电解液体系对镁合金微弧氧化涂层的影响

采用3种电解液体系对AZ91镁合金进行微弧氧化（MAO）处理。通过扫描电子显微镜和能量色散光谱观察涂层的表面形貌和元素组成,利用X射线衍射仪对涂层物相进行分析。同时,通过比较不同电解液体系微弧氧化涂层的粗糙度、润湿角和结合力来评估其特性,并利用极化曲线评价其耐蚀性能。此外,还使用模拟体液（SBF）浸泡实验来评估涂层的生物降解性能。结果显示：微弧氧化涂层具有良好的结合力;不同电解液体系处理得到的涂层在表面形貌和物相上存在差异,其中磷酸盐体系和硅酸盐体系具有较高粗糙度,而铝酸盐体系则具有较低粗糙度;此外,在各个系统中,磷酸盐体系呈现最小的润湿角值,而铝酸盐体系呈现最大值;这些差异导致了磷酸盐体系涂层耐蚀性最强,硅酸盐体系涂层次之,铝酸盐体系涂层耐蚀性最差;模拟体液浸泡21 d后的涂层表面产生了开裂,但耐蚀性得到了提高,这归因于浸泡过程中腐蚀产物和钙磷盐沉积物对于涂层的覆盖作用。

Effect of different electrolyte systems on the micro-arc oxidation coatings of magnesium alloy

Three electrolyte systems were used to get micro-arc oxidation (MAO) of the AZ91 magnesium alloy. Scanning electron microscopy with an energy dispersive spectroscopy was used to observe the surface morphology and analyze the chemical compositions of the MAO samples. The phase structure of the coatings was characterized by the X-ray diffraction. The characteristics of the coatings by different electrolyte systems treated were compared by using the roughness, wetting angle and binding force. The corrosion resistance of coatings was investigated by the potentiodynamic polarization curves. Besides, the biodegradability of coatings was evaluated by the simulated body fluid (SBF) immersion experiment. The results showed that the micro-arc oxidation coatings had relatively strong binding force. The coatings obtained by different electrolyte systems had different surface morphologies and physical phases. The phosphate and silicate systems had a higher roughness, while the aluminate system had a lower roughness. The phosphate system had the smallest wetting angle and the aluminate system had the largest wetting angle. These differences resulted in phosphate system coatings being the most corrosion-resistant, silicate system coatings being the second most corrosion-resistant, and aluminate system coatings being the least corrosion-resistant. The surface of the coatings cracked after 21 days of SBF immersion, but the corrosion resistance were improved. This is due to the covering effect of corrosion products and calcium and phosphate deposits on the coating during the immersion process.