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通过在0.6 mol/L NaCl溶液中浸泡实验,研究重力砂型铸造镁合金AZ91D的耐腐蚀性能.采用光学显微镜、扫描电镜和XRD观察和分析腐蚀后的合金与生成的氧化膜.结果表明:合金在溶液中的腐蚀以点蚀开始,而后腐蚀介质通过点蚀坑向基体内部扩展;氧化膜的成分随着腐蚀时间的延长不断变化;氧化膜的晶界或缺陷处薄弱,易开裂,成为进一步腐蚀的通道;随着腐蚀的发展,氧化膜逐渐增厚,腐蚀速率呈下降趋势;由腐蚀速率的变化可以推测出不同成分的氧化膜的电极电位由里到外是逐渐上升的.
The corrosion resistance of gravimetric sand cast magnesium alloy AZ91D was studied by immersing in 0.6 mol / L NaCl solution.The corrosion and corrosion resistance of the alloy were observed and analyzed by optical microscope, scanning electron microscopy and XRD.The results show that the alloy The corrosion in solution begins with pitting, and then the corrosive medium expands to the inside of the matrix through the pits. The composition of the oxide film changes with the extension of the etching time. The grain boundary or defect of the oxide film is weak and easy to crack, resulting in further corrosion With the development of corrosion, the oxide film gradually thickens and the corrosion rate decreases. From the change of corrosion rate, it can be inferred that the electrode potentials of oxide films with different compositions gradually increase from the inside to the outside.