Cardiac pacemakers and cochlear implants are examples for medical devices that make use of active electrodes from platinum, iridium or their alloys. They require relatively high voltages to stimulate body functions such as muscle contraction or nerve stimulation. From an electrochemical point of view the electrochemical window of the water based body fluids is exceeded and thus water splitting can occur. However, there is an important side reaction which has not been proven so far, that is the electrochemical dissolution of the noble metal electrodes. From a financial point of view these losses could be easily accepted in relation to other costs such as the required surgery or the hospital stay. The important point is that the minor dissolution is under suspect of being responsible for the nerve degeneration that leads to a malfunction of these devices. In an attempt to clarify the mechanism combined experiments were performed in which electrochemical impedance spectroscopy at certain bias potentials was performed and the resulting noble metal dissolution was quantitatively monitored by an extremely sensitive analytical method the so called inductively coupled plasm mass spectroscopy (ICP-MS). For a simulation of the in operando conditions large amplitude frequency measurements were performed to understand the relationship between dissolution rate and frequency.
