Electrochemical deposition and characterization of ZrO_2 ceramic nanocoatings on superelastic NiTi alloy

摘要

This study aimed to develop an appropriate nano-sized coating to prevent premature failures of NiTi components and nickel release to the human body. Two zirconyl salts, ZrOCl2 and ZrO(NO3)(2), were evaluated for electrodeposition as well as the effects of methanol and polyDADMAC addition. The surface morphology and chemical composition of the coated samples were evaluated using scanning electron microscopy with energy dispersive X-ray spectrometry, X-ray diffraction, and atomic force microscopy. The corrosion resistance was evaluated using potentiodynamic polarization tests in Hank's simulated physiological solution at 37 degrees C. The results showed that deposition using both ZrOCl2 and ZrO(NO3)(2) aqueous solutions reduces the surface roughness and improves the corrosion resistance of superelastic NiTi wires. When a ZrOCl2 methanolic electrolyte was used, the deposition was heterogeneous and cracks were observed in the film. The addition of polyDADMAC to aqueous and methanolic electrolytes resulted in more uniform coating surface and higher corrosion resistance in Hank's solution. The deposition of ZrO2 improved the corrosion resistance of NiTi wires even when no previous electrolytic polishing was applied. (C) 2018 Elsevier B.V. All rights reserved.