Corrosion stability of metallic materials used in dentistry is a major concern; identification of materials combining high stability and good performance is needed. The corrosion resistance of representative nonprecious metal alloys frequently used in dentistry in contact with artificial saliva solution with various added substances encountered in foodstuffs and in materials used in dentistry, possibly influencing the corrosion has been studied in vitro with electrochemical impedance measurements. Values of obtained corrosion resistances are interpreted in terms of conceivable effects of the additives on the rate of corrosion; they are also compared with previous results obtained with these alloys and additives using breakthrough electrode potentials obtained from slow scan cyclic voltammetry reported before.