Preferential dissolution behaviour in Ni-Cr dental cast alloy

A Ni-Cr-Mo dental alloy was fabricated by three different casting methods, viz. centrifugal casting, high frequency induction casting and vacuum pressure casting. The dependence of cast microstructure on the electrochemical corrosion behaviour was investigated using potentiodynamic cyclic and potentiostatic polarization techniques, impedance spectroscopy and scanning electron microscopy. The experimental results were compared and discussed with those obtained for a Co-Cr-Mo counterpart. The results of the study showed that the variation in casting morphologies with casting methods has only marginal influence in the overall corrosion resistance of Ni-Cr and Co-Cr dental alloys. There was severe preferential dissolution of Ni rich, Cr and Mo depleted zones from the Ni-Cr-Mo alloy. The overall corrosion resistance property of the Co-Cr base alloy was better than that of the Ni-Cr base alloy.