Electrochemical characterization of some cobalt base alloys in Ringer solution

Highlights: • The behavior of two Co–Cr dental alloys in Ringer solution was investigated. • Both alloys tend to passivate and this passivation tendency is very high. • The alloys present the formation of a mixed protective layer Cr₂O₃·CoO. • The high stability of passive film substantially improves their biocompatibility. Biomaterials should be thoroughly studied in order to make sure they do not cause any harm to the human body. Considering that biocompatibility is very strict, the material must be non-toxic, and not cause any allergies or inflammation in the body. Of the different categories of metallic biomaterials, the cobalt-based alloys are among the preferred options. Applications can be found in orthopedic implants, and both cardiac and dental fields. Co–Cr alloys have been used in dentistry for porcelain-fused-to-metal (PFM) crowns due to their biocompatibility, wear resistance, long service duration, good mechanical properties, and last but not least, superior resistance to corrosion. The present investigation evaluated and compared two Co–Cr based dental alloys, studying their microstructural characterization and corrosion behavior in Ringer solution, using various techniques. Findings in this investigation revealed a high passivation tendency for the two alloys studied, with the formation of mixed protective layers Cr₂O₃·CoO with high stability on their surfaces, which substantially improves their biocompatibility in Ringer solution. The kinetic parameters of the corrosion process in the experiment indicated a two-time constants process with an anodic control, attributable to the formation of passive films on their surfaces. According to the results obtained in this investigation, the polarization resistance of the two Co–Cr alloys examined in Ringer solution reached the values of biomaterials with a high resistance to corrosion, and the passive films formed on their surface had a more than appropriate resistance to corrosion.