Nanoscale evaluation of the dynamic interface and corrosion resistance of the chemically generated oxide film on dental vitallium alloy in simulated physiological solution

Various biomaterials including Vitallium alloys are frequently utilized in medical applications, in particular as dental materials. A fundamental prerequisite for their application is their biocompatibility, mechanical stability , and corrosion resistance in the oral cavity. Herein, the corrosion resistance of a ternary CoCrMo alloy , namely Vitallium, was investigated in a simulated physiological medium, 0.9 % NaCl saline solution , at body temperature over various immersion times. The corrosion behavior and surface passivation were evaluated using open circuit measurement, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), Mott–Schottky analysis along with X-ray diffraction (XRD), scanning electron (SEM) and atomic force (AFM) microscopy. To assess the stability of the created passive film, the study was performed over 7 days of immersion in the saline solution. The electrochemical polarization tests revealed a decrease in the corrosion current along with an increase in the corrosion resistance after 168 h. Furthermore, EIS showed an improvement in the protective properties of the passive film with prolonged exposure. This was confirmed by ICP-AES analysis. Additionally, this chemically generated passive film exhibited n-p type semiconductor characteristics, with increasing thickness and fewer defects over the immersion time, making it more protective. XRD analysis revealed only a γ-phase with a face-centered cubic structure. Importantly, the microstructure and roughness parameters of the alloy surface were evaluated with prolonged exposure to the corrosive medium at the nanoscale using SEM-EDX and AFM . Results elucidated that the origin of the corrosion resistance of Vitallium stems mainly from the formation of a passive layer.