GB979968A - Method and apparatus for electrolytically working metals and quasi-metals by anodic decomposition - Google Patents

Abstract

<PICT:0979968/C6-C7/1> An electrolytic cell B, for forming a blind hole, depression, bore or grove in a workpiece M connected as anode, comprises an electrolyte container in communication at its lower end with a capillary tube, the lower end of which forms a tool head for engaging the workpiece, a cathode C being immersed in electrolyte in the container and the immersed volume of the cathode being large compared with the volume of the capillary tube. The cell is closely and tightly applied to the body M and the workpiece is movable relatively to the nozzle in three dimensions, e.g., axially of the nozzle to form a bore or laterally to engrave. The cell may be of silica or glass or its surface contacting the workpiece may be coated with an electrically insulating and corrosion proof film, e.g. of a baked silicone oil. The cathode may be a Pt wire coil. The inner diameter of the capillary tube may be as small as 0.2m . There is a non-linear relation between voltage and current and there is an optimum voltage for working at which oxygen bubbles are evolved which usefully agitate the electrolyte. Specified metals and quasi-metals which may be worked and the electrolytes to be used are: Cu, Ni and Mo-orthophosphoric or chromic acid; Co-HNO3 or H2SO4; W or tungsten carbide-NaOH. In an example, a hole of diameter 24m and depth 16m was drilled in a W plate in 35 seconds at a working efficiency of 40% using a voltage of 22 and current of 31m A.