A comparative investigation of the formation, stability, and dissolution oi copper and silver clusters on polycrystalline gold electrodes with in-situ STM was conducted in order to access three closely related problems in parallel. The first topic is the dynamic behaviour of metal clusters in electrochemical environments. The second is the relation between macroscopic kinetic parameters and the structural dynamics on the nm-scale. These two topics are directly connected to the question, whether and how the STM tip affects the local electrochemical kinetics.