Modification of Pure Zinc Surface for Biomedical Applications: The Effect of Oxygen Plasma Immersion Ion Implantation on Tuning the Degradation Rate

Abstract

Zinc is a high-potential metal for biodegradable implants. The study of the surface properties, even if at a fundamental level, is of central importance because the surface is the place where electrochemical, physical, and biological interactions take place; this is critical especially for biomedical applications, in which these interactions affect each other. The present work investigates the effect of low-energy oxygen implantation, in the range of − 1 to − 5 kV, for different durations on commercially pure Zn, whose surface had been mechanically polished. The characterization of the as-received and implanted surface was carried out with standard and high-resolution electron microscopy, energy dispersive X-ray spectroscopy, sessile drop contact angle, X-ray photoelectron spectroscopy, and potentiodynamic tests. The plasma-treated surface showed distinct features related to the process parameters, such as the formation of surface waves and oxide agglomerates. The formation of an O-rich layer with specific morphological features was responsible for a slight modification of the corrosion rate, found to be generally lower for longer-time implanted samples being, for instance, ~  78 ± 26 μm year⁻¹ for samples implanted applying − 1 kV for 60 min compared to that of untreated samples, which is ~ 135 ± 9 μm year⁻¹.