Corrosion of NiCr Alloys for Dental Applications: Effects of Environment, Chemical Composition and Casting Route

The aim of this work is the assessment of the corrosion resistance of NiCr-based casting alloys in oral environments. The variables considered were the chemical composition of the source (raw) material, the casting process used and the characteristics of the environment. The following materials were tested: NiCr V (Ni 70-77 , Cr 11-14 , Mo 3.5-8 wt.%), NiCr W (Ni 59.6 , Cr 24 , Mo 9.8 ) and NiCrTi (Ni 60-76 , Cr 12-21 , Mo 4-14 , Ti 4-6 ). Corrosion resistance was investigated by using electrochemical methods, and the corrosion morphology was determined by surface analysis techniques (SEM and optical stereoscopy). Results showed that the chemical composition of the source material was the determining factor for corrosion resistance, while the casting route and environment modification with fluoride addition did not affect the corrosion behavior of NiCr alloys. The corrosion morphology was localized exhibiting a peculiar dissolution pattern as observed in scanning droplet cell microscopy analysis. Furthermore, it was concluded that titanium segregation in the alloy after casting process was responsible for the lower localized corrosion resistance observed.