Influence of bias voltage on corrosion resistance of TiN coated on biomedical TiZrNb alloy

Bare biomedical grade of titanium alloys are prone to undergo degradation in body fluid environment. Surface coating such as Physical Vapor Deposition (PVD) can serve as one of the alternatives to minimize this issue. In the past studies, effect of bias on corrosion resistance has received well attention but mostly on steel based implant materials. Similar study on the coated titanium based alloy is hardly found in the literature. In the present work, the effect of bias voltage (-50V to -200V) on PVD-TiN coated Ti13Zr13Nb biomedical alloy was studied. Scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) were used to evaluate surface morphology and crystal phase of the TiN coating respectively. Image analysis software was employed to quantify microdroplets counts. In addition, the corrosion behaviour was also evaluated using electrochemical test under the presence of Kokubo solution. Results show that the samples coated with -125V bias voltage provides the least number of microdroplets and results in highest corrosion resistance. It is also revealed that the presence of microdroplets on the coated substrate provides adverse effect to the coating performance by increasing their corrosion rates.