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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.

The influence of mucin on the corrosion behaviour of seven typical dental casting alloys was investigated. A commercial saliva substitute (Saliva Orthana) containing mucin, and a control from which the mucin had been removed, were used. The electrochemical behaviour of the test alloys was evaluated around the open circuit potential (OCP) utilizing standard potentiodynamic techniques, as a function of oxygen concentrations and pH. The results of the corrosion measurements were analysed by a four-way ANOVA to detect the influence of alloy, environment and possible interactions. Mucin seems to act as a cathodic inhibitor at pH 6.7 but not at pH 4.6. An unidentified component (e.g. benzoate) of the saliva substitute probably acts as an adsorption inhibitor. Anodic passivation is also correlated with the artificial saliva composition.