Abstract
The objective of this investigation was to study the compositional influence on the corrosion behavior of Ni-Cr-Mo dental casting alloys in acidic artificial saliva. Cyclic potentiodynamic and potentiostatic tests were used to evaluate the corrosion behavior of different Ni-Cr-Mo dental casting alloys in deaerated artificial saliva with pH 5 at 37℃.Optical microscope observations were carried out after the cyclic potentiodynamic tests. Surface chemical analyses were characterized by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) after potentiostatic tests. The results of corrosion tests showed that the corrosion resistance of Ni-Cr-Mo casting alloys was associated with the formation of passive film, containing Ni(OH)2,NiO,Cr2O3 and MoO3,on the surface. The Ni-Cr-Mo alloy with higher Cr(≈21%)and Mo(≈8%)contents had much larger passive region in the polarization curve and was immune to pitting corrosion, which was due to the presence of high Cr(maximum≈31-35%)and Mo(maximum≈12%)contents in the surface passive film. The presence of Ti lower than 4% in the Ni-Cr-Mo casting alloy had no effect on the corrosion resistance. A pitting resistance equivalent (PRE) of about 49 could provide the Ni-Cr-Mo alloy with a good pitting corrosion resistance.
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