GW93镁合金点蚀过程的原位监测及点蚀机制  

In-Situ Monitoring the Pitting Corrosion Process of GW93 Mg Alloy and Related Pitting Corrosion Mechanism

作　　者：宋影伟[1] 樊志民 董凯辉 单大勇[1] 韩恩厚[1] SONG Yingwei;FAN Zhimin;DONG Kaihui;SHAN Dayong;HAN En-Hou(Key Laboratory of Nuclear Materials and Safety Assessment,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China)

机构地区：[1]中国科学院金属研究所核用材料与安全评价重点实验室

出　　处：《中国材料进展》2020年第2期85-91,112,共8页Materials China

基　　金：国家自然科学基金资助项目(51471174);科技部“973”计划项目(2016YFB0301105)

摘　　要：镁合金作为最轻的金属结构材料有很多优异性能,但镁自身化学性质活泼,耐蚀性差,尤其易发生点蚀,破坏性和隐患性非常大。若想降低点蚀对镁合金部件安全服役性能的影响,就需要对镁合金点蚀机制有清楚的认识。然而,适用于其他金属材料的经典的点蚀机制是以形成氧浓差电池为基础,阴极发生的是氧还原反应,而镁合金阴极发生的是析氢反应,因此镁合金的点蚀形成过程尚需深入研究。采用扫描振动电极技术(SVET)原位监测了铸态GW93镁合金在3. 5%NaCl(质量分数)溶液中的点蚀过程,采用SEM观察了腐蚀过程镁合金微观形貌变化,采用电流-时间曲线对比了阴阳极电位对点蚀发展的影响。研究结果表明,点蚀坑外是微阴极,发生析氢反应,点蚀坑内是微阳极,发生镁的溶解反应,随着时间增加,点蚀发展过程是动态变化的。镁合金中第二相所导致的微电偶腐蚀加速效应及氯离子在腐蚀坑内的聚集,两者的协同作用驱动了点蚀不断向基体内部生长。Mg alloys,as the lightest structural metallic materials,have many excellent properties. However,the chemical activity of Mg is high,resulting in poor corrosion resistance. Especially,Mg alloys are susceptible to pitting corrosion with great destructiveness and hidden danger. To decline the negative effect of pitting corrosion on the safe service of Mg alloy parts,it is necessary to clarify the pitting corrosion mechanism of Mg alloys. The classical pitting corrosion mechanism of other metals is based on the formation of oxygen concentration cell,whereas cathodic hydrogen evolution reaction occurs on Mg alloys. Thus,the pitting corrosion process of Mg alloys needs to be investigated in detail. In this paper the pitting corrosion process of GW93 cast Mg alloy is monitored in-situ using SVET( scanning vibrating electrode technique) in 3. 5% Na Cl solution;the corrosion morphologies are observed using SEM( scanning electron microscopy);and the effect of cathodic and anodic potentials on the pitting corrosion process is compared using electrochemical measurements. The results indicate that the microcathodes locate in the outside of corrosion pits and hydrogen evolution reaction occurs there,while the microanodes locate in the interior of corrosion pits and Mg dissolution reaction occurs. The pitting corrosion process dynamically changes with increasing corrosion time. The synergistic effect of the microgalvanic acceleration resulted from second phases and enrichment of chloride ions in corrosion pits is the driving force for the propagation of corrosion pits towards the interior of Mg substrate.

关 键 词：镁合金 点蚀 第二相 扫描振动电极 原位监测 

分 类 号：TG174[金属学及工艺—金属表面处理]