The aim of the studies was to investigate corrosion processes and surface effects on 6 dental alloys in dependence on organic electrolyte components. For this reason in vitro experiments were carried out in a laboratory bioreactor as follows: 1. Potentiodynamic polarization measurements on dental alloys in different organic electrolytes (microbial culture medium called DNB with and without Streptococcus mutans OMZ 176) under defined test conditions (standard test).2. Potentiodynamic polarization measurments (equal conditions) on precious dental alloys in DNB with and without bacteria in different times after measuring start (0, 6, 12, 24, 48, 72 h) (long-term test).3. Galvanostatic polarization measurement (i=10 µA, t=2h 47min) in an anorganic multicomponent electrolyte according CEN 30993 with and without albumin (1% bovine serum albumin) and determination of the metal release by means of AAS. The results obtained in the organic electrolytes demonstrate that the current density-potential-curves are moved to higher potentials in comparison to measuring in inorganic electrolytes. The long-term tests show also a moving of the curves to higher potentials after a time of 72 hours. The current density decreases in the same time. This phenomen is caused by formation of biofilms.Further an addition of albumin causes an increase of galvanostatic pitting potential, what refers to a formation of biofilms. This is opposed to the amount of released ions determined in the electrolyte with albumin. The corrosion behaviour is mainly influenced by the quality of the electrolyte, especially of organic components. Therefore in vitro-corrosion tests of metallic biomaterials should be carried out under simulated biological conditions. Keywords: dental alloy, corrosion, biocompatibility, organic electrolytes, ion release