| Summary: | 碩士 === 國立高雄應用科技大學 === 化學工程與材料工程系博碩士班 === 105 === Protective composite coating were prepared on aluminum (Al) alloy by micro-arc oxidation (MAO) treatment plus a top coating with epoxy resin (Epoxy) system sealing agent and poly(methyl methacrylate) (PMMA) system sealing agent using immersion technique. MAO coatings on aluminum alloy are prepared in silicate electrolytes. Phase composition of MAO coatings are investigated by X-ray diffraction (XRD).The results showed that the MAO coatings are mainly composed of α-Al2O3 and γ-Al2O3 and the proportion of α-Al2O3 and γ-Al2O3 are affected by current density. Scanning electron microscopy (SEM) analysis of the MAO coating revealed the micro defect morphology with irregular porous structure. The effects of current density on MAO coatings were measured by thickness gage, hardness tester, coefficient of friction tester and surface roughness tester. Results showed that the thickness, hardness, coefficient of friction and roughness of MAO coating are significantly induced by current density. The silane coupling agents, 3-Aminopropyltriethoxysilane (APTES) and 3-Methacryl-oxypropyltrimethoxysilane (MPTMS) were used to modify the surface of the silica (SiO2). The properties of silane coupling agents modified SiO2 were characterized by Fourier transform infrared spectrum (FT-IR) and particle-size analyzer. The results showed that these modifiers are combined to surfaces of SiO2 by the covalent bonds. The microstructure of the MAO coating with epoxy system sealing agent and PMMA system sealing agent were analyzed by SEM. The results show that sealing agent was integrated with MAO coating by physically interlocking. Potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) results demonstrate that corrosion protection performance of epoxy sealed MAO coating on aluminum alloy remarkable enhances by embedding APTES-SiO2 nanohybrids. The adhesion test showed good adhesion between MAO and epoxy sealing agent coating.
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