Improved in-vitro corrosion performance of titanium using a duplex system of plasma electrolytic oxidation and graphene oxide incorporated silane coatings

In this study, pure and 0.1 wt% graphene oxide (GO) incorporated silane layers were deposited on plasma electrolytic oxidation coated titanium as biocompatible sealants using the sol-gel method. Thereafter, their corrosion protection performance was investigated during 14-day in-vitro immersion. The characterization revealed that the silane layers with amorphous structure covered surficial inherent defects of plasma electrolytic oxidation coated titanium and decreased surface roughness as well as hydrophilicity. Further, the embedment of GO nanosheets improved the integrity of the silane layer and caused a reduction in work of adhesion and surface free energy. Accordingly, the chemical affinity and dissolution kinetics of plasma electrolytic oxidation coated titanium in simulated body fluid (SBF) weakened such that the polarization resistance rose to 956.33 and 2213.69 k Omega.cm(2) after applying pure and GO incorporated silane layers, respectively. The electrochemical impedance spectroscopy demonstrated that the pure silane layer promoted the stability of the plasma electrolytic oxidation coated titanium from about 3 to 7 days. Also, the GO incorporated silane layer provided better stability to the end of 14 days and its protective performance was higher in the first 3 days. The SBF immersion test clarified that the bioactivity of the silane layers was higher than that of titanium due to the induction of particulate calcium-phosphate precipitations.