Dynamic Electrochemical Properties and Degradation Behavior of Coated High-Purity Magnesium

In this study, using micro-arc oxidation (MAO), electroless nickel plating, physical vapor deposition (PVD), and plasma-enhanced chemical vapor deposition (PECVD) techniques, we successfully prepared two types of composite coatings on high-purity magnesium surfaces: high-purity magnesium surface/micro-arc oxidation/electroless nickel/ titanium carbide composite coatings and micro-arc oxidation/organic C x O y Si thin film (PM/MAO/Ni/TiC and PM/MAO/CₓO y Si) on high-purity magnesium surfaces. Using a self-developed microfluidic electrochemical testing system to simulate the dynamic human body fluid environment, the electrochemical curves of high-purity magnesium-coated samples were monitored in situ after 16 hours of immersion. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were employed to analyze the coated samples and their corrosion morphologies after 16 hours and 7 days of static and dynamic immersion. The results indicate that, compared to static immersion, the capacitive arc of high-purity magnesium-plated samples in the dynamic group decreased by up to 5×10 5 Ω·cm 2 , the charge transfer resistance decreased by up to 3.77×10 3 Ω·cm 2 , the carrier concentration increased, and the average degradation rate after seven days of immersion reached up to 0.2615 mm/y. These results indicate that a flowing aqueous environment accelerates the transport of corrosive media and the degradation process of the coating.