金属镁在腐蚀介质中界面结构特征与负差数效应关系研究

STUDY ON THE RELATIONSHIP BETWEEN\=THE CORROSION INTERFACE STRUCTURE AND\=NEGATIVE DIFFERENCE EFFECT FOR PURE MAGNISUIM

利用扫描隧道显微镜，在微观尺度观察腐蚀界面形貌特征．发现ｐＨ＝１１的１ｍｏｌ／ＬＮａＣｌ水溶液中，金属镁表面形成块状氧化物，但微观尺度上氧化膜厚度不均，阳极化后块状氧化物尺度变小，保护作用降低，导致镁金属溶解出现负差数效应．金属镁在０．５ｍｏｌ／ＬＮａ２ＳＯ４和１ｍｏｌ／ＬＮａＣｌ两种介质中都产生负差数效应，但氧化膜结构不同。

The negative difference effect(NDE) phenomenon of magnesium has been studied by electrochemical measurement and STM. After observing the morphology characteristics on magnesium by STM in nanoscale, the newPartially Protective Film mechanism is proposed to explain the NDE phenomena. There were many oxide pieces which did not bulk up on the magnesium surface and the magnesium would be dissolved under the defect of oxide pieces when the anodic potential or current were applied on the electrode. It was shown that the possibility and the degree of NDE were decided by the structure of oxide on the magnesium electrode.\=