, post-treatment, and a 520°C formation treatment.

[0076] Example 11

[0077] In this embodiment, the aluminum foil forming additive is composed of gelatin, carrageenan and pectin, with a molar ratio of 1:4:7 in water.

[0078] Aluminum foil samples were immersed in an organic solution with a total concentration of 10 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 30 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0079] Comparative Example 1

[0080] The aluminum foil was immersed in a traditional pretreatment solution of 1.5M HCl at 70°C for 180 seconds, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0081] Comparative Example 2

[0082] In this comparative example, the aluminum foil forming additive is composed of gelatin and pectin, with a molar ratio of 1:7, dissolved in water.

[0083] Aluminum foil samples were immersed in an organic solution of gelatin and pectin with a total concentration of 5 wt.%, and then coated with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520 V formation treatment.

[0084] Comparative Example 3

[0085] Aluminum foil samples were immersed in a 2 wt.% carrageenan organic solution, followed by coating the aluminum foil surface with an organic film. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520V formation treatment.

[0086] Comparative Example 4

[0087] Aluminum foil samples were immersed in a pectin organic solution with a total concentration of 2 wt.%, and then an organic film was coated onto the surface of the aluminum foil. The coated aluminum foil was then subjected to carbonization treatment at a high temperature of 475°C for 20 min at a heating rate of 5°C / min, followed by etching to create pores, enlargement etching, post-treatment, and 520V formation treatment.

[0088] The samples prepared in Examples 1-11 and Comparative Examples 1-4 were tested according to the industry standard SJ / T 11140-1997 for electrode foils for aluminum electrolytic capacitors. The test results are shown in Table 1.

[0089]

[0090] In the preliminary experiments of this invention, the following series of studies were conducted on the effects of the type, concentration and ratio of pretreated organics, treatment temperature and treatment time on subsequent corrosion and porosity in the soaking treatment conditions. The experimental conditions and test results are shown in Table 2 below. It should be noted that the following comparative examples are all single-factor variation experiments based on the process of Example 3, including changing the molar ratio of gelatin, carrageenan and pectin, or changing the total concentration of organic solution, or changing the treatment temperature, or changing the treatment time, or changing the type of organic adhesive based on the process of Example 3.

[0091]

[0092]

[0093] In summary, as shown in Tables 1-2 above, the embodiments of the present invention significantly increase the specific volume by immersing aluminum foil samples in a solution of gelatin, carrageenan and pectin under suitable conditions, followed by carbonization treatment in a high-temperature environment to obtain a porous carbon film coating on the aluminum foil surface, and then etching to create pores.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for pretreating aluminum foil before electrochemical etching to improve the uniformity of etched pit distribution, characterized in that, The pretreatment involves coating the aluminum foil surface with a film-forming organic material, followed by carbonization at a suitable temperature to obtain a porous carbon film coating on the aluminum foil surface.

2. The method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution according to claim 1, characterized in that, The organic compound is composed of gelatin, carrageenan and pectin.

3. The method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution, as described in claim 2, is characterized in that... The molar ratio of the gelatin, carrageenan and pectin is 1:(3-5):(6-8).

4. The method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution according to claim 3, characterized in that, The molar ratio of gelatin, carrageenan, and pectin is 1:4:

7.

5. The method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution according to claim 4, characterized in that, The total concentration of the gelatin, carrageenan and pectin is 5-10 wt.%.

6. The method for pretreatment of aluminum foil before electrochemical etching to improve the uniformity of etched pit distribution, as described in claim 5, is characterized in that... The total concentration of the gelatin, carrageenan and pectin is 8 wt.%.

7. The method for pretreatment of aluminum foil before electrochemical corrosion to improve the uniformity of corrosion pit distribution, as described in claim 1 or 2, is characterized in that... The organic matter is dissolved in water to obtain a solution. The aluminum foil is then immersed in the solution and coated with an organic film. The coated aluminum foil is then carbonized.

8. The method for pretreatment of aluminum foil before electrochemical etching to improve the uniformity of etch pit distribution, as described in claim 7, is characterized in that... The coated aluminum foil is placed in air at a temperature range of 400-550℃ for carbonization treatment for 10-30 minutes, with a heating rate of 5℃ / min. After carbonization treatment, the surface of the aluminum foil is coated with a porous carbon film.

9. The method for pretreatment of aluminum foil before electrochemical etching to improve the uniformity of etched pit distribution, as described in claim 8, is characterized in that... The coated aluminum foil was placed in air at a temperature of 475°C for carbonization for 20 minutes at a heating rate of 5°C / min. After carbonization, the aluminum foil surface was coated with a porous carbon film.

10. The method for pretreatment of aluminum foil before electrochemical etching to improve the uniformity of etch pit distribution, as described in claim 1, is characterized in that... The pretreated aluminum foil was subjected to electrochemical etching in 3.5M sulfuric acid + 0.5M hydrochloric acid to generate corrosion pits on the surface.

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