Superior properties and behaviour of coatings produced on nanostructured titanium by PEO coupled with the EPD process

Abstract

Surface modification of commercially pure Grade 4 coarse-grained titanium (CG-Ti) and nano-grained titanium (n-Ti) by plasma electrolytic oxidation (PEO) and plasma electrolytic oxidation conjugated with electrophoretic deposition (PEO-EPD) processes is reported in the present study. Two different coatings were developed on each CG-Ti and n-Ti in phosphate-based electrolytes without and with the incorporation of hydroxyapatite (HA) nanoparticles. The phase composition, morphology (surface and cross-sectional), corrosion resistance, surface roughness, and scratch-resistance of the fabricated coatings were thoroughly studied and analysed. The L-929 fibroblast cells were used for assessing the in-vitro cell viability. The L-929 cells cultured on PEO-EPD treated CG-Ti, and n-Ti samples exhibited higher cell growth than PEO treated CG-Ti and n-Ti samples. Among all the PEO and PEO-EPD treated samples, the PEO-EPD treated n-Ti sample showed significantly better corrosion resistance (icorr = 8.85 × 10−7 mA cm−2), lower contact angle (40°), and good adhesion strength (Lc = 29 N), demonstrating the importance of the nanostructuring of the titanium substrate for the properties of the coating. The origin of the discovered enhancement in the properties of the modified PEO coating produced on nanostructured titanium was examined and discussed. After soaking in SBF for 14 days, the PEO-EPD treated sample is wholly covered with apatite layer indicating its good bioactivity.