Hull Cell Investigations of Electrostructuring and Electropolishing

Spring 1997

Prof Dr.-lng. Andreas Visser, Dipl.-Ing.

As we started the investigation of the electro­chemical removal processes Electrostructuring and Electropolishing there was the need to find a sim­plistic method to examine many different electro­lytes and several combinations of materials and solutions. Since the Hull Cell has been used to ex­amine electrodeposition processes very success­fully [1}, we had the idea to use it for the investigation of our electroremoval processes. In the past, the Hull Cell has been applied to electropolishing (1,2], but it had never been used to examine the electrostructuring process systemati­cally. Electrostructuring was developed out of the electropolishing process (3). In both cases surface areas of an anodic metal workpiece are removed under help of a specific electrolyte. As a high disso­lution rate and an optimal surface quality with mir­ror finish is wanted, both removal processes are established in the transpassive zone of the current density voltage curve. In case of brass dissolution the reactions shown in picture 1 take place. Copper and zinc dissolve as bivalent ions. In the transpassive zone oxygen is developed at the anode and hydrogen is generated at the cathode. Besides the more noble copper deposits at the cathode. Ar­eas, which should not be removed, were covered with special screen printing lacquer, varnish, adhe­sive tape or photoresist. In this way embossed structures are produced.