| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 103 === Magnesium and its alloys are used in a broad range of applications including automobile, aerospace, communications and computer components owing to their excellent physical and mechanical properties, such as low density, high specific strength, good cast and weld ability, excellent electrical and thermal conductivity, high dimensional stability, and good electromagnetic shielding characteristics. Unfortunately, magnesium alloys possess lower corrosion resistance, especially in acidic environments and salt-water conditions. The ability to increase the corrosion resistance of magnesium and its alloys is crucial to increase the range of applications. To improve the fault, it is important to impart a high corrosion resistance without losing the superior physical and mechanical properties.
This study focused on the development of atmospheric pressure plasma jet (APPJ) system using tetraethoxysilane (TEOS)/O2 plasma under atmospheric pressure to deposit SiOx films on the surface of magnesium alloys in order to improve the resistance to corrosion. The material characterization results using X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy indicated that with increased O2 carried gas, the deposited thin films by APPJ were of inorganic SiOx nature. The potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements show that SiOx films coated on AZ91D alloys have more positive corrosion potential and lower corrosion current density than AZ91D substrates, indicating the corrosion resistance of AZ91D can be improved by depositing SiOx film on its surface. Finally, inorganic SiOx film at an O2 carrier gas flow rate of 1800 sccm after immersion in 3.5 wt.% NaCl solution for 72 h showed the better corrosion resistance than AZ91D alloy. The APPJ-deposited SiOx films represent an interesting alternative for improving the anti-corrosion performance of various materials in a cost-effective approach.
Keywords: magnesium alloys, Atmospheric pressure plasma deposition technique, inorganic-like silicon oxide (SiOx) thin films, anti-corrosion layers
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