Structural and corrosion analysis of copper/chitosan coating on nanotubular TiO2/Ti6Al4V implant surface

Abstract

In this research, we focused on the investigation of the structural, surface, and corrosion behavior properties of copper-loaded TiO2 nanotubular array surfaces that were further deposited with a chitosan biopolymer. This composite material was fabricated on Ti6Al4V alloy substrates using a combination of anodic oxidation (AO), electro-cathodic deposition (ECD), and electrophoretic deposition (EPD) techniques, primarily to apply it in medical implant contexts. Initially, the TiO2 nanotubes were prepared via anodization (AO). Subsequently, copper was introduced into the TiO2 nanotubes through electro-cathodic deposition (ECD), followed by the coating of chitosan over the copper-loaded TiO2 nanotubes using electrophoretic deposition (EPD). To comprehensively assess the characteristics of these surfaces, a series of analytical techniques were employed, including SEM, EDX mapping, XRD, and wettability measurements. Furthermore, the electrochemical properties of these surfaces, namely the OCP, PDP, and EIS, were extensively scrutinized.The outcomes of this investigation directed a notable development in the electrochemical corrosion resistance of the chitosan-deposited copper-loaded TiO2 nanotubular array surfaces in comparison to uncoated Ti6Al4V alloy, particularly under conditions simulating a physiological environment (simulated body fluid, SBF). Corrosion rates, assessed through PDP (Potentiodynamic Polarization) curves, were determined to be 0.3023 mm/y for polished Ti6Al4V, 0.1476 mm/y for TiO2 30 V 4 h, 0.1235 mm/y for TNT-Cu2/30/Ch, 0.0733 mm/y for TNT-Cu2/60/Ch, and 0.0611 mm/y for TNT-Cu2/90/Ch. Additionally, corrosion protection efficiencies were calculated as 51.16 % for TiO2 30 V 4 h, 59.15 % for TNT-Cu2/30/Ch, 75.76 % for TNT-Cu2/60/Ch, and 79.81 % for TNT-Cu2/90/Ch. Notably, the TNT-Cu2/90/Ch sample demonstrated a significantly low corrosion rate of 0.0611 mm/year and a high corrosion protection efficiency of 79.81 %. This enhancement can happen due to the chitosan coating, which acts as a protective layer, hindering the ingress of the physical solution into the original metal surfaces. Notably, TNT-Cu2/90/Ch coated sample exhibited a corrosion rate (icorr) approximately 5 times lower than that of the uncoated alloy. In conclusion, this study presents a novel chitosan-coated composite material consisting of copper-loaded TiO2 nanotubular surfaces that effectively enhances corrosion resistance compared to polished Ti6Al4V substrates.