Electrochemical determination of the corrosion resistance of NiCr dental casting alloys

Abstract

Based on the polarization curves and electrochemical impedance spectroscopy (EIS) in the case of four commercial dental alloys (Wirolloy, Heraenium, NicromalSoft and VeraSoft) maintained in 0.1 M NaCl solution, it was established the type and the intensity of the corrosion process by means of the corrosion currents value. The passivation of all the samples occurred spontaneously at the open circuit potential. The corrosion currents value decrease after the alloys maintenance in the corrosive medium due their passivation. The corrosion currents have values of nA order for all the samples and decrease with the increase of the immersion time. The alloys Heraenium and Wirolloy are in the optimum corrosion resistant condition. The VeraSoft and NicromalSoft alloys presented a dangerous breakdown potential (about 200–300 mV). The EIS results show that all NiCr-based alloys exhibits passivity at open circuit potential. The Heraenium and Wirolloy alloys with dendritic microstructure show the best electrochemical behaviour in 0.1 M NaCl solutions