The effects of parametric changes in electropolishing process on surface properties of 316L stainless steel

By Rahman, Zia ur; Deen, K. M.; Cano, Lawrence; Haider, Waseem
Published in Applied Surface Science NULL 2017

Abstract

Abstract Corrosion resistance and biocompatibility of 316L stainless steel implants depend on the surface features and the nature of the passive film. The influence of electropolishing on the surface topography, surface free energy and surface chemistry was determined by atomic force microscopy, contact angle meter and X-ray photoelectron spectroscopy, respectively. The electropolishing of 316L stainless steel was conducted at the oxygen evolution potential (EPO) and below the oxygen evolution potential (EPBO). Compared to mechanically polished (MP) and EPO, the {EPBO} sample depicted lower surface roughness (Ra = 6.07 nm) and smaller surface free energy (44.21 mJ/m2). The relatively lower corrosion rate (0.484 mpy) and smaller passive current density (0.619 ?A/cm2) as determined from cyclic polarization scans was found to be related with the presence of OH, Cr(III), Fe(0), Fe(II) and Fe(III) species at the surface. These species assured the existence of relatively uniform passive oxide film over {EPBO} surface. Moreover, the relatively large charge transfer (Rct) and passive film resistance (Rf) registered by {EPBO} sample from impedance spectroscopy analysis confirmed its better electrochemical performance. The in vitro response of these polished samples toward {MC3T3} pre-osteoblast cell proliferation was determined to be directly related with their surface and electrochemical properties.

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