Electrochemical and surface studies on the passivity of a dental Pd-based casting alloy in alkaline sulphide solution

Abstract The corrosion and tarnish behavior of a dental casting Pd–25Ag–18Cu–12Au alloy in 0.1% Na2S solution at 37 °C was investigated using potentiodynamic polarization and spectrocolorimetric techniques. The surface film was characterized by X-ray photoelectron spectroscopy (XPS). This alloy exhibited markedly higher resistance to corrosion and tarnish than did the Ag–20Pd–18Cu–12Au alloy in current clinical use. XPS spectra indicated the presence of a thin sulphide film composed of PdS. It was found that the PdS film is very protective and is responsible for the passivity of the Pd–25Ag–18Cu–12Au alloy in 0.1% Na2S solution.