RESUMO
Objective To investigate the effects of titanium nitride(TiN) coating on corrosion resistance of dental Co-Cr alloy in the simulated oral environment. Methods The Co-Cr alloy commonly used was casted with specimen sized of 10 mm× 10 mm×3 mm. Then the specimen was coated with a thickness of 2.5 μm TiN coating on the surface by multi-arc physical vapor deposition. The Tafel polarization curves of the specimen before and after coating titanium nitride in artificial saliva were measured by electrochemical station. Results From the Tafel polarization curves, the specimen after coating TiN showed that both anodic polarization curve and cathodal polarization curve were fiat, natural corrosion potential moved to the positive way, and passivation interval got longer. From the annular anodic polarization curves, the specimen after coating TiN had almost no "delay area". Conclusion TiN coating can improve corrosion resistance of Co-Cr alloy.
RESUMO
Objective To study the effect of Mutans Streptococcus(S.Mutans) on the corrosion resistance of Ni-Cr alloy. Methods S.Mutans were isolated in TSB,and then 10~(5)10~6 CFU/mL of bacterial population was reached.The self-corrosion electrical current density and the corrosion electrical current potential of Ni-Cr alloy were found from polarization curves under the condition with or without media plus S.Mutans.The surface of Ni-Cr alloy after bacterial corrosion was examined with X-ray photoelectron spectroscopy(XPS) to find out different element contents.(Results)From polarization curves,it could be found that the self-corrosion electrical current density and the corrosion electrical current potential of Ni-Cr alloy without S.Mutans were 53.5 ?A/cm~(2)and-62 mV,and those with S.Mutans were 75.7 ?A/cm~(2)and-220 mV.Examination of XPS showed that besides Ni and Cr,the element of chlorine(Cl),sulphur(S),calcium(Ca) could be found on the surface of Ni-Cr alloy after bacterial corrosion.(Conclusion Because of) the metabolism of S.Mutans,an oxide film could be destroyed and a biofilm be formed on the surface of Ni-Cr alloy.Bacterial corrosion could lower the corrosion resistance performance of Ni-Cr alloy.