高純度アルミニウム箔の塩酸溶液中における交流エッチングで生ずる生成物と拡面倍率

Abstract

During AC etching of aluminum foil used in electrodes for electrolytic capacitors, an anodic oxide film and a non-uniform aluminum hydroxide develop over the etched cell surface. The effects of these products on enlargement of surface area were investigated in 3.6wt% hydrochloric acid solution at 303K by applying AC with an asymmetrical triangular wave and a compound waveform of anodic current with a triangular wave and cathodic current with a square wave. The amount of aluminum hydroxide was measured using a stripping method and the thickness of the deposition layer was calculated assuming that the product is present homogeneously on the entire etched cells surface. Marked enhancement of specific surface area was obtained under condition where the deposition rate of the aluminum hydroxide at the half cycle of cathodic current was high and the pit nucleation potential at the half cycle of anodic current was maintained at about -0.2V (vs. SCE). Larger pits appear at a more noble potential and dissolution takes place on entire aluminum surface as a whole at a less noble potential. The breakdown behavior of anodic oxide film is affected by the cycle of cathodic current to controll the rate at which chloride ions are supplied to the etched cell surface.