Ultra-low Young's modulus Zr-Nb thin films on Mg substrate for enhanced corrosion resistance

Abstract

Controlling the degradation rate of magnesium (Mg) via applying the (Zr-Nb) thin films was investigated in this study. The Zr-2.5Nb coatings were deposited on the Mg with thicknesses of 250, 450, 650, and 900 nm (hereafter named [email protected], [email protected], [email protected], and [email protected]), respectively. Grazing incidence angle X-ray diffraction of (Zr-Nb) coatings revealed the alpha phase of zirconium and dominant (002) texture, with the film thickness increasing from 450 nm to 900 nm. Potentiodynamic polarization, electrochemical impedance spectroscopy, and corrosion morphology observations in Dulbecco's Modified Eagle's cell culture medium (DMEM) solution revealed the (Zr-2.5Nb)-coated mg with the thickness of [email protected] sample provides the highest corrosion resistance compared to other studied thicknesses. [email protected] sample increases the corrosion potential from −1.49 V to −1.38 V and decreases the current corrosion density and corrosion rate from 149.32 (μA.cm−2) to 39.01 (μA.cm−2) and from 3.49 (mm.y−1) to 0.912 (mm.y−1), respectively. Further studies on the surface of the [email protected] sample in terms of nano-mechanical properties demonstrated that Young's modulus and hardness are 47.95± 4.43 GPa and 2.25± 0.41 GPa, respectively, which increases the hardness to reduced Young's modulus ratio, which is known as one of the important parameters in developing of temporary orthopedic implants, of the Mg from 0.03 to 0.06. Furthermore, nano-tribological measurements and atomic force microscopy observations confirmed that detachment or breakage are not observed. Zr-2.5Nb coating, owing to the influence only on the first stage of the degradation reduced the degradation rate of Mg surafce, and therefore, can be considered as a practical strategy for further development of Mg in orthopedic applications.