Date of Award

2013

Document Type

Thesis

First Advisor

Yun, Dr. Yeoheung

Abstract

The nature of magnesium alloys to degrade is attributed to the high oxidative corrosion rates which are attractive for a biodegradable medical implant since they will avoid a removal surgery by gradually degrading and being absorbed by the body. In this thesis project, the biocorrosion characteristics of AZ31 Mg alloy are investigated in a simulated physiological solution mimicking the airway surface lining fluid. Particular attention was focused on the effect of carbonate ions present in the solution and porcine stomach mucin added to the test solution to create an in vitro model of the epithelial mucus surfaces mimicking the epithelial surface along the trachea. The corrosion behavior of the samples was analyzed using both immersion and electrochemical tests. The morphological characterization of the samples was performed using X-ray computed tomography (Micro-CT) and scanning electron microscopy (SEM). Chemical composition of the surface corrosion products was determined with electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results showed that addition of bicarbonate ions accelerated uniform corrosion rate with the increase of bicarbonate concentration while mucin decelerated the corrosion rate of the samples by adhering to the surface thereby reducing the amount of corrosion products formed on the surface. In vitro cytocompatibility studies were performed using porcine tracheal epithelial (PTE) cells which proved to be non-toxic and biocompatible to the Mg alloy. The experimental data in this thesis project is intended to be used as foundation knowledge to predict the corrosion behavior of AZ31 Mg alloy in the physiological environment, in order to provide degradation information for future in vivo study to be utilized as a tracheal stent device.

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