AZ91D镁合金表面植酸转化时间对膜组织结构及耐蚀性的影响

Effect of Processing Time on Microstructure and Corrosion Resistance of Phytic Acid Conversion Coating on AZ91D Magnesium Alloy

为了进一步探讨工艺条件对镁合金表面植酸转化膜的影响,采用扫描电镜、能谱分析、点蚀试验和电化学测量等研究AZ91D镁合金表面不同成膜时间对植酸转化膜表面形貌、成分及其耐蚀性的影响规律。结果表明:植酸转化膜主要由Mg,Al,O,P,C元素组成,其中Mg的质量分数随成膜时间的延长而减小,而P的质量分数随成膜时间的延长逐渐增大;镁合金表面植酸转化膜表面裂纹宽度随成膜时间的延长而增大,且转化膜表层中裂纹的存在及大小不影响转化膜的耐蚀性;转化膜的存在主要影响合金电极阳极溶解反应机理,从而使合金的阳极溶解电流密度降低,对阴极反应机理影响不大。

Phytic acid conversion coating was prepared on the surface of AZ91D magnesium alloy.The effect of processing time on the morphology,composition and corrosion resistance of the conversion coating was analyzed by means of scanning electron microscopy,energy dispersive spectrometry,dipping corrosion tests and electrochemical measurements.It was found that the phytic acid conversion coating mainly consisted of Mg,Al,O,P and C.The content of Mg decreased with extending processing time,while that of P increased therewith.Besides,the width of the cracks on the conversion coating surface also increased with extending processing time,but the surface cracks had no effect on the corrosion resistance of the conversion coating.Moreover,the phytic acid conversion coating mainly influenced the anodic dissolution mechanism and led to decreased current density of anodic dissolution,but had little effect on cathodic reaction mechanism.