Passivity of Co-Cr-Mo alloys in lactic acid solutions

Abstract

The method of potentiodynamic polarization was used to obtain the electrochemical measurements of ten experimental Co-Cr-Mo alloys with different chemical composition in two solutions of 0.1 % lactic acid (LA): medium A containing Cl − -ions (0.1 % LA in artificial saliva, pH 6.52) and medium B without Cl − -ions (0.1 % LA in distilled water, pH 2.99). These solutions as representative of oral cavity conditions were chosen in order to see if the alloys could be used in dental practice. Wironit was used as reference material.In vitro experiments have shown that susceptibility to local corrosion was more pronounced in solution A. In contrast, the tendency to general corrosion was greater in solution B.Referring to pitting potential of Wironit , samples 3 (Co55CR40Mo5), 6 (Co60CR30Mo10) and 9 (Co55CR20Mo25) have shown the best performances with the highest Epitt value in both media. The same is valid for these three alloys if general corrosion was considered.K e y w o r d s : Co-Cr-Mo dental alloys, passivity, lactic acid, artificial saliva, corrosion properties