Electrochemical characterization of cobalt-based alloys using the mini-cell system.

Objectives: The aim of this work was to investigate the electrochemical behavior of cobalt-based alloys of different compositions using the mini-cell system (MCS) and to test the sensitivity of this technique in the detection of variations in the electrochemical behavior caused by the different compositions of cobalt-based alloys.

Methods: The electrochemical measurements were performed on two cobalt-based alloys, having a small content of gold (Bärlight and Gold Core); one cobalt-platinum-ruthenium alloy (Porta Smart) and one classical Co-based alloy (Wironit), in two different electrolytes, 1% NaCl and phosphate buffered solution (PBS).

Results: Based on I versus E curves, enhanced pitting corrosion capability was observed for the cobalt-based alloys, especially for those with lower chromium content and with the addition of a small amount of gold. The alloying of Co with Pt and Ru (Porta Smart), and the standard Co-based alloy do not show any critical instability; in contrast, a small addition of Au enhanced the pitting corrosion activity and reduced the corrosion stability. For higher alloy stability, a minimum 30% atomic ratio of chromium in the alloy composition is necessary. Furthermore, it was shown that MCS has sensitivity for the qualitative comparison of the alloys as well as in the electrochemical characterization of each alloy.

Significance: Electrochemical measurements are essential to assess the quality of an alloy. MCS might help in understanding the role the elements play in the electrochemical behavior of the alloys and at the same time contribute to the selection of the alloys in terms of their quality, even before more complex tests in vitro or in vivo are applied, and might reduce the costs for materials research.