JP3959680B2

JP3959680B2 - Etching method of aluminum electrolytic capacitor anode foil

Info

Publication number: JP3959680B2
Application number: JP2002118046A
Authority: JP
Inventors: 博司岡崎; 博宣花本; 滋朗市村
Original assignee: Hitachi AIC Inc
Current assignee: Hitachi AIC Inc
Priority date: 2002-04-19
Filing date: 2002-04-19
Publication date: 2007-08-15
Anticipated expiration: 2022-04-19
Also published as: JP2003318069A

Description

【０００１】
【発明の属する技術分野】
本発明は、アルミニウム電解コンデンサ用電極箔のエッチング方法に関するもので、特に160wV以上の中高圧用陽極箔の製造方法に関するものである。
【０００２】
【従来の技術】
アルミニウム陽極箔はコンデンサの小形化をはかるために、有効表面積を拡大したものが使用され、その製造方法は、種々の研究がされているが、一般に、アルミニウム箔を電気的、電気化学的な電解工程によるエッチングによって、ピットと呼ばれるトンネル状の孔を形成し、電気的、電気化学的あるいは無電解にてエッチングしてピット孔を拡大するという工程が施されている。
実際の生産では、ピット形成からピット径拡大まで１回のエッチング工程でおこなうと工程途中の制御が難しので、アルミニウム箔を数種類の異なるエッチング槽に連続的に挿入し、給電ロールを介しての電流印加による電解エッチングによってピットを形成する段、電解あるいは無電解によってピット孔を拡大する段、最終洗浄する段等を複数段設けることにより製造されている。
【０００３】
【発明が解決しようとする課題】
しかしながら、従来の方法では、電解エッチングによってピットを形成させていたため、生産能力を向上しようとすると、通電電流を大きくしなければならず、一定以上の電流は、発熱のため設備上印加できないこととなり、製造工程における単位時間、１台あたりの製造能力が制限されていた。さらに、流れる電流が多くなるとアルミ箔の幅方向で電流密度の大きさがばらつき、従って、均一にエッチング処理されず、エッチング倍率がばらつくという問題が発生しやすい。
この製造工程おいては、アルミニウム原箔から効率よく均一にピットを発生させることが、単位面積あたりの静電容量を高くする重要な点となり、また、製造装置１台あたりの生産能力を高めることが、近年強く要望されている低コスト化への重要な課題となる。
また、装置を新設する場合においては、製造装置の初期投資も、通電を必要とすることから、整流器など電装部への費用がかかり、製品の単価を引き上げる要因となっており、その後の運転費用についても、ピット形成工程における電気費用は必須となっていた。
近年、アルミニウム電解コンデンサの小形化および低コスト化が強く要望されており、これらの要望を満たすためには、このアルミニウム電解コンデンサに使用しているアルミニウム箔の実効表面積を効率よく向上させ小形化を促進し、さらに低コスト化には、製造装置１台あたりの生産能力を高めることが不可欠である。
【０００４】
本発明は上記従来の問題点を解決するもので、アルミニウム電解コンデンサ用電極箔を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、本発明は、少なくとも、自然酸化皮膜を除去する第１段階と、ピットを形成させる第２段階と、ピット孔を拡大させる第３段階とからなるエッチング処理により製造されるアルミニウム電解コンデンサ用陽極箔の多段製造方法において、ピットを発生させる少なくとも１段からなるピット形成工程のうち、少なくとも１段のエッチング液中に、Ｍｇ，Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｕ，Ｇｅ，Ｎｂ，Ｍｏ，Ｐｄ，Ａｇ，Ｉｎ，Ｓｎ，Ｓｂ，Ｗ，Ｔｌ，Ｐｂの各金属の、パルミチン酸やステアリン酸などの脂肪酸塩、オキシ硫酸塩、硫酸塩、硫酸アンモニウム塩、塩酸塩、硝酸塩、サリチル酸塩、モリブデン酸塩、乳酸塩、硫化物、プロポキシやペンチルオキシなどのアルコキシ誘導体のうち少なくとも１種類以上の金属化合物と塩素イオンを含ませることにより、電気的、電気化学的処理を施さず、ピット形成工程を無電解でし、表面積拡大をおこなうものである。
また、ピット形成工程における無電解化が可能となることで、完全なる無電解ではなく電流を印加する場合においても、電流が小さくても大電流を印加した場合と同様の効果が得られる。
本発明により、実用的に使用できるレベルを確保し、尚且つエッチング工程途中の制御を容易におこなうことが可能となり、160wV以上の中高圧領域における生産性向上と特性改善がはかれる。
【０００６】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
まず、アルミニウム箔は純度９９.９%以上で、厚みが３０μｍから３００μｍ程度の軟質アルミニウム箔を使用する。
エッチングとしては、まず、第１段階として、アルミニウム箔の表面に形成されている自然酸化被膜を除去するために、５０℃〜９０℃範囲の液温の塩酸や硫酸またはそれらの混酸等の酸性水溶液中に、100秒程度浸漬する。
次に、第２段階として、アルミニウム箔をピットと呼ばれるトンネル状の孔を形成するために、５０℃〜９０℃範囲の液温の塩酸や硫酸またはそれらの混酸等の酸性水溶液中に、Ｍｇ，Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｕ，Ｇｅ，Ｎｂ，Ｍｏ，Ｐｄ，Ａｇ，Ｉｎ，Ｓｎ，Ｓｂ，Ｗ，Ｔｌ，Ｐｂの各金属の、パルミチン酸やステアリン酸などの脂肪酸塩、オキシ硫酸塩、硫酸塩、硫酸アンモニウム塩、塩酸塩、硝酸塩、サリチル酸塩、モリブデン酸塩、乳酸塩、硫化物、プロポキシやペンチルオキシなどのアルコキシ誘導体などの金属化合物を添加したエッチング液に、５０秒〜３００秒程度浸漬する。金属化合物は単独でもよいし、複数添加してもよい。
また、このとき生産能力をより向上させるために、完全なる無電解ではなく電気的、電気化学的処理を施すために電流を印加してもよい。
次に、第３段階として、ピット孔を拡大するために、５０℃〜９０℃範囲の液温の塩酸や硫酸や硝酸またはそれらの混酸等の酸性水溶液中に、１分から１０分程度浸漬する。
エッチングされた箔は洗浄の後、化成工程にて必要な耐電圧が得られる電圧で化成処理をおこなう。
【０００７】
【実施例】
以下、本発明の実施例について説明する。
【０００８】
〔実施例１〕純度99.99%、厚み110μｍの軟質アルミニウム箔を85℃の酸性水溶液(塩酸10%、硫酸20%の水溶液)中に、120秒浸漬し、前段のエッチング処理をおこなった後、80℃の酸性水溶液(塩酸10%、硫酸40%の水溶液)中に、表１に示す金属化合物を添加して、箔を150秒浸漬し、無電解処理でピットを発生させ中段のエッチング処理をおこない、次に、80℃、5%の塩酸水溶液中に浸漬し、5分間浸漬してピット孔拡大の最終段のエッチング処理をおこなう。エッチング処理後の箔は、60℃の１mol/l硝酸水溶液で１分間洗浄後、90℃、12wt%のホウ酸水溶液にて300Vの化成処理をおこなった。
【０００９】
〔実施例２〕純度99.99%、厚み110μｍ、幅500mmの軟質アルミニウム箔コイルを用い、従来の電極箔製造装置において、前段エッチング槽に85℃の酸性水溶液(塩酸10%、硫酸20%の水溶液)を、中段エッチング槽に表１に示す金属化合物を添加した80℃の酸性水溶液(塩酸10%、硫酸40%の水溶液)を、後段エッチング槽に、80℃、5%の塩酸水溶液を3l/minの補給量で補給し、前段、中段、後段槽における浸漬時間がそれぞれ、120秒、150秒、5分となるように、製造装置の箔速度を調整し、洗浄工程は従来装置の工程にて洗浄をおこない、通常の製造で実施される形態のエッチド箔を製造した。
製造したエッチド箔は、12wt%のホウ酸水溶液の化成工程にて400Vの化成処理をおこなった。
【００１０】
〔従来例１〕純度99.99%、厚み110μｍの軟質アルミニウム箔を85℃の酸性水溶液(塩酸10%、硫酸20%の水溶液)中に120秒浸漬し、上記の前段エッチング処理をおこなった後、80℃の酸性水溶液(塩酸10%、硫酸40%の水溶液)中に電流密度0.3A/cm²の直流を150秒印加して中段のエッチング処理をおこない、次に、80℃、5%の硝酸水溶液中に浸漬し、かつ電流密度0.5A/cm²の直流を200秒間印加して後段のエッチング処理をおこなう。エッチング処理後の箔は、60℃の１mol/l硝酸水溶液で１分間洗浄後、90℃ 12wt%のホウ酸水溶液にて300Vの化成処理をおこなった。
【００１１】
〔従来例２〕純度99.99%、厚み110μｍ、幅500mmの軟質アルミニウム箔コイルを用い、電極箔製造装置において、前段エッチング槽に85℃の酸性水溶液(塩酸10%、硫酸20%の水溶液)を、中段エッチング槽に80℃の酸性水溶液(塩酸10%、硫酸40%の水溶液)を、後段エッチング槽に、80℃、5%の硝酸水溶液を、それぞれ、3l/minの補給量で補給し、前段、中段、後段槽における浸漬時間がそれぞれ、120秒、150秒、200秒となるよう、製造装置の箔速度を調整し、中段においては、電流密度0.3A/cm2の直流を、後段においては、電流密度0.5A/cm2の直流をそれぞれ印加し、ピット形成、ピット径拡大をおこなう。洗浄工程は従来装置の工程にて洗浄をおこなった。
製造したエッチド箔は、12wt%のホウ酸水溶液の化成工程にて400Vの化成処理をおこなった。
【００１２】
【表１】

上記した従来例および本発明の各実施例による箔を各試料について静電容量と静電容量のばらつきと折り曲げ強度(200g荷重、丸鉄芯に釣り下げ、その直径)を測定した結果を表２と３に示す。
【００１３】
【表２】

【００１４】
【表３】

【００１５】
ピット形成工程を、エッチング液に金属化合物を1種以上添加した無電解工程でおこなっても、従来と比較し同等以上の特性が確保できる。これにより、従来の設備も大きな変更を必要とせず使用可能で、ピット形成工程にかかる電気代が削減され、さらに、新設の設備においても、ピット形成工程に必要な通電設備が必要でなくなる。
また、ピット形成工程における無電解化が可能となったことで、完全なる無電解ではなく電流を印加する場合においても、電流が小さくても大電流を印加した場合と同様の効果が得られることが示唆された。
また、無電解によるエッチングのため、アルミ箔の幅方向のばらつきはばらつきにくく、従って、エッチング倍率がばらつきにくく、均一にエッチング処理されやすい。
【００１６】
【発明の効果】
以上のように、本発明のアルミニウム電解コンデンサ用陽極箔の製造方法によれば、エッチング液中に均一に溶解したこれらの金属化合物は、触媒として作用し、通電を必要とすることなく、また、小電流でもアルミニウムに効率よくピットを発生させるため、電極箔の表面積は拡大されて、その静電容量のアップをはかることができ、尚且つ、無電解のピット形成製造工程が可能となるため、生産性を向上させる際の電気的設備上の制約を考慮する必要がないため、生産能力を向上させることができる。また、従来の設備も大きな変更を必要とせず使用可能で、新設の設備においても、ピット形成工程に必要な通電設備が必要でなくなり、単位面積あたりの陽極箔製造にかかる費用を安価に抑えることができる。また、ピット形成工程における無電解化が可能となったことで、完全なる無電解ではなく電流を印加する場合においても、電流が小さくても大電流を印加した場合と同様の効果が得られることと、流れる電流がないか少ないので、アルミ箔の幅方向で電流密度の大きさのばらつきが抑えられる。従って、エッチング倍率のばらつきが少なく、均一にエッチング処理されやすい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method for an electrode foil for an aluminum electrolytic capacitor, and more particularly to a method for producing a medium-high pressure anode foil of 160 wV or more.
[0002]
[Prior art]
In order to reduce the size of a capacitor, an aluminum anode foil having an enlarged effective surface area is used, and its manufacturing method has been studied in various ways. In general, an aluminum foil is electrically and electrochemically electrolyzed. A tunnel-like hole called a pit is formed by etching according to the process, and the process of enlarging the pit hole by etching electrically, electrochemically or electrolessly is performed.
In actual production, if one etching process is performed from pit formation to pit diameter enlargement, control during the process is difficult, so aluminum foil is continuously inserted into several different etching tanks, and the current through the feed roll It is manufactured by providing a plurality of stages, such as a stage for forming pits by electrolytic etching by application, a stage for expanding pit holes by electrolysis or electroless, a stage for final cleaning, and the like.
[0003]
[Problems to be solved by the invention]
However, in the conventional method, pits are formed by electrolytic etching. Therefore, in order to improve the production capacity, the energizing current must be increased, and a current exceeding a certain level cannot be applied to the equipment due to heat generation. The production capacity per unit time in the production process was limited. Furthermore, when the flowing current increases, the current density varies in the width direction of the aluminum foil. Therefore, the etching process is not uniformly performed, and the etching magnification is likely to vary.
In this manufacturing process, efficiently and uniformly generating pits from the aluminum foil is an important point for increasing the capacitance per unit area, and also increasing the production capacity per manufacturing device. However, this is an important issue for cost reduction that has been strongly demanded in recent years.
In addition, when a new device is installed, the initial investment of the manufacturing equipment also requires energization, which incurs costs for the electrical components such as rectifiers, which increases the unit price of the product. In addition, the electric cost in the pit formation process has become essential.
In recent years, there has been a strong demand for miniaturization and cost reduction of aluminum electrolytic capacitors. In order to satisfy these demands, the effective surface area of the aluminum foil used in the aluminum electrolytic capacitors is efficiently improved to reduce the size. In order to promote and further reduce the cost, it is essential to increase the production capacity per manufacturing apparatus.
[0004]
The present invention solves the above-mentioned conventional problems, and an object thereof is to provide an electrode foil for an aluminum electrolytic capacitor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is manufactured by an etching process including at least a first stage for removing a natural oxide film, a second stage for forming pits, and a third stage for expanding pit holes. In the multi-stage manufacturing method for an anode foil for an aluminum electrolytic capacitor , Mg, Ti, V, Cr, Mn, Fe, Cu are contained in at least one stage of the pit forming process including at least one stage for generating pits. , Ge, Nb, Mo, Pd, Ag, In, Sn, Sb, W, Tl, Pb , fatty acid salts such as palmitic acid and stearic acid, oxysulfate, sulfate, ammonium sulfate, hydrochloride, At least one or more of alkoxy derivatives such as nitrate, salicylate, molybdate, lactate, sulfide, propoxy and pentyloxy By including the above metal compound and chlorine ions , the surface area is expanded without electrolysis or electrochemical treatment and by making the pit formation process electroless .
In addition, since the electroless formation in the pit formation process is possible, the same effect as when a large current is applied can be obtained even when a current is applied instead of a complete electroless process.
According to the present invention, a practically usable level can be ensured, and control in the middle of the etching process can be easily performed, and productivity and characteristics can be improved in a medium and high pressure region of 160 wV or higher.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
First, the aluminum foil is a soft aluminum foil having a purity of 99.9% or more and a thickness of about 30 μm to 300 μm.
As etching, first, as a first step, an acidic aqueous solution such as hydrochloric acid, sulfuric acid, or a mixed acid thereof having a liquid temperature in the range of 50 ° C. to 90 ° C. is used to remove the natural oxide film formed on the surface of the aluminum foil. Soak in for about 100 seconds.
Next, as a second step, in order to form tunnel-like holes called pits in the aluminum foil, Mg, in an acidic aqueous solution such as hydrochloric acid, sulfuric acid or a mixed acid thereof having a liquid temperature in the range of 50 ° C. to 90 ° C. Fatty acid salts such as palmitic acid and stearic acid, oxysulfuric acid of each metal of Ti, V, Cr, Mn, Fe, Cu, Ge, Nb, Mo, Pd, Ag, In, Sn, Sb, W, Tl, and Pb 50 seconds to 300 seconds in an etching solution to which a metal compound such as a salt, sulfate, ammonium sulfate, hydrochloride, nitrate, salicylate, molybdate, lactate, sulfide, alkoxy derivatives such as propoxy and pentyloxy is added Immerse to the extent. A metal compound may be individual and may add multiple.
At this time, in order to further improve the production capacity, an electric current may be applied to perform an electrical or electrochemical treatment instead of complete electroless.
Next, as a third stage, in order to enlarge the pit hole, the substrate is immersed in an acidic aqueous solution such as hydrochloric acid, sulfuric acid, nitric acid or a mixed acid thereof having a liquid temperature in the range of 50 to 90 ° C. for about 1 to 10 minutes.
The etched foil is subjected to a chemical conversion treatment after cleaning at a voltage at which a required withstand voltage is obtained in the chemical conversion step.
[0007]
【Example】
Examples of the present invention will be described below.
[0008]
[Example 1] A soft aluminum foil having a purity of 99.99% and a thickness of 110 μm was immersed in an acidic aqueous solution (aqueous solution of 10% hydrochloric acid and 20% sulfuric acid) at 85 ° C. for 120 seconds. Add the metal compounds shown in Table 1 in an acidic aqueous solution at 10 ° C (aqueous solution of 10% hydrochloric acid and 40% sulfuric acid), immerse the foil for 150 seconds, generate pits by electroless treatment, and perform the middle etching treatment Next, the substrate is immersed in a 5% hydrochloric acid aqueous solution at 80 ° C. and immersed for 5 minutes to perform the final etching process for expanding the pit holes. The foil after the etching treatment was washed with a 1 mol / l aqueous nitric acid solution at 60 ° C. for 1 minute, and then subjected to a chemical conversion treatment at 300 ° C. with a 12 wt% boric acid aqueous solution at 90 ° C.
[0009]
[Example 2] Using a soft aluminum foil coil with a purity of 99.99%, a thickness of 110μm, and a width of 500mm, an acidic aqueous solution of 85 ° C (aqueous solution of 10% hydrochloric acid and 20% sulfuric acid) was used in the former etching tank in a conventional electrode foil manufacturing apparatus. 80 ° C acidic aqueous solution (10% hydrochloric acid, 40% sulfuric acid aqueous solution) with the metal compound shown in Table 1 added to the middle etching tank, and 3 liter / min of 80 ° C, 5% hydrochloric acid aqueous solution to the latter etching tank. Adjust the foil speed of the production equipment so that the immersion time in the front, middle, and rear tanks is 120 seconds, 150 seconds, and 5 minutes, respectively, and the cleaning process is the process of the conventional equipment Cleaning was performed to produce an etched foil of the form that is implemented in normal production.
The manufactured etched foil was subjected to a chemical conversion treatment of 400 V in a chemical conversion process of a 12 wt% boric acid aqueous solution.
[0010]
[Conventional Example 1] A soft aluminum foil having a purity of 99.99% and a thickness of 110 μm was immersed in an acidic aqueous solution (85% hydrochloric acid, 20% sulfuric acid) for 120 seconds and subjected to the above-mentioned pre-etching treatment. Apply a direct current with a current density of 0.3 A / cm ² for 150 seconds in an acidic aqueous solution at 10 ° C (aqueous solution of hydrochloric acid 10%, sulfuric acid 40%), and then perform the middle stage etching treatment, then 80 ° C, 5% nitric acid aqueous solution It is immersed in the substrate and a direct current having a current density of 0.5 A / cm ² is applied for 200 seconds to perform the subsequent etching process. The foil after the etching treatment was washed with a 1 mol / l nitric acid aqueous solution at 60 ° C. for 1 minute, and then subjected to a chemical conversion treatment at 300 ° C. with a boric acid aqueous solution at 90 ° C. and 12 wt%.
[0011]
[Conventional example 2] Using an aluminum foil coil with a purity of 99.99%, a thickness of 110 μm, and a width of 500 mm, in an electrode foil manufacturing apparatus, an acidic aqueous solution (hydrochloric acid 10%, sulfuric acid 20% aqueous solution) at 85 ° C. A 80 ° C acidic aqueous solution (10% hydrochloric acid, 40% sulfuric acid aqueous solution) was supplied to the middle etching tank, and 80 ° C and 5% nitric acid aqueous solution was supplied to the latter etching tank at a replenishment rate of 3 l / min. The foil speed of the production apparatus was adjusted so that the immersion time in the middle and rear tanks was 120 seconds, 150 seconds, and 200 seconds, respectively.In the middle stage, a direct current with a current density of 0.3 A / cm2 was used. Applying direct current of current density 0.5A / cm2 respectively, pit formation and pit diameter expansion. The cleaning process was performed in the process of the conventional apparatus.
The manufactured etched foil was subjected to a chemical conversion treatment of 400 V in a chemical conversion process of a 12 wt% boric acid aqueous solution.
[0012]
[Table 1]

Table 2 shows the results of measuring the capacitance and the variation in capacitance and the bending strength (200 g load, hanged down to a round iron core, the diameter) of the foils according to the above-described conventional examples and the embodiments of the present invention for each sample. And 3
[0013]
[Table 2]

[0014]
[Table 3]

[0015]
Even if the pit formation process is performed in an electroless process in which one or more metal compounds are added to the etching solution, the same or better characteristics can be ensured as compared with the prior art. As a result, the conventional equipment can be used without requiring major changes, and the electricity cost for the pit formation process is reduced. Furthermore, even in the newly installed equipment, the power supply equipment necessary for the pit formation process is not required.
In addition, since the electroless process in the pit formation process has become possible, the same effect as when a large current is applied can be obtained even when a current is applied rather than a complete electroless process. Was suggested.
In addition, because of electroless etching, variations in the width direction of the aluminum foil are unlikely to vary, and accordingly, the etching magnification is unlikely to vary and the etching process is easily performed uniformly.
[0016]
【The invention's effect】
As described above, according to the method for producing an anode foil for an aluminum electrolytic capacitor of the present invention, these metal compounds that are uniformly dissolved in an etching solution act as a catalyst without requiring energization, In order to efficiently generate pits in aluminum even with a small current, the surface area of the electrode foil can be increased, the capacitance can be increased, and an electroless pit formation manufacturing process becomes possible. Since it is not necessary to consider the restrictions on electrical facilities when improving productivity, the production capacity can be improved. In addition, the conventional equipment can be used without requiring major changes, and even in the newly installed equipment, the current-carrying equipment necessary for the pit formation process is no longer necessary, and the cost of manufacturing anode foil per unit area can be kept low. Can do. In addition, since the electroless process in the pit formation process has become possible, the same effect as when a large current is applied can be obtained even when a current is applied rather than a complete electroless process. Since there is little or no current flowing, variations in current density in the width direction of the aluminum foil can be suppressed. Accordingly, there is little variation in the etching magnification, and uniform etching processing is easy.

Claims

In a multistage manufacturing method of an anode foil for an aluminum electrolytic capacitor manufactured by an etching process comprising at least a first stage for removing a natural oxide film, a second stage for forming pits, and a third stage for expanding pit holes In the pit forming process including at least one stage for generating pits , Mg, Ti, V, Cr, Mn, Fe, Cu, Ge, Nb, Mo, Pd, Ag, In are contained in at least one stage of etching solution. , Sn, Sb, W, Tl, Pb , fatty acid salts such as palmitic acid and stearic acid, oxysulfate, sulfate, ammonium sulfate, hydrochloride, nitrate, salicylate, molybdate, lactate, Including at least one metal compound and chloride ion among sulfides, alkoxy derivatives such as propoxy and pentyloxy Thus, a method for producing an anode foil for an aluminum electrolytic capacitor of 160 wV or more, in which pits are formed in an electroless process without increasing the surface area without performing electrical or electrochemical treatment.

In a multistage manufacturing method of an anode foil for an aluminum electrolytic capacitor manufactured by an etching process comprising at least a first stage for removing a natural oxide film, a second stage for forming pits, and a third stage for expanding pit holes In the pit formation process consisting of at least one stage for generating and forming pits , Mg, Ti, V, Cr, Mn, Fe, Cu, Ge, Nb, Mo, Pd, Ag are contained in at least one stage of the etching solution. , In, Sn, Sb, W, Tl, Pb , fatty acid salts such as palmitic acid and stearic acid, oxysulfate, sulfate, ammonium sulfate, hydrochloride, nitrate, salicylate, molybdate, lactic acid It contains at least one metal compound and chloride ion among salts, sulfides, alkoxy derivatives such as propoxy and pentyloxy. In addition, a method for producing an anode foil for an aluminum electrolytic capacitor of 160 wV or higher, in which pits are formed by combining electrical and electrochemical treatment to increase the surface area.