Corrosion of ferromagnetic alloys used for magnetic retention of overdentures.

Three ferromagnetic casting alloys intended for use with magnetically retained overdentures (compositions in wt%: #1, Pd 50, Co 47, Ga 2, Pt 1; #2, Pd 60, Co 37, Ga 2, Pt 2; #3, Pd 49, Co 46, Ga 2, Pt 2) were investigated. A 0.9% saline solution and an artificial saliva (Meyer) were used for evaluation of the electrochemical corrosion behavior of these alloys, utilizing standard potentiodynamic techniques. All alloys investigated possessed a good corrosion resistance in the potential range of the oral environment (from -100 to 300 mV versus SCE). In addition, alloys #1 and 3 appeared to be susceptible to pitting above +300 mV (SCE), while #2 was resistant to pitting and was found to passivate in 0.9% saline solution.