The aim of this study has been to find out the effects of pH degrees of oral environment on the corrosion of dental metals and alloys which have different composition by electrochemical methods. The surface structure of the first and second casting of dental metals and alloys were examined under the Scanning Electrone Microscope. Their composition were investigated by the Energy Dispersive X-Ray Analysor system. The rotary disc electrode was prepared by these materials. The potential changes of these electrodes by time were established in three different pH solutions, and their current-potential curves were obtained by the potentiodynamic method. In addition the changes of corrosion potentials due to time was also determined.