Influence of the Cr Content on the Corrosion Properties of a Series of Binary Cobalt-Chromium Alloys in Acidic Artificial Saliva

International audienceCobalt-based alloys are more and more considered for dental applications, instead the expensive noble alloys and the other predominantly based alloys based on the allergen element nickel. These alloys frequently contain chromium to allow good resistance against corrosion as this may take place in the buccal milieu. The most often chromium is present in high quantity, close to 30wt. %, but it is maybe possible to decrease a little its contents without losing corrosion resistance. The aim of this study is exploring how the corrosion behavior of a cobalt alloy may vary versus its chromium content. In order to simplify this investigation only Co-xCrbinary alloys were considered, with x decreasing from 30 to 0wt.% by slices of 5wt.%. A series of seven alloys was synthesized by foundry under inert atmosphere and their behavior in corrosion in an artificial saliva of simple composition (NaCl 9g/L) acidified to pH=2.3 was specified using various classical electrochemical techniques (open circuit potential follow-up, Stern-Geary, Tafel, cyclic polarization). It appeared that passivation of the alloys occurred during the first two hours of immersion when the chromium content was 10 wt. % or higher, with as result high corrosion potentials and low corrosion current densities