Development of novel multi-functional composite coatings on titanium: Evaluation of structural characteristics, bioactivity and corrosion behaviour

A multi-functional coating approach involving a sequence of surface modification is proposed to improve the corrosion resistance and bioactivity of Ti. Development of TiO2 nanotubular (TNT) arrays on Ti using ethylene glycol + 0.4 wt % NH4F + 10 wt % deionized water at 60 V for 60 min was employed as the first stage treatment. Electrodeposition of brushite over TNT arrays using 0.1 M Ca(NO3)(2) + 0.06 M NH4H2PO4 at 1 mA/cm(2) for 45 min was used as the second stage treatment. Some of the brushite coated TNT arrays were subjected to alkaline treatment using 1.0 M NaOH at 80 degrees C for 2 h to covert the brushite into hydroxyapatite (HAP) coating. Deposition of reduced graphene oxide/polycaprolactone (RGO/PCL) composite coating by dip coating method was adopted as the third and final stage treatment. The RGO/PCL composite coating is deposited over both brushite and HAP coated TNT arrays. The coatings formed at various stages were characterized for their morphological features, phase content and nature of functional groups. The corrosion behaviour of these coatings was determined by potentiodynamic polarization studies. The bioactivity of multi-functional composite coating was determined by immersing it in simulated body fluid (SBF) solution at 37 degrees C for 168 h while their long-term stability was determined by immersing it in HBSS at 37 degrees C for 21 days. The findings of the study reveal that the novel multifunctional composite coating on Ti is promising for bone tissue engineering. (C) 2020 Elsevier B.V. All rights reserved