Cobalt-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.
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