| Summary: | 碩士 === 國立中興大學 === 材料科學與工程學系所 === 106 === Magnesium alloy materials have been approved and widely used in the global medical market nowadays. Although magnesium alloy has poor corrosion resistance, it is the
biodegradable metal in biomedical applications. The main objective of this study was to improve the corrosion resistance of AZ31 magnesium alloy. Using electrolytic deposition HAp/ZrO2 composite coating on this alloy, the optimum process was searched by tuning different deposition parameters. In the experiment, the magnesium alloy AZ31 specimen was immersed in the solution of sodium hydroxide (NaOH) for forming the passivation film. Consequently, the electrochemical deposition of zirconia (ZrO2) is carried out in ZrO(NO3)2 aqueous solution, finally forming the composite coating of HAp/ZrO2 in a mixed solution of Ca(NO3)2·4H2O and NH4H2PO4 also by the electrochemical method. Through sintering, the composite coating can form a more stable bond with the alloy specimen. The prepared specimens were characterized by scanning electronmicroscope (SEM), X-ray diffraction (XRD) and dynamic polarization tests to analyze and discuss the coating structure and corrosion resistance. The results show that the corrosion resistance of HAp/ZrO2 composite coated specimen in better than that of single-layer HAp coated one by the immersion method or the and uncoated one in 3.5wt% NaCl, leading to the current density of Icorr decreased from 136.51 to 20.162 μA/cm2. It is concluded that magnesium alloy AZ31 could be a biodegradable material used in impants after the improved corrosion resistance.
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