INVENTION OF CYCLIC RESISTOMETRY

A new technique is described that can measure the time-varying resistance of an electrode during cyclic voltammetry. We call it 'cyclic resistometry'. It is based on the principle of measuring the resistance with square galvanostatic pulses, which are so fast that Faradaic reactions and double-layer charging do not respond to them. The pulses are fired very briefly - in less than 200 mu s - during which time the potentiostat is switched to a dummy cell and the working electrode is controlled by a potentiostatic/galvanostatic mode switching. A sample-and-hold circuit then provides an analog output of resistance that is updated every 33 ms. The utility of the technique is demonstrated on three systems of industrial importance; the anodic dissolution of iron and copper from mineral chalcopyrite, the corrosion of lead electrodes in sulfuric acid and the redox cycling of electrochromic films of iridium oxide.