Electrochemical Deposition of Apatite/Collagen Composite Coating on NiTi Shape Memory Alloy and Coating Properties

Abstract

AbstractIn this investigation, an apatite/collagen composite coating was formed at 37C on a NiTi shape memory alloy (SMA) through electrochemical deposition using double-strength simulated body fluid (2SBF) which contained dissolved collagen. Surface characteristics, wettability and stability of the composite coating were subsequently studied. Scanning electron microscope (SEM) examination of the surface of composite coatings revealed that many collagen fibers were embedded in apatite with flake-like structure and apatite nanocrystals nucleated and grew on collagen fibrils. Energy dispersive X-ray (EDX) spectroscopy analysis showed that the Ca : P ratio of the composite coating was about 1.35, which is close to that of octocalcium phosphate. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) analysis were also conducted for the composite coating. Compared to bare NiTi SMA samples, the potentiodynamic polarization curves of NiTi SMA samples with the composite coating displayed lower corrosion current density, more positive corrosion and breakdown potential, suggesting that the composite coating was chemically stable and provided corrosion resistance for NiTi SMA.