Electroplating of iron on AZ31 magnesium alloy for coronary stent applications
Drawbacks with permanent metal stents led to the investigation of alternative biodegradable stent materials. Potential biodegradable polymers for stents lack the mechanical strength as compared to metals used for stents. Magnesium (Mg) based materials are being investigated as a potential biodegradable metallic stent materials because of its biocompatibility and high strength to weight ratio. Magnesium possesses poor corrosion resistance in physiological environments, thus surface modification strategies on magnesium are needed. Challenges with surface coating on magnesium exist due to the high reactivity of magnesium. The objective of this thesis was to electroplate iron on AZ31 magnesium alloy. Iron being a part of human body and a major component of 316 L stainless steel, which is considered to be the gold standard of arterial stent was electroplated onto the surface of the AZ31 magnesium alloy. Iron was electroplated with an intermediate copper layer to prevent its interaction with the electrolyte and compared with the iron coating without an intermediate copper layer. The electroplated sample was characterized using SEM-EDX, XRD, XPS and roughness measurements. EDX analysis proved the presence of 40% iron by atomic weight. XRD analysis proved the presence of iron in magnetite form and XPS confirmed the presence of iron. The thickness of the sample was measured by SEM which was found to be 30.8µm. Roughness of the sample was measured using a digital microscope with surface analyzer using which the roughness was found to be 10.4776µm. Accelerated corrosion tests conducted in PBS proved that iron coated magnesium samples had better corrosion resistance than bare Mg. The corrosion rate of coated Mg was 1.373632mm/yr and the corrosion rate of bare Mg was 40.4114 mm/yr. This proves that iron coated Mg can be expected to stay longer in the body compared to the uncoated ones.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering