Zonal coulometric analysis of the corrosion resistance of dental alloys

Objectives: The corrosion resistance of a series of 51 dental alloys and pure metals was evaluated by coulometric analysis. Methods: The method consisted of dividing the anodic polarization curves into three separate zones; zone I, from the open-circuit potential (after 24 h immersion) up to + 300 mV (SCE); zone II, from 300 mV to 700 mV (SCE); zone III, + 700 mV to 1000 mV (SCE). The surfaces below the curves are integrated for each zone and the results expressed in millicoulombs (mC). Results and conclusions: Although the intensity of degradation in the mouth may vary from patient to patient, we think that a potential danger may occur in zones I and II in particular. Coulometric analysis reveals that: (i) the alloys for the porcelain-fused-to metal (PFM) technique have a better corrosion resistance (2.58 mC on average for the sum of the three zones, against 283.7 mC for conventional alloys); (ii) the elements Cu, Ag and Ni reduce the corrosion resistance of gold-based alloys; (iii) within the same class, single-phase alloys resist better than two-phase alloys.