Comparative study of film formation on high-purity Co and Stellite-6: Probing the roles of a chromium oxide layer and gamma-radiation

Gamma-irradiation significantly increases the corrosion potential on pure Co and the cobalt alloy, Stellite-6. To understand the radiation-induced corrosion of these materials, electrochemical studies of film formation and conversion on these metals were performed as a function of potential under both potentiodynamic and potentiostatic conditions. The oxidized surfaces were characterized by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Four characteristic potential regions are identified for anodic oxidation. Comparison of the behavior of pure cobalt and a cobalt alloy provides an insight into the role of an initial air-formed chromium oxide layer on the oxidation of Stellite-6 under different corrosion conditions.

► Comprehensive study comparing anodic film formation on Co and Stellite-6.
► Study shows gamma-irradiation increases the corrosion potentials on these materials.
► Anodic film formation studied using a range of electrochemical and surface analyses.
► Anodic oxidation mechanism proposed for these materials.