Effect of pH on Electrochemical Behaviour of a Ni-Cr-Mo Commercial Dental Alloy in Chloride Medium

摘要

Basic metal alloys, as Ni-Cr-Mo, have been widely used in the manufacture of fixed and removable prostheses, due to their desirable physical and mechanical properties. However, these alloys undergo an oxidation in the oral environment, which causes metal ions release in the body, leading to harmful systemic effects for human health. The purpose of this study is to assess the electrochemical behavior of a Ni-Cr-Mo commercial dental alloy, in a physiological environment that simulates the aggressiveness of oral cavity (0.9% NaCl solution) with its pH varying from 2.0 to 6.0. The corrosion behavior was assessed by electrochemical measurements which are commonly applied in metals’ corrosion study, with quantitative parameters to estimate corrosion resistance. In the open circuit potential curves, it was observed a typical behavior of passive state, mainly at pH 4.0 and 6.0. On the potentiodynamic curves it was observed that the passive current density increased and the re-passivation potential decreased with diminishing pH, suggesting that the re-passivation does not occur at pH 2.0. Chronoamperometric curves, as well as EIS spectra shapes, were consistent with these analyses. The results obtained from different methods of analyses indicate that corrosion resistance can be affected by pH changes in a saline medium.