Improved corrosion resistance of Mg-Y-RE alloy coated with niobium nitride

Biodegradable magnesium alloys have attracted much attention in recent years due to their potential applications in cardiovascular stents and bone implants. However, their inadequate corrosion resistance in the physiological environment is a major obstacle limiting wider application. In this work, a niobium nitride (NbN) film is deposited on Mg-Y-RE alloy (WE43) by reactive magnetron sputtering to improve the corrosion resistance. The structure of the nitride film is determined by grazing incidence X-ray diffraction and X-ray photoelectron spectroscopy. The corrosion behavior of the uncoated and NbN-coated WE43 is evaluated in simulated body fluids by electrochemical impedance spectroscopy, polarization tests, and immersion tests. The surface morphology of the samples before and after the immersion tests is examined by scanning electron microscopy to assess the degree of corrosion. Our results indicate that the corrosion resistance is improved by the corrosion-resistant nitride film and the reasons are discussed.