Investigation of Anti-Corrosive Performance of a Si-Doped DLC-Coated Magnesium Alloy Stent Deposited by RF-Plasma CVD

The bioabsorbable magnesium alloy stent exhibits a high dissolution rate; therefore, it faces difficulty in achieving long-term vascular support rigidity. Thus, the control of dissolution rate using a diamond-like carbon (DLC) coating exhibiting excellent biocompatibility is studied. A conventional DLC is usually peeled off from the substrate when the stent expands. The Si-doped DLC (Si–DLC) is considered to be an elastic film candidate for solving this problem. However, the effectiveness of dissolution rate control has not yet been clarified. In this research, we intend to verify the corrosion behavior to confirm the possibility of controlling the dissolution rate of a bioabsorbable magnesium alloy coated with a Si–DLC film using a 13.56 MHz radio-frequency (RF) plasma chemical vapor deposition (CVD) apparatus. Further, the corrosion behavior was examined using electrochemical measurement by cyclic voltammetry. It was observed after repeated oxidation–reduction reaction that Si–DLC can not only drastically diminish the corrosion current value and the pH in the physiological saline solution but also suppress the local corrosion unlike the untreated magnesium alloy and DLC. Thus, the possibility of dissolution velocity control was confirmed.