Oxides films are critical interfacial engineering attributes that govern the interaction between metallic biomaterials and the biological environment. Oxides are not always stable, and long-term performance characteristics are dependent on pre- use surface treatment methodologies and the specific in-use biological environment. For metallic biomaterials immersed in PBS, the dynamic in-situ varying temporal-spatial characteristics of oxide films such as morphology, electrical resistance and compositional change are not well understood. Stainless steel (SS) grade 316L was selected for this investigation. Atomic force microscopy coupled with electrochemical step polarization impedance spectroscopy were utilized as investigational tools to study the topographical and electrochemical changes of oxide films with hydration and under potentiostatic control, on mechanically polished and chemically etched surfaces. Phenomena of interest included oxide dome swelling upon hydration and changes in electrochemical and semi-conducting properties over time. X-ray photoelectron spectroscopy was used to characterize oxide film thickness, surface composition and depth distribution of constituent elements before and after extended immersion. The results of this study show that oxide films are not thermodynamically stable when exposed to PBS. Hydration induced enhanced growth of oxide film through lateral spreading of oxide dome islands. Potential had an influence on oxide film stability; reduction occur-red at cathodic potentials (e.g -1V). Oxides reformed at OCP, and were enhanced at more anodic potentials. Following 19 weeks of immersion, oxide films were enriched in Cr without significant noticeable change in thickness. These results indicate that processing affects the structure and chemistry of surface oxides, which in turn affects properties and performance. Physiological solutions result in significant changes in these oxides in terms of chemistry and morphology. These changes are also potential dependent and may not converge with long-term immersion but rather are affected by the initial characteristics.