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Analyzing the Corrosion Behavior and Evaluating the Mechanical Integrity of Biodegradable Magnesium Implants

Oswal, Mitesh

Abstract Details

2011, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.

Magnesium can be potentially used as biomedical implants owing to its biodegradability and biocompatibility due to its advantages over traditional metallic implants made from stainless steel, titanium, etc. Low corrosion resistance, however, hinders its use as implant material. Controlling the corrosion of magnesium is critical in the development of magnesium as a biodegradable implant. It is essential that the implant be mechanically strong even after moderate corrosion in order to be successful in supporting the damaged tissue. In order to design a better implant, it is necessary to evaluate the mechanical integrity of magnesium and magnesium alloys after corrosion. This work presents a simulation of the corrosion behavior of magnesium in a physiological environment, and also evaluates the mechanical integrity of magnesium alloys.

The simulation model for an electrochemical corrosion environment interaction between the magnesium as an electrode and the 0.15 M sodium chloride solution is developed using COMSOL Multiphysics software. It is a two-dimensional model based on Nernst-Planck equation for flux, and incorporates the simulation of the effect of anodization, a surface modification, to increase the corrosion resistance on an active magnesium surface. Corrosion behavior is simulated on a magnesium surface with and without anodized coating. The concentration distribution profiles of magnesium, hydrogen and hydroxyl ions species in the reactions are plotted. These results are compared in order to simulate the effectiveness of the anodized coating. The comparison of results from the simulation shows a substantial reduction in the concentration of magnesium, hydrogen and hydroxyl ions on the surface of an anodized coating, as compared to the active magnesium surface, in a sodium chloride solution.

Additionally, we evaluate the mechanical strength of AZ31 and Mg4Y magnesium alloys before and after corrosion using the tensile test method. The alloys are coated with a silane coating, and evaluated for their tensile strength after immersion corrosion in 0.15 M NaCl solution for four weeks. Stress vs. strain curves are plotted for both the materials for all the tests. The results for AZ31 show a reduction in strain to failure between corroded and uncorroded samples. This test is highly repeatable. The results for Mg4Y indicate a huge reduction in strain to failure for corroded samples, but this test is not repeatable. These results indicate that AZ31 is a much better material for implants, compared to Mg4Y, and even after corrosion.

Mark Schulz, PhD (Committee Chair)
YeoHeung Yun, PhD (Committee Member)
Vesselin Shanov, PhD (Committee Member)
David Thompson, PhD (Committee Member)
93 p.

Recommended Citations

Citations

  • Oswal, M. (2011). Analyzing the Corrosion Behavior and Evaluating the Mechanical Integrity of Biodegradable Magnesium Implants [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1311692279

    APA Style (7th edition)

  • Oswal, Mitesh. Analyzing the Corrosion Behavior and Evaluating the Mechanical Integrity of Biodegradable Magnesium Implants. 2011. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1311692279.

    MLA Style (8th edition)

  • Oswal, Mitesh. "Analyzing the Corrosion Behavior and Evaluating the Mechanical Integrity of Biodegradable Magnesium Implants." Master's thesis, University of Cincinnati, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1311692279

    Chicago Manual of Style (17th edition)