INVESTIGATIONS INTO THE ACTIVE PASSIVE TRANSITION OF 304 STAINLESS-STEEL IN ORGANIC MEDIA CONTAINING WATER AND HYDROGEN-CHLORIDE PART 1. IR DROP MEASUREMENT BY A COMPUTER-ASSISTED INTERRUPTER TECHNIQUE

An interrupter technique with computer-assisted calculation of the ohmic potential drop UΩ is described. It allows to measure UΩ while the working electrode is under potentiostatic control. As an additional result the differential double layer capacity CD is calculated, which includes some informations about the state of the working electrode surface. Experiments with the presented interrupter technique show, that just using a Luggin capillary is absolutely insufficient to avoid IR drop, especially in low conductive media: steady state current-potential curves will yield erroneous results of the kinetic parameters of the electrode reactions if the IR drop is not carefully eliminated. The described interrupter technique gives the same results for the ohmic resistance RΩ as eg AC techniques or potential pulse measurements. The value of RΩ measured is always associated with the primary current distribution.