Galvanic corrosion of two non noble dental alloys

This study aims to evaluate the corrosion resistance of two non-noble dental alloys, namely, the Wiron®88 (Ni-Cr-Mo) and the Remanium 2000+ (Co-Cr-Mo-W). A noble alloy, the V-Gnathos^® Plus (Au-Pt) previously studied was also considered for the purpose of comparison. The study was conducted in artificial saliva, pH 7.1, at 37 °C, by cyclic and linear sweep voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The R_p value of the alloy of high contents of Ni, the Wiron^®88, was 26.2±0.2 kΩ cm² and of the one with high contents of Co, the Remanium 2000+, was 22.5±0.6 kΩ cm². Data from linear polarization resistance and electrochemical impedance spectroscopy lead to the same order for the resistance against corrosion. The order from the less to the more reactive alloy is: Wiron^®88 → Remanium 2000+. The galvanic cell obtained by coupling the two non?noble alloys presents very low cell potential (a few mV, -18 mV), while the galvanic cell between one noble alloy (the V-Gnathos^® Plus) and the Wiron®88 showed a higher cell potential (-104 mV). Both galvanic couples, under short circuit, have lead to the release of cations, namely, Co²⁺, in the case of the Wiron^®88|Remanium 2000+ and Ni²⁺ for the Wiron^®88|V-Gnathos^® Plus, galvanic couples, respectively, with the ionic concentrations reaching values of 12.15 and 7.30 μg L^-1 (7.30 ppb), respectively. SEM micrographs obtained after 25 days immersion in artificial saliva, at 37 °C, showed the formation of well-defined pits on the surface of the two non-noble alloys.