Abstract: An aluminum material for electrolytic capacitor electrodes, the aluminum material having aluminum purity of 99.9% or more, consisting of: Si: 2 to 50 ppm; Fe; 2 to 50 ppm; Cu: 15 to 150 ppm; Zn: 1 to 80 ppm; Pb: 0.1 to 3 ppm; at least one of Zr and V: 11 ppm or more, a total content of the at least one of Zr and V being 11 to 100 ppm; and the balance being Al and impurities, wherein a content of B is controlled to be 2 ppm or less. In the aluminum material, Ti: 1 to 30 ppm, Mn group composition (at least one of Mn, Ga, Mg and Ca): 1 to 50 ppm in total, and In group composition (at least one of In, Sn, Sb): 1 to 30 ppm in total are selectively added. A method for manufacturing an aluminum foil for electrolytic capacitor electrodes according to the present invention, comprises the steps of: rolling the aforementioned aluminum material into a foil; and performing final annealing of the foil at the temperature of 430 to 580° C.

Abstract: An aluminum electrode foil for an electrolytic capacitor has a sponge-like etching layer formed on at least one of the surfaces thereof, and the sponge-like etching layer is reduced in a direction of thickness. The aluminum density of the reduced sponge-like etching layer `d2` is set from 0.8 to 2.2 g/cm.sup.3.

Abstract: A raw aluminum foil for use to prepare electrolytic condenser electrodes has an aluminum purity of 99.9% or higher and contains 50-500 ppm of Mg. A method of etching the raw foil to prepare the electrodes consists of a primary etching step and a secondary etching step, and the primary etching is conducted in an aqueous bath containing 3-10% by weight of HCl and 10-40% by weight of H.sub.2 SO.sub.4, at 70.degree.-90.degree. C. and with a current density of 10-40 A/dm.sup.2. The secondary etching is conducted electrolytically or chemically in a further bath containing 3-10% by weight of HCl, with or without 1% or less of H.sub.2 C.sub.2 O.sub.4 added to the further bath, at a bath temperature of 70.degree.-95.degree. C. and with a current density of 0-10 A/dm.sup.2.

Abstract: An aluminum foil to be etched for use as the electrolytic condenser electrodes is composed of a foil body of an aluminum purity of 99.9% or higher, and an oxide layer 20-70 .ANG. thick and formed due to contact of the foil body with an oxidizing atmosphere. At least one etching nuclei-forming element is concentrated in a boundary region and/or in an outermost surface region of the oxide layer, the boundary region being disposed between the foil body and the oxide layer, and both the regions having a thickness of 20 .ANG. or less. The ratio in ion intensity of a maximum concentration of the elements in these regions to a concentration of the elements in the inner layer of the foil body is 1.2-30. There are three patterns in distribution of the elements, so that the maximum concentration is in a predetermined ratio to the concentration in the surface region, the inner layer or a minimum concentration appearing between the regions.

Abstract: Aluminum foils used as a material of electrodes in electrolytic capacitors are manufactured by a method which comprises a step of forming at first an initial internal oxide coating 5 to 50 .ANG. thick on the surface of the aluminum foils before they are electrochemically or chemically etched later. The aluminum foils are then subjected to high temperature heat treatment such that the whole thickness of the oxide coating does not exceed 70 .ANG..

Abstract: A process for treating the surface of aluminum foil for use as an electrode of electrolytic capacitors to increase the surface area of the foil to the greatest possible extent includes the three steps of pre-etching treatment, intermediate nitric acid treatment and post-etching treatment. The pre-etching treatment is conducted electrolytically in an aqueous solution of chromic acid and at least one of chromic acid and chromates. The intermediate nitric acid treatment is carried out by immersing the pre-etched foil in an aqueous solution of nitric acid to remove a chromate film formed by the pre-etching from the foil surface, especially from the interior of the resulting pits. The post-etching treatment is conducted electrolytically in an aqueous solution of hydrochloric acid, or hydrochloric acid and an oxidizing acid.