IMPROVED PROCESS FOR ELECTROLYTIC ETCHING OF ALUMINIUM FOIL FOR USE AS ANODE IN THE FABRICATION OF HIGH VOLTAGE ALUMINIUM ELECTROLYTIC CAPACITORS

摘要

Improved process for electrolytic etching of aluminium foil for use as anode in the fabrication of high voltage aluminium electrolytic capacitors, wherein plain aluminium foil is subjected to a two stage etching process, characterized in that the first stage etching is carried out 8in an aqueous solution containing (i) a soluble alkali or alkaline earch metal chloride in the concentration range of between 2 and 15% and (ii) borie acid in the concentration range of between 5 and 20% followed by a second stage etching in an aqueous solution containing (i) a soluble alkali metal nitrate in concentration range of between 5 and 20% and (ii) soluble alkali metal chloride, sulphate or acid phosphate in the concentration range of 0.1 to 2% using direct current from a three phase rectifier and watching the etched foil free of chloride ions. (Prov. Specn. 7 Pages. Comp. Specn. 10 Pages. Drgs. Nil.)