JP5117673B2 - Aluminum material for electrolytic capacitor electrode, method for producing electrode material for electrolytic capacitor, anode material for aluminum electrolytic capacitor, and aluminum electrolytic capacitor - Google Patents

Description

  The present invention relates to an aluminum material for electrolytic capacitor electrodes, a method for producing an electrode material for electrolytic capacitors, an anode material for aluminum electrolytic capacitors, and an aluminum electrolytic capacitor.

  In this specification, the term “aluminum” is used to include both aluminum and its alloys, and the aluminum material includes at least an aluminum foil, an aluminum plate, and a molded body thereof.

  In recent years, with the miniaturization of electronic devices, there has been a demand for improvement in electrostatic capacity of aluminum foil for electrolytic capacitor electrodes incorporated in electronic devices.

  Usually, an aluminum material used for an electrolytic capacitor electrode is etched in order to increase the surface expansion ratio and improve the capacitance. Then, the etch pit formed by the etching process has a higher surface area ratio as the density becomes higher and uniform and deep. Therefore, various treatments are performed on the aluminum material as a pre-process of the etching treatment in order to improve etching suitability.

  For example, a hydration process before final annealing, a crystalline oxide film formation process in final annealing, an oxidation process before final annealing, and the like (for example, Patent Documents 1 and 2).

  Also, a method for obtaining a high capacitance by specifying the contents of various elements such as Zn, Mn, Cu, Fe, Si, Ga, Pb, Mg, B, V, Ti, Zr, Ni, C, P, etc. Have also been proposed (for example, Patent Documents 3 and 4).

Furthermore, the saturation current density and the current density rapid increase potential of the aluminum foil after the final annealing are defined, and the oxide film within the defined range is suppressed in surface dissolution and has a high capacitance (for example, Patent Document 5). There is also a report that a foil having a pitting corrosion potential in an aluminum material of −760 to −735 mV and a surface having a pitting corrosion potential of 10 to 60 mV lower than this has a uniform deep etching (for example, Patent Document 6).
Japanese Patent Publication No. 58-34925 Japanese Patent Laid-Open No. 3-122260 JP-A-2-270928 JP-A-5-5145 JP-A-11-36032 JP-A-4-143242

  However, the above-described efforts alone have not sufficiently satisfied the recent demand for higher capacitance of electrolytic capacitors. In particular, there is room for improvement with respect to the technology for controlling the content of trace elements described in Patent Document 3 and Patent Document 4.

  In addition, the regulation of saturation current density and current density rapid increase potential described in Patent Document 5 regulates the characteristics of the oxide film on the surface layer, and the relationship with trace amounts of elements in the aluminum material has been studied. Absent.

  In Patent Document 6, the importance of making the pitting corrosion potential of the surface layer lower than the inside is emphasized. However, in recent etching, the surface layer is often removed as a pretreatment before electrolytic etching. In addition to the control of the surface layer, internal control has become important, and control of only the surface layer has not been sufficient for increasing the capacity.

  Further, in recent years, the demand for cost reduction along with high capacitance has been increasing more and more in etching manufacturers, and an aluminum material that can achieve both high capacitance and low cost is desired.

  In view of such a technical background, the present invention has a high density of deep etch pits even when a large amount of aluminum lump purified by a segregation method is cheaper than aluminum lump refined by a three-layer electrolysis method. Aluminum material for electrolytic capacitor electrode, method for producing electrode material for electrolytic capacitor, anode material for aluminum electrolytic capacitor, and aluminum electrolytic capacitor that can be generated uniformly and surely increase the area expansion ratio and increase the capacitance Is to provide.

  The object is achieved by the following means.

  (1) In the alloy composition, the Ga content AGa (mass%) of the layer containing 0.0005 mass% or more of Ga up to a depth of 5 nm from the surface and the internal Ga content BGa (mass%) from the depth of 5 nm. An aluminum material for an electrolytic capacitor electrode having a ratio AGa / BGa of 3 or less, and a current density rapid increase potential (E) nobler than -770 mV vs SCE and less than -710 mV vs SCE.

  (2) In the alloy composition, the aluminum purity is 99.98 mass% or more, Zn is 0.0002 mass% or more, and the Zn content CZn (mass%) and the Ga content CGa (mass%) are 0.0056 ≦ 6 CGa + 7 CZn ≦ 2. The aluminum material for electrolytic capacitor electrodes as described in 1 above, which satisfies the relationship 0.0245.

  (3) Fe is contained in the range of 0.0008 mass% to 0.004 mass%, Si is contained in the range of 0.0008 mass% to 0.004 mass%, Cu is contained in the range of 0.001 mass% to 0.008 mass%, and Pb is contained in the range of 0.00003 mass% to 0.0002 mass%. 3. The aluminum material for electrolytic capacitor electrodes as described in 2 above.

  (4) Ti content CTi (mass%), Zr content CZr (mass%) and V content CV (mass%) satisfy the relationship 0.00035 ≦ CTi + CZr + CV ≦ 0.0015, and B content is 0.0002 mass% or less, The aluminum material for electrolytic capacitor electrodes according to claim 2 or 3, wherein impurities other than Fe, Si, Cu, Ga, Zn, Pb, Ti, Zr, and V are each 0.001 mass% or less.

  (5) The aluminum material for electrolytic capacitor electrodes as recited in any one of the aforementioned Items 2 to 4, wherein Zn is contained in an amount of 0.0002% by mass or more and less than 0.0007% by mass.

  (6) The aluminum material for electrolytic capacitor electrodes as recited in the aforementioned Item 5, further containing 0.0008 mass% or more of Ga.

  (7) The aluminum material for electrolytic capacitor electrodes as described in 5 above, further containing 0.001% by mass or more of Ga.

  (8) A method for producing an electrode material for an electrolytic capacitor, comprising a step of performing etching on the aluminum material described in any one of (1) to (7).

  (9) The method for producing an electrode material for electrolytic capacitors as described in 8 above, wherein at least a part of the etching is direct current electrolytic etching.

  (10) An anode material for an aluminum electrolytic capacitor produced by the production method according to item 8 or item 9.

  (11) An aluminum electrolytic capacitor characterized in that the aluminum electrode material produced by the production method according to item 8 or 9 is used as the electrode material.

  According to the invention described in the preceding item (1), in the alloy composition, the Ga content AGa (mass%) of the layer containing 0.0005% by mass or more of Ga and having a depth of 5 nm from the surface and the inner part from the depth of 5 nm. Deep etch pits because the ratio AGa / BGa to the Ga content BGa (mass%) is 3 or less, and the current density sudden increase potential (E) is more noble than -770mV vs SCE and less than -710mV vs SCE Can be generated with high density and uniformity, and the area expansion rate can be reliably increased and the capacitance can be increased. Moreover, since it contains 0.0005% by mass or more of Ga, it is possible to use a large amount of aluminum lump purified by the segregation method, which is cheaper than the three-layer electrolysis method, and to realize both high capacitance and low cost requirements. Can do.

  According to the invention described in the preceding item (2), in the alloy composition, the aluminum purity is 99.98% by mass or more, Zn is 0.0002% by mass or more, and the Zn content CZn (% by mass) and Ga content Since CGa (mass%) satisfies the relationship of 0.0056 ≦ 6CGa + 7CZn ≦ 0.0245, deeper and more uniform etch pits can be generated, and the capacitance can be further increased.

  According to the invention described in the preceding item (3), Fe is 0.0008% to 0.004% by mass, Si is 0.0008% to 0.004% by mass, Cu is 0.001% to 0.008% by mass, and Pb is 0.00003% by mass. % Or more and 0.0002 mass% or less, etch pits can be grown while suppressing uneven formation and local generation of etch pits, and the capacitance can be increased.

  According to the invention described in the preceding item (4), the Ti content CTi (mass%), the Zr content CZr (mass%) and the V content CV (mass%) satisfy the relationship 0.00035 ≦ CTi + CZr + CV ≦ 0.0015, And the B content is 0.0002% by mass or less, and impurities other than Fe, Si, Cu, Ga, Zn, Pb, Ti, Zr, and V are each 0.001% by mass or less. Therefore, it is possible to prevent the formation of concentrated concentrations and increase the capacitance.

  According to the invention described in the preceding item (5), Zn is contained in an amount of 0.0002% by mass or more and less than 0.0007% by mass, so that an excellent electrostatic capacity can be obtained.

  According to the invention described in item (6) above, since Ga is further contained in an amount of 0.0008% by mass or more, a further excellent electrostatic capacity can be obtained.

  According to the invention described in the preceding item (7), 0.001% by mass or more of Ga is further contained, so that a further excellent electrostatic capacity can be obtained.

  According to the invention according to item (8), an electrode material for an electrolytic capacitor having a large capacitance can be manufactured by etching.

  According to the invention of the preceding item (9), by performing at least a part of the etching by direct current etching, a large number of deep and thick tunnel-like pits can be generated, and the effect obtained by defining the composition of the aluminum material Can be efficiently exhibited.

  According to the invention which concerns on the preceding clause (10), it can be set as the anode material for aluminum electrolytic capacitors with a high electrostatic capacity.

  According to the invention of the previous item (11), an aluminum electrolytic capacitor having a high capacitance can be obtained.

  In the aluminum material for electrolytic capacitor electrodes according to the present invention, the reasons for limiting physical properties, the significance of adding each element, and the reasons for limiting the content are as follows.

  First, in the alloy composition of the aluminum material, Ga is contained at 0.0005 mass% or more, Ga content AGa (mass%) of the surface layer (layer having a depth of 5 nm from the surface), and Ga content BGa inside from the depth of 5 nm. The ratio AGa / BGa to (mass%) is 3 or less, and the current density rapid increase potential (E) is more noble than -770 mV vs SCE and lower than -710 mV vs SCE. Because of the reason.

  That is, Ga dissolves in the aluminum material and can contribute to the uniformity of etch pits in the first-stage etching, so it is necessary to contain 0.0005% by mass or more. If it is less than 0.0005% by mass, this effect is not sufficient, and it is disadvantageous in terms of purification cost. However, as the Ga content increases, the current density rapid increase potential (E) shifts in a noble direction. Therefore, if the Ga content AGa (mass%) of the surface layer is concentrated to a ratio AGa / BGa exceeding 3 with the internal Ga content BGa (mass%), the potential becomes too noble in the surface layer. Therefore, conversely, the generation of pits during the first stage etching is hindered and made non-uniform. Therefore, the ratio AGa / BGa between the Ga content AGa (mass%) of the surface layer and the internal Ga content BGa (mass%) needs to be 3 or less.

  In the case of Pb, which is well-known to promote the generation of etch pits in aluminum foil for electrolytic capacitors and to increase the surface area, the surface layer (layer up to 5 nm deep from the surface) is concentrated about 1000 times and expanded. Although the effect is exhibited, in the case of Ga, it does not concentrate on the surface layer, but dissolves in the inner aluminum so that it does not improve as much as Pb, but contributes to uniform pits.

  In addition, when performing purification using a segregation method, Ga has a particularly high equilibrium partition coefficient, so that purification efficiency is not good. From the economical viewpoint, the preferable Ga range is 0.0008% by mass or more, and the optimum range is 0.001% by mass or more.

  Further, regarding the current density rapid increase potential (E), if it is lower than -770 mV vs S.C.E, the solubility of the material itself is not improved, which is not preferable. When Ga is concentrated in the surface layer, it becomes diluted inside, and the current density rapid increase potential (E) shifts to the base. In order to control the ratio of the Ga content of the surface layer and the Ga content inside from the depth of 5 nm to 3 or less, the final annealing conditions have a great influence, and hold at a high temperature of 520 ° C. or more for 4 hours or more. There is a need. If the current density rapid increase potential (E) becomes nobler than -710 mV, it is not good because it prevents the generation of uniform pits. A preferred range of the current density rapid increase potential (E) is -765 mV to -740 mV.

  The aluminum purity is preferably 99.98% by mass or more, and if it is less than 99.98% by mass, the amount of impurities increases, and even if the content of a trace amount of added elements is controlled, over-dissolution tends to occur during etching and the etching characteristics are deteriorated.

  In the alloy composition, Zn is preferably contained in an amount of 0.0002% by mass or more. An attempt to suppress Zn to less than 0.0002% by mass is disadvantageous in terms of refining costs and is not economically effective.

  Zn is characterized by being concentrated in the surface layer about 5 times after final annealing and easily segregating at grain boundaries. Therefore, the optimum range of the Zn content is 0.0002% by mass or more and less than 0.0007% by mass.

  In addition to the above contents, Zn and Ga desirably have a Zn content CZn (mass%) and a Ga content CGa (mass%) satisfying the relationship of 0.0056 ≦ 6CGa + 7CZn ≦ 0.0245. Ga and Zn in the aluminum material are dissolved in the aluminum matrix, thereby increasing the solubility of the aluminum material during the second-stage etching, promoting the surface expansion effect of the etch pits, and increasing the capacitance. This effect is not sufficient when 6CGa + 7CZn is less than 0.0056. Further, if 6CGa + 7CZn is larger than 0.0245, it is not preferable because it causes over-dissolution. Preferably, the range is 0.0056 ≦ 6CGa + 7CZn ≦ 0.0210, and the optimum range is 0.0056 ≦ 6CGa + 7CZn ≦ 0.0189.

  In the chemical composition of the aluminum material, Si has an effect of preventing coarsening of crystal grains during recrystallization. If the content is less than 0.0008% by mass, the above effect is poor, and if it exceeds 0.004% by mass, the distribution of etch pits may be uneven. Furthermore, the upper limit with preferable Si content is 0.003 mass%.

  Fe is an element unavoidably contained in aluminum, and if it is contained in a large amount, depending on the final annealing temperature, Al-Fe-based precipitates may be formed, resulting in nonuniform etching pit formation. If the Fe content exceeds 0.004% by mass, it becomes easy to form Al-Fe-based precipitates, and it is disadvantageous in terms of refining costs to restrict it to less than 0.0008% by mass. Is good. Furthermore, the upper limit with preferable Fe content is 0.003 mass%.

  When Cu dissolves in the aluminum matrix, it increases the solubility of the aluminum material, promotes the growth of etch pits, and increases the capacitance. If the content is less than 0.001% by mass, the effect is poor, and if it exceeds 0.008% by mass, it may be over-dissolved and the etching characteristics may be impaired. Therefore, it is preferable to define the content in the range of 0.001 to 0.008% by mass. A preferred lower limit for the Cu content is 0.003% by mass, and a preferred upper limit is 0.007% by mass.

  Pb is concentrated on the surface of the aluminum material at the time of final annealing, uniformizing the generation of etch pits at the initial stage of etching, and suppressing the generation of local etch pits. If the amount is less than 0.00003% by mass, the above-described effect is poor. If the amount exceeds 0.0002% by mass, the aluminum surface is melted so much that the capacitance decreases. Therefore, the content is preferably in the range of 0.00003 to 0.0002% by mass. A preferable lower limit of the Pb content is 0.00004% by mass, and a preferable upper limit is 0.00015% by mass.

  Ti, Zr, and V preferably satisfy the relationship of Ti content CTi (mass%), Zr content CZr (mass%), and V content CV (mass%) of 0.00035 ≦ CTi + CZr + CV ≦ 0.0015. Peritectic elements such as Ti, Zr, and V are elements whose content increases when a refined lump using a segregation method is used. These elements tend to form an intermetallic compound with aluminum, and if contained in a total amount exceeding 0.0015% by mass, there is a possibility that the formation of etch pits may be non-uniform, and less than 0.00035% by mass. Since it is disadvantageous in terms of purification cost, it is not preferable. A preferable upper limit of the total content is 0.0011% by mass.

  Moreover, it is good to regulate B content to 0.0002 mass% or less. When B forms a compound with Ti, Zr, and V, etch pits may be locally concentrated, so it is preferable that B be as small as possible, and the content is restricted to 0.0002 mass% or less. The upper limit with preferable B content is 0.0001 mass%.

  Note that impurities other than Fe, Si, Cu, Ga, Zn, Pb, Ti, Zr, and V are each preferably 0.001% by mass or less. When each impurity is more than 0.001% by mass, the solubility of the aluminum material is increased and over-dissolution is not preferable.

  The method for producing an aluminum material for an electrolytic capacitor electrode according to the present invention comprises 0.0005% by mass or more of Ga, and the ratio of the Ga content of the layer up to 5 nm deep from the surface to the internal Ga content from 5 nm deep is The method is not particularly limited as long as it is a method capable of producing an aluminum material having a current density rapid increase potential (E) of no more than 3 and nobler than -770 mV vs SCE and less than -710 mV vs SCE.

For example, a continuous casting and rolling method in which a molten aluminum is continuously inserted between two cooling rolls to obtain a sheet-shaped ingot is effective. According to this method, since casting can be performed at a cooling rate of 1 × 10 ³ ° C./sec or more, segregation of Ga in the ingot is reduced as much as possible, and Ga can be uniformly distributed. . This facilitates uniform diffusion and distribution of Ga during final annealing, and segregation on the foil surface is less likely to occur. The thickness of the continuously cast rolled material is preferably 5 mm or more and 25 mm or less. If this ingot is thin, the degree of cold work is insufficient, and the cubic occupancy rate, which is important when direct-etching an aluminum material, becomes low. Cold rolling, intermediate annealing, and final annealing after continuous casting and rolling may be performed by ordinary methods. In some cases, it is possible to improve the cube orientation occupation ratio of the final aluminum material by performing homogenization and hot rolling after continuous casting and rolling.

  Further, it is desirable to purify the aluminum lump by an inexpensive segregation method. Even if many low-cost aluminum lumps refined by the segregation method are used more cheaply than aluminum lumps refined by the three-layer electrolysis method, deep etch pits are generated in high density and evenly, and the area expansion rate is surely increased. The capacitance can be increased, and both high capacitance and low cost can be achieved.

  Further, the thickness of the aluminum material is not limited. Those having a thickness of 200 μm or less, referred to as foil, and those having a thickness larger than that are also included in the present invention.

  The aluminum material according to the present invention is subjected to etching for improving the surface expansion ratio and used as an electrode material for electrolytic capacitors. Etching conditions are not particularly limited, but preferably a direct current etching method is employed. By the direct current etching method, the portion that becomes the nucleus of the etch pit promoted in the annealing is deeply and thickly etched to generate a large number of tunnel-like pits, thereby realizing a high capacitance.

  After the etching treatment, a chemical conversion treatment is preferably performed to obtain an anode material. In particular, it is preferably used as an electrolytic capacitor electrode material for medium pressure and high pressure, but it does not preclude use as a cathode material. Moreover, the electrolytic capacitor using this electrode material can realize a large capacitance.

  Next, specific examples of the present invention will be described.

  In manufacturing the foil, first, an aluminum alloy having the composition shown in Table 1 was continuously cast and rolled to form a strip having a thickness of 20 mm. These were homogenized under conditions of 600 ° C. × 5 hr, hot-rolled at a reduction rate of 75% from that temperature, and cooled immediately after rolling. Thereafter, it was rolled into a foil having a thickness of 100 μm through cold rolling and intermediate annealing, and after degreasing and cleaning, final annealing was performed under the conditions shown in Table 2 in an Ar atmosphere.

  For each of these foils, the ratio of the Ga content in the surface layer to the internal Ga content and the current density rapid increase potential (E) during polarization measurement were determined.

  The Ga content in a region (surface layer) from one side of the foil to a depth of 5 nm was measured by the following method.

First, a test piece of 50 cm ² of the test material was collected, and this test piece was immersed in a 0.02 mass% NaOH aqueous solution at 50 ° C. to dissolve the surface layer (5 nm depth from the surface). The solution was washed with an aqueous nitric acid solution, and the washing solution was mixed with the aqueous NaOH solution. The quantification of the dissolution thickness was based on the measured amount of dissolved Al by plasma emission spectroscopy. Further, the amount of Ga in the surface layer of the solution was measured by ICP-MS (inductively coupled plasma mass spectrometry). The internal Ga content was determined by first immersing the foil in a 1 mol / l HCl aqueous solution for 15 minutes, further immersing in a 1% by mass HF aqueous solution for 30 seconds, washing with ion-exchanged water and drying at 80 ° C. The amount of Ga was measured by glow discharge mass spectrometry. From the above measurement results, the ratio of the Ga content in the surface layer to the internal Ga content (Ga concentration ratio) was calculated. Table 2 shows the calculation results.

  The current density rapid increase potential (E) was measured by the following method.

First, the test material was immersed in a 5 mass% NaOH aqueous solution at 50 ° C. for 30 seconds, washed with water, immersed in a 30 mass% HNO ₃ aqueous solution for 60 seconds, and then washed with ion-exchanged water. Immediately after this treatment, N ₂ gas was blown in advance at 100 ml / min for 30 minutes or more, and the aluminum foil was immersed in a sufficiently degassed 40 ° C., 2.67 mass% AlCl ₃ aqueous solution and left for 5 minutes. After that, anodic polarization from a natural potential in a noble direction at a potential sweep rate of 20 mV / min gave a potential-current curve. At the time of measurement, platinum was used as the counter electrode, and a saturated calomel electrode (SCE) was used as the reference electrode. From this potential-current density curve, the current density rapid increase potential (E) was determined as follows.
1) Obtain a potential-current density curve (A) (FIG. 1).
2) In this potential-current density curve, the straight line (B) indicating the minimum change rate of current density (mA / cm ² ) in the range of potential -900mV vs SCE or more and -600 mV vs SCE or less, that is, the minimum change rate Draw a tangent at the indicated position.
3) In the potential-current density curve, the straight line (C) indicating the maximum rate of change of current density (mA / cm ² ) in the range of potential −900 mV vs SCE or higher and −600 mV vs SCE or lower, that is, the maximum rate of change. Draw a tangent at the position.
4) Let (P) be the intersection of (B) and (C), and let the potential (E) corresponding to (P) be the sudden increase in current density.
The measurement results of the current density rapid increase potential (E) thus obtained are shown in Table 2.

  Etching was performed by the following method.

After immersing in an aqueous solution containing HCl: 1 mol / l and H ₂ SO ₄ : 3.5 mol / l: 75 ° C., electrolytic treatment was performed at a current density of 0.2 A / cm ² . The aluminum material after the electrolytic treatment was further immersed in a hydrochloric acid-sulfuric acid mixed aqueous solution having the above composition at 90 ° C. for 600 seconds to obtain an etched aluminum material. The obtained aluminum material was subjected to chemical conversion treatment according to the EIAJ standard at a conversion voltage of 270 V to obtain an anode material, and the capacitance was measured. The results are shown in Table 2 together with relative comparison when the capacitance of Comparative Example No. 1 is 100.

  From the results in Table 2, the ratio of the Ga content in the surface layer to the internal Ga content, the current density rapid increase potential (E) during polarization measurement, and the composition of the aluminum material are within the scope of the present invention. No. 25 confirmed that the capacitance can be increased by etching as compared with Comparative Examples 1 and 2 that deviate from the scope of the present invention.

It is a figure which shows the electric potential-current density curve for calculating | requiring a current density rapid increase potential.

Claims (9)

In the alloy composition, Ga is contained 0.0005 mass% or more and 0.0027 mass% or less ,
Ti content CTi (mass%), Zr content CZr (mass%) and V content CV (mass%) satisfy the relationship 0.00035 ≦ CTi + CZr + CV ≦ 0.0015, and B content is 0.0002 mass% or less,
The balance consists of Al and inevitable impurities,
The ratio AGa / BGa between the Ga content AGa (mass%) of the layer up to 5 nm deep from the surface and the Ga content BGa (mass%) inside from the depth 5 nm is 3 or less, and the current density rapidly increases ( E) Aluminum material for electrolytic capacitor electrodes, which is more noble than -770mV vs SCE and less basic than -710mV vs SCE. In the alloy composition, aluminum purity is 99.98% by mass or more, Zn is 0.0002% by mass or more, and Zn content CZn (% by mass) and Ga content CGa (% by mass) are 0.0056 ≦ 6CGa + 7CZn ≦ 0.0245 Fe is contained in an amount of 0.0008 mass% to 0.004 mass%, Si is contained in an amount of 0.0008 mass% to 0.004 mass%, Cu is contained in an amount of 0.001 mass% to 0.008 mass%, and Pb is contained in an amount of 0.00003 mass% to 0.0002 mass%. The aluminum material for electrolytic capacitor electrodes according to claim 1. The aluminum material for electrolytic capacitor electrodes according to claim 2, containing Zn in an amount of 0.0002 mass% to less than 0.0007 mass%. The aluminum material for electrolytic capacitor electrodes according to claim 3, wherein the lower limit value of Ga is 0.0008 mass% or more. The aluminum material for electrolytic capacitor electrodes according to claim 3, wherein the lower limit value of Ga is 0.001 mass% or more. The manufacturing method of the electrode material for electrolytic capacitors characterized by including the process of etching in the aluminum material described in any one of Claims 1 thru | or 5. The method for producing an electrode material for an electrolytic capacitor according to claim 6, wherein at least a part of the etching is direct current electrolytic etching. An anode material for an aluminum electrolytic capacitor produced by the production method according to claim 6 or 7. An aluminum electrolytic capacitor characterized in that an aluminum electrode material produced by the production method according to claim 6 or 7 is used as an electrode material.

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