Biotribology and biocorrosion of MWCNTs-reinforced PEO coating on AZ31B Mg alloy

Abstract

Over the last two decades, various methods have been developed for surface modification of Mg alloys among which plasma electrolytic oxidation (PEO) is one of the most effective methods for tailoring surface properties. However, PEO coatings still need to be improved in various aspects, including mechanical and corrosion performances. In the current study, multi-walled carbon nanotubes (MWCNTs) were incorporated into a PEO coating structure via one-step process. Characterization techniques in this study included scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). Corrosion behavior was evaluated by electrochemical tests taking into account quasi-in vivo conditions in order to get closer to implant degradation rates in human body. Dry-wear and tribocorrosion in SBF were also evaluated in reciprocal ball-on-plate mode. According to the findings, MWCNTs induced several microstructural modifications in PEO coating such as formation of ~ 1 μm homogeneous dense barrier layer and irregular-shape porosities. Reinforcement significantly improved pitting corrosion resistance of the PEO coating, yielded a low friction coefficient and decreased wear-related damage by 60%.