Surface examination of electrodes of removed implants

The influence of the corrosive environment in human tissue on implantable platinum electrodes during long term electrical stimulation with monophasic voltage stimulation pulses was studied. Various anomalies caused by electrochemical reactions and/or mechanical deformations produced on the surface of the electrodes owing to electrical stimulation were identified and investigated by means of scanning electron microscopy. Since the corrosion reactions of the electrodes depend mostly on the composition of the electrode-electrolyte system, the potentials of anode and cathode during pulsing were measured in 0.9% NaCl solution and in vivo.