Influence of diamond-like carbon coating on the corrosion resistance of the NITINOL shape memory alloy

The aim of this study is to modify the surface of Nitinol (Nickel Titanium Naval Ordnance Laboratory) alloy by covering with diamond-like carbon to improve the corrosion resistance and biocompatibility, and to prevent the toxic nickel ion release inside the human body. This alloy has unique properties, including shape memory effect and super elasticity, which make it an attractive candidate for biomedical applications. Diamond-like carbon (DLC) films were deposited by d.c. magnetron sputtering using a graphite target and argon as the discharge gas. The electrochemical characteristics of the DLC coatings were investigated by electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) at 37 degrees C in Fetal Bovine Serum (FBS). Surface analysis of the DLC coatings was conducted by means of X-Ray Diffraction (XRD), SEM and Vickers microhardness, and the thickness of DLC layer was measured using interferometry technique. The metallic ions release in bulk solution was studied by inductive coupling plasma-mass spectrometry (ICP-MS). In the case of uncoated samples, the release of metallic ions in bulk solution was much higher than in the case of DLC coated samples. Also, the corrosion resistance and Vickers microhardness of DLC-coated samples were improved in comparison with the uncoated samples. Copyright (C) 2010 John Wiley & Sons, Ltd.