A method for increasing the capacity of corrosion foil for aluminum electrolytic capacitors

Abstract

The invention discloses a method for improving the capacity of corrosion foil for aluminum electrolytic capacitors, and belongs to the technical field of aluminum electrolytic capacitors. The method is to sequentially perform pre-treatment, one-time electrolysis and multiple pores, secondary electrolysis and pore expansion, and post-treatment on electronic aluminum foil, and add one or more levels of surface modification treatment during the one-time electrolysis and multiple pores treatment, wherein the modified treatment liquid is composed of: 0.1-1.0% sodium hydroxide, 0.01-0.1% metal oxide, and the rest is water; or, the modified treatment liquid is composed of: 0.05-2wt% fluorine-containing acid, 0.01-0.1% metal oxide, and the rest is water. By introducing the surface modification treatment technology in the corrosion pore stage, the surface state of the aluminum foil in the multi-level pore stage is improved, the pore dispersion is increased, and the pores are reduced; the consistency of the corrosion foil core layer is improved, and the purpose of improving the electrostatic capacity of the corrosion foil is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum electrolytic capacitors, and in particular to a method for increasing the capacity of corrosion foil for aluminum electrolytic capacitors. Background Art

[0002] With the development of the electronics industry, aluminum electrolytic capacitors are being used more and more widely. The requirements for capacitors, especially aluminum electrolytic capacitors, in circuit design are gradually increasing. On the one hand, they require high environmental adaptability and long service life. On the other hand, the requirements for the capacity of capacitors are also increasing. The capacity of the anode foil used in capacitors is mainly determined by the corrosion stage. The technology of aluminum foil corrosion is also constantly improving with the development of related technologies and materials. From single-stage pore technology to the current mainstream multi-stage pore technology, the production efficiency and the capacity of the corrosion foil have been improved to a certain extent.

[0003] The main schemes for producing etched foil are as follows:

[0004] Existing technology 1: adopts the corrosion technology of primary pore formation and pore expansion, and the process is pre-treatment, primary pore formation, pore expansion, and post-treatment, that is, a certain concentration of phosphoric acid or a primary pore formation liquid is used as the pre-treatment liquid, a certain proportion of sulfuric acid, hydrochloric acid, and aluminum ion mixed liquid is used as the pore formation electrolyte, a certain proportion of nitric acid, phosphoric acid mixed liquid or hydrochloric acid + macromolecular additives, aluminum ions are used as the pore expansion electrolyte, and a certain concentration of nitric acid is used as the post-treatment liquid.

[0005] The etched foil produced by this technology has uneven pores, uneven core layers, and severe pores (such as Figure 1 ), resulting in low corrosion foil capacity, poor bending consistency, and low production efficiency.

[0006] Existing technology 2: adopts multi-stage pore-forming and pore-expanding corrosion technology, and the process is pre-treatment, multi-stage pore-forming (3 to 6 levels), multi-stage pore-expanding, and post-treatment, that is, a certain concentration of phosphoric acid or a first-stage pore-forming liquid is used as the pre-treatment liquid, a certain proportion of sulfuric acid, hydrochloric acid, and aluminum ion mixed liquid is used as the multi-stage pore-forming electrolyte, a certain proportion of nitric acid, phosphoric acid or nitric acid + macromolecular additives, aluminum ion mixed liquid is used as the pore-expanding electrolyte, and a certain concentration of nitric acid is used as the post-treatment liquid.

[0007] The disadvantages and problems of this solution are: the capacity and efficiency are improved to a certain extent, but due to the use of multiple holes, the holes on the surface of the corrosion foil are uneven, the length of the corrosion foil core layer is different, the dispersion of the holes is poor, and it is easy to form a hole phenomenon (such as Figure 2 ), which affects the further improvement of corrosion foil capacity. Summary of the invention

[0008] In order to solve the above-mentioned deficiencies existing in the prior art, the object of the present invention is to provide a method for improving the capacity of etching foil for aluminum electrolytic capacitors, which introduces one or more surface modification treatment technologies in the etching pore stage to improve the surface state of the aluminum foil in the pore stage, increase the dispersion of the pores in the etching foil, reduce the number of pores, and improve the consistency of the core layer of the etching foil, so as to achieve the purpose of improving the electrostatic capacitance of the etching foil.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] A method for increasing the capacity of an etched foil for an aluminum electrolytic capacitor comprises the following steps:

[0011] (1) Pretreatment: Place the annealed electronic aluminum foil with a purity of 99.99% or more in a phosphoric acid solution with a concentration of 1.0 to 8.0 wt%, treat it at 40 to 80° C. for 0.2 to 5 minutes, and then clean it, and then proceed to step (2); the pretreatment is used to clean the oil on the surface of the aluminum foil and remove the inherent oxide film on the surface of the aluminum foil;

[0012] (2) Primary electrolysis and first pore formation: The pre-treated electronic aluminum foil is subjected to a primary electrolysis and first pore formation treatment in a primary electrolyte at a treatment temperature of 60-80°C and an average current density of 0.10-1.5A / cm 2 , corrosion time 15 to 30 seconds;

[0013] (3) Electrolysis for the Nth time to form pores: Repeat the process of step (2) for N-1 (N≥2) times to form pores for the electronic aluminum foil by electrolysis for the Nth time; in the electrolysis, after each pore forming treatment, the electronic aluminum foil is subjected to surface modification treatment once or 0 times before the next pore forming treatment (no surface modification treatment is performed after the last pore forming treatment); the surface modification treatment of the electronic aluminum foil is performed at least once in the electrolysis;

[0014] (4) Secondary electrolytic pore expansion: The aluminum foil after the Nth pore expansion treatment of the primary electrolysis is subjected to secondary electrolytic pore expansion treatment in a secondary electrolyte at a treatment temperature of 70-95°C and an average current density of 0.1-0.8A / cm 2 , corrosion time 2 to 8 minutes;

[0015] (5) Post-treatment: The aluminum foil subjected to the secondary electrolytic pore expansion treatment in step (4) is subjected to chemical post-treatment in a 1.0-5.0 wt % nitric acid solution at a treatment temperature of 40-80° C. for a treatment time of 1-5 minutes. After the treatment is completed, the aluminum foil is taken out, cleaned, and dried.

[0016] In the above step (2), the composition of the primary electrolyte is: 20-50wt% sulfuric acid, 1-8wt% hydrochloric acid, 0.2-1.6wt% aluminum ions, and the rest is water; wherein the aluminum ion source is aluminum sulfate.

[0017] In the above step (3), the surface modification process is: placing the aluminum foil that has been subjected to pore formation treatment in a modification treatment solution, and subjecting it to chemical treatment or electrochemical treatment at 30 to 60° C. for 0.2 to 5 minutes.

[0018] In the above step (3), the modified treatment liquid is composed of: 0.1-1.0wt% sodium hydroxide, 0.01-0.1wt% metal oxide, and the rest is water; or, the modified treatment liquid is composed of: 0.05-2wt% fluorine-containing acid, 0.01-0.1wt% metal oxide, and the rest is water; wherein: the metal oxide is zinc oxide, manganese oxide or lead oxide that is easily enriched on the surface of aluminum foil, and the fluorine-containing acid is fluorosilicic acid.

[0019] In the above step (3), when the surface modification treatment is carried out by electrochemical method, the power treatment is direct current, the positive electrode of the power supply is connected to the aluminum foil, the negative electrode of the power supply is connected to the graphite, and the current density is 0.05-0.5A / cm 2 .

[0020] In the above step (4), the secondary electrolyte is composed of: 2-10wt% nitric acid, 0.5-2.0wt% aluminum ions, 0.2-1.5wt% phosphoric acid, and the rest is water; wherein the aluminum ion source is aluminum nitrate.

[0021] The method of the present invention adds a surface modification process, and the capacity of the prepared corrosion foil is increased by 4%-10% compared with the corrosion foil prepared by the method without surface modification treatment.

[0022] The advantages and beneficial effects of the present invention are as follows:

[0023] 1. The key technology of the method for increasing the capacity of the corrosion foil for aluminum electrolytic capacitors of the present invention is to add one or more levels of surface modification treatment in the stage of multi-level corrosion pore treatment of single electrolysis, improve the surface state of the aluminum foil in the pore stage, optimize the conditions of the aluminum foil during pore formation, increase the dispersion of pore formation, reduce the number of pores, and achieve the purpose of increasing the capacity of the corrosion foil. The capacity improvement effect can reach more than 4%.

[0024] 2. The secondary electrolytic hole expansion treatment of the present invention can increase the tunnel aperture, and the post-treatment conditions can effectively remove harmful element ions.

[0025] 3. The surface modification treatment position of the present invention is between the two pore-forming treatments from the first stage pore-forming treatment to the Nth stage pore-forming treatment, and the number of surface modification treatments is limited to any number from 1 to N-1; through the surface modification treatment, the metal ions after the metal oxide is dissolved are enriched on the surface of the aluminum foil, thereby improving the corrosion potential, increasing the dispersion of pores, and reducing the number of pores; at the same time, the stray current pores are reduced, and the stray current is gathered to improve the consistency of the pore diameter and pore length of the etched holes, which ultimately manifests as the effect of improving the corrosion capacity of the foil. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an electron microscope image of the corrosion foil produced by prior art 1; wherein: (a) is the pore surface; (b) is the cross section of the corrosion hole.

[0027] Figure 2 This is an electron microscope image of the corrosion foil produced by prior art 2; wherein: (a) is the pore surface; (b) is the cross section of the corrosion hole.

[0028] Figure 3 This is an electron microscope image of the etched foil prepared in Comparative Example 3; wherein: (a) is the pore surface; (b) is the etched hole cross section.

[0029] Figure 4 This is an electron microscope image of the etched foil prepared in Example 9; wherein: (a) is the pore surface; (b) is the etched hole cross section.

[0030] Figure 5 This is an electron microscope image of the etched foil prepared in Example 10; wherein: (a) is the pore surface; (b) is the etched hole cross section.

[0031] Figure 6 This is an electron microscope image of the etched foil prepared in Example 11; wherein: (a) is the pore surface; (b) is the etched hole cross section. DETAILED DESCRIPTION

[0032] In order to further understand the present invention, the present invention is described below in conjunction with examples, but the examples are only for further elaboration of the features and advantages of the present invention, rather than for limiting the claims of the present invention.

[0033] The present invention provides a method for increasing the capacity of an etched foil for an aluminum electrolytic capacitor, which is applicable to the current mainstream multi-stage pore etching process and can significantly increase the capacity of the etched foil. In the following embodiments and comparative examples, electronic aluminum foil that has been annealed and has a purity of more than 99.99% is used as a raw material and is processed according to the methods described in the embodiments and comparative examples.

[0034] In the following examples and comparative examples, the source of aluminum ions in the primary electrolyte is aluminum sulfate, the source of aluminum ions in the secondary electrolyte is aluminum nitrate, and the fluorine-containing acid is fluorosilicic acid.

[0035] Comparative Example 1:

[0036] Pretreatment: The electronic aluminum foil was placed in a 5.0 wt% phosphoric acid solution at 65°C for 1 minute.

[0037] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 1.05A / cm 2 .

[0038] Second electrolysis pore formation: Place in the first electrolyte for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 1.05A / cm 2 .

[0039] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0040] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0041] Embodiment 1:

[0042] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0043] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 1.05A / cm 2 .

[0044] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.4 wt % sodium hydroxide at 50° C. for 0.5 min.

[0045] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 1.05A / cm 2 .

[0046] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water; Secondary electrolytic pore expansion treatment is carried out in the solution, the temperature is 80℃, the corrosion time is 5 minutes, and the current density is 0.29A / cm 2 .

[0047] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0048] Embodiment 2:

[0049] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0050] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water; the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 1.05A / cm 2 .

[0051] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.4wt% sodium hydroxide and apply direct current at 50°C for 0.5 minutes at a current density of 0.15A / cm 2 .

[0052] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 1.05A / cm 2 .

[0053] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0054] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0055] Comparative Example 2:

[0056] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0057] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0058] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0059] The third pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0060] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0061] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0062] Embodiment 3:

[0063] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0064] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0065] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % manganese oxide and 0.5 wt % fluorine-containing acid (fluorosilicic acid) at 40° C. for 0.5 min.

[0066] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0067] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % manganese oxide and 0.5 wt % fluorine acid at 40° C. for 0.5 min.

[0068] The third pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0069] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0070] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0071] Embodiment 4:

[0072] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0073] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0074] Surface modification treatment: Place in an aqueous solution containing 0.2wt% manganese oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0075] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0076] Surface modification treatment: Place in an aqueous solution containing 0.2wt% manganese oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0077] The third pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.7A / cm 2 .

[0078] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0079] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0080] Comparative Example 3:

[0081] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0082] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0083] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0084] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0085] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0086] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0087] Post-treatment: Place in 2.7wt% nitric acid solution at 60℃ for 2 minutes. The morphology of the prepared corrosion foil is as follows Figure 3 .

[0088] Embodiment 5:

[0089] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0090] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0091] Surface modification treatment: Place in an aqueous solution containing 0.2 wt% lead oxide and 0.4 wt% sodium hydroxide at 50°C for 0.5 min.

[0092] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0093] Surface modification treatment: Place in an aqueous solution containing 0.2 wt% lead oxide and 0.4 wt% sodium hydroxide at 50°C for 0.5 min.

[0094] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0095] Surface modification treatment: Place in an aqueous solution containing 0.2 wt% lead oxide and 0.4 wt% sodium hydroxide at 50°C for 0.5 min.

[0096] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0097] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0098] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0099] Embodiment 6:

[0100] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0101] The first electrolysis pore formation: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.525A / cm 2 .

[0102] Surface modification treatment: Place in an aqueous solution containing 0.2wt% lead oxide and 0.4wt% sodium hydroxide and apply direct current at 50°C for 0.5 minutes at a current density of 0.15A / cm 2 .

[0103] The second electrolysis pore formation: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.525A / cm 2 .

[0104] Surface modification treatment: Place in an aqueous solution containing 0.2wt% lead oxide and 0.4wt% sodium hydroxide and apply direct current at 50°C for 0.5 minutes at a current density of 0.15A / cm 2 .

[0105] The third electrolysis hole: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.525A / cm 2 .

[0106] Surface modification treatment: Place in an aqueous solution containing 0.2wt% lead oxide and 0.4wt% sodium hydroxide and apply direct current at 50°C for 0.5 minutes at a current density of 0.15A / cm 2 .

[0107] The fourth electrolysis hole was placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment at a temperature of 68.0°C, a corrosion time of 25 seconds, and a current density of 0.525A / cm 2 .

[0108] Secondary electrolytic pore expansion: Placed in a solution of 6.3wt% nitric acid, 1.5wt% aluminum ions, and 0.8wt% phosphoric acid for secondary electrolytic pore expansion treatment, temperature 80°C, corrosion time 5 minutes, current density 0.29A / cm 2 .

[0109] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0110] Comparative Example 4:

[0111] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0112] The first electrolysis pore formation: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.422A / cm 2 .

[0113] The second electrolysis pore formation: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.422A / cm 2 .

[0114] The third electrolysis hole: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion for treatment, temperature 68.0℃, corrosion time 25 seconds, current density 0.422A / cm 2 .

[0115] The fourth pore formation in the first electrolysis: placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion, the temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0116] The fifth electrolysis hole was placed in a solution of 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, and 0.8wt% aluminum ion at a temperature of 68.0°C, a corrosion time of 25 seconds, and a current density of 0.422A / cm 2 .

[0117] Secondary electrolytic pore expansion: Placed in a solution of 6.3wt% nitric acid, 1.5wt% aluminum ions, and 0.8wt% phosphoric acid for secondary electrolytic pore expansion treatment, temperature 80°C, corrosion time 5 minutes, current density 0.29A / cm 2 .

[0118] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0119] Embodiment 7:

[0120] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0121] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0122] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0123] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0124] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0125] The third pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0126] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0127] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0128] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0129] The fifth pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0130] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: concentration: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0131] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0132] Embodiment 8:

[0133] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0134] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0135] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0136] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0137] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0138] The third pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0139] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0140] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0141] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0142] The fifth pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.422A / cm 2 .

[0143] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0144] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0145] Embodiment 9:

[0146] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0147] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0148] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0149] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0150] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0151] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0152] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0153] Post-treatment: Place in 2.7wt% nitric acid solution at 60℃ for 2 minutes. Figure 4 .

[0154] Embodiment 10:

[0155] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0156] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0157] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0158] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0159] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0160] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0161] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0162] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0163] Post-treatment: Place in 2.7wt% nitric acid solution at 60℃ for 2 minutes. Figure 5 .

[0164] Embodiment 11:

[0165] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0166] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0167] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0168] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0169] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0170] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0171] Surface modification treatment: Place in an aqueous solution containing 0.2 wt % zinc oxide and 0.5 wt % fluorine-containing acid at 40° C. for 0.5 min.

[0172] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0173] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0174] Post-treatment: Place in 2.7wt% nitric acid solution at 60℃ for 2 minutes. Figure 6 .

[0175] Embodiment 12:

[0176] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0177] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0178] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0179] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0180] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0181] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0182] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0183] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0184] Embodiment 13:

[0185] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0186] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0187] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0188] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0189] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0190] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0191] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0192] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment, the secondary electrolyte composition: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, the rest is water, the treatment temperature is 80℃, the corrosion time is 5 minutes, the current density is 0.29A / cm 2 .

[0193] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0194] Embodiment 14:

[0195] Pretreatment: Place in a 5.0 wt% phosphoric acid solution and treat at 65°C for 1 minute.

[0196] The first electrolysis pore formation: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0197] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0198] The second pore formation after the first electrolysis: the pore formation treatment is carried out in the first electrolyte. The first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water. The treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0199] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0200] The third pore formation of the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0201] Surface modification treatment: Place in an aqueous solution containing 0.2wt% zinc oxide and 0.5wt% fluorine acid at 50°C and apply direct current for 0.5 minutes at a current density of 0.15A / cm 2 .

[0202] The fourth pore formation in the first electrolysis: the pore formation treatment is carried out in the first electrolyte, the first electrolyte composition is: 32.5wt% sulfuric acid, 4.0wt% hydrochloric acid, 0.8wt% aluminum ion, and the rest is water, the treatment temperature is 68.0℃, the corrosion time is 25 seconds, and the current density is 0.525A / cm 2 .

[0203] Secondary electrolytic pore expansion: Place in secondary electrolyte for pore expansion treatment. The secondary electrolyte composition is: 6.3wt% nitric acid, 1.5wt% aluminum ion, 0.8wt% phosphoric acid, and the rest is water. The treatment temperature is 80℃, the corrosion time is 5 minutes, and the current density is 0.29A / cm 2 .

[0204] Post-treatment: Place in a 2.7wt% nitric acid solution at 60°C for 2 minutes.

[0205] The results of the above comparative examples and embodiments are shown in the table below:

[0206]

[0207] Based on the results of the comparative examples and the examples above, the capacity enhancement effect increases with the increase in the number of surface modification treatments, and the enhancement effect can reach more than 4%, or even more than 10%. At the same time, from the results of electron microscope photo analysis, as the number of surface modification treatments increases, the surface pore dispersion becomes better, and the number of pores also decreases with the increase in the number of surface modification treatments.

Claims

1. A method for increasing the capacity of an etched foil for an aluminum electrolytic capacitor, characterized in that: The method comprises the following steps: (1) Pretreatment: Place the annealed electronic aluminum foil with a purity of 99.99% or more in a phosphoric acid solution with a concentration of 1.0 to 8.0 wt%, treat it at 40 to 80° C. for 0.2 to 5 minutes, and then clean it, and then proceed to step (2); the pretreatment is used to clean the oil on the surface of the aluminum foil and remove the inherent oxide film on the surface of the aluminum foil; (2) First electrolysis and first pore formation: The electronic aluminum foil is subjected to a first electrolysis and first pore formation treatment in a first electrolyte at a treatment temperature of 60-80°C and an average current density of 0.10-1.5A / cm 2 , corrosion time 15 to 30 seconds; (3) Electrolysis for the Nth time to form pores: Repeat the process of step (2) for N-1 times, N ≥ 2; achieve the Nth time to form pores in the electronic aluminum foil by electrolysis; in the electrolysis, after each pore forming treatment, the electronic aluminum foil is subjected to 1 or 0 surface modification treatments before the next pore forming treatment, and no surface modification treatment is performed after the last pore forming treatment; The surface modification treatment of the electronic aluminum foil is performed at least once in the one electrolysis; (4) Secondary electrolytic pore expansion: The aluminum foil after the Nth pore expansion treatment of the first electrolysis is subjected to secondary electrolytic pore expansion treatment in the secondary electrolyte at a treatment temperature of 70-95°C and an average current density of 0.1-0.8A / cm 2 , corrosion time 2 to 8 minutes; (5) Post-treatment: The aluminum foil subjected to the secondary electrolytic pore expansion treatment in step (4) is subjected to chemical post-treatment in a 1.0-5.0 wt % nitric acid solution at a treatment temperature of 40-80° C. for a treatment time of 1-5 minutes. After the treatment is completed, the aluminum foil is taken out, cleaned, and dried; In step (3), the surface modification process is as follows: placing the aluminum foil that has undergone pore treatment in a modification treatment solution, and chemically treating or electrochemically treating it at 30-60° C. for 0.2-5 minutes; the modification treatment solution is composed of: 0.1-1.0wt% sodium hydroxide, 0.01-0.1wt% metal oxide, and the rest water; or, the modification treatment solution is composed of: 0.05-2wt% fluorine-containing acid, 0.01-0.1wt% metal oxide, and the rest water; wherein: the metal oxide is zinc oxide, manganese oxide or lead oxide that is easily enriched on the surface of the aluminum foil, and the fluorine-containing acid is fluorosilicic acid; when the surface modification treatment is performed by electrochemical treatment, the power treatment is direct current, the positive pole of the power supply is connected to the aluminum foil, the negative pole of the power supply is connected to the graphite, and the current density is 0.05-0.5A / cm 2 .

2. The method for increasing the capacity of the corrosion foil for aluminum electrolytic capacitor according to claim 1, characterized in that: In step (2), the composition of the primary electrolyte is: 20-50wt% sulfuric acid, 1-8wt% hydrochloric acid, 0.2-1.6wt% aluminum ions, and the remainder water; The aluminum ion source is aluminum sulfate.

3. The method for increasing the capacity of the corrosion foil for aluminum electrolytic capacitor according to claim 1, characterized in that: In step (4), the secondary electrolyte comprises: 2-10 wt% nitric acid, 0.5-2.0 wt% aluminum ions, 0.2-1.5 wt% phosphoric acid, and the remainder water; The aluminum ion source is aluminum nitrate.

4. The method for increasing the capacity of the corrosion foil for aluminum electrolytic capacitor according to claim 1, characterized in that: This method adds a surface modification process, and the capacity of the prepared corrosion foil is increased by more than 4% compared with the corrosion foil prepared by the method without surface modification treatment.

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