植酸对纯镁超声微弧氧化层防护性能的影响

针对纯镁超声微弧氧化贯穿性孔隙问题,采用植酸对微弧氧化层进行转化处理,探讨对氧化层的防护性影响。利用扫描电镜(SEM)研究植酸处理前后氧化层的形貌,并借助能谱分析仪(EDAX)、傅里叶红外光谱仪(FTIR)以及电化学腐蚀工作站等检测手段分析植酸处理前后氧化层的化学成分、官能团构成、耐腐蚀性能等,并对植酸成膜机理进行研究。结果表明:随着植酸浓度的增加,超声微弧氧化层孔隙量减少,更加致密均匀,覆盖度提高,表面富含磷酸基和羟基。其中植酸处理浓度为7.5g/L时为最佳,其膜层C、P元素含量最高,Mg元素含量最低,氧化层的自腐蚀电位正移最大,自腐蚀电流密度下降,氧化层的防护性能最好。

Effects of Phytic Acid on Protective Performance of Film Formed on Pure Magnesium by Ultrasonic Micro-arc Oxidation

To decrease the perfoliate pore of the oxide film througth the ultrasonic microarc oxidation, phytic acid were adopted as conversion treatment. Its effect on protective performance of the film formed on pure magnesium by ultrasonic microarc oxidation were researched. The surface morphology, functional group and protective performance of micarc oxidation film before and after treated by phytic acid were studied by SEM, EDAX, fourier infrared spectrometer (FTIR) and electrochemical corrosion workstations, respectively. The results show that with the increasing of the phytic acid concentration, the pore amount of ultrasonic microarc oxidation film decreases, uniform density and coverage increases, and the film surface is rich in phosphate and hydroxyl. The samples show the best protective performance with most positive corrosion potential and lowest corrosion current and C and P element content on the film are the highest, while Mg element content is the lowest when the concentration of phytic acid is 7.5 g/L. Besides the formation mechanism of phytic acid conversion coating was also discussed.