钕铁硼合金在不同介质中的腐蚀行为

CORROSION CHARACTERISTICS OF Nd-Fe-B ALLOY IN DIFFERENT MEDIA

NdFeB永磁材料中钕的含量极高极易被氧化而产生严重的腐蚀,为提高钕铁硼材料的耐蚀性,首先应寻找NdFeB材料在不同介质中的腐蚀规律。对NdFeB材料在自来水、蒸馏水、氯化钠溶液、硫酸钠溶液、pH=1、3、5的硝酸溶液和pH=8、10、12的氢氧化钠溶液中不同温度下的腐蚀特性进行了研究,并测试了以上介质中NdFeB的阳极极化曲线。实验表明:在同种溶液中NdFeB腐蚀速度随温度的升高而加快;随pH值的增加而减小,当pH大于10时基本无失重;极化曲线验证了静态浸泡试验的结果。从扫描电镜可以看出NdFeB在氯化钠、蒸馏水、自来水及酸性介质中的腐蚀形态主要是晶间腐蚀和选择性腐蚀,氯化钠介质中还表现有小孔腐蚀。

Nd-Fe-B permanent magnet materials are corroded and oxidized seriously due to a high content of Nd. In order to improve the corrosion resistance of NdFeB materials, the corrosion regulation in different media should be investigated. The corrosion characteristics of a Nd-Fe-B materials were studied in tap water, distilled water, NaCl solution, Na2SO4 solution, nitric acid solution of pH=1,3,5 and sodium hydroxide solution of pH=8,10,12 at different temperatures. The anodic polarization curves of Nd-Fe-B were measured in these media. The higher the temperate, the quicker the corrosion rate in the same solution. The corrosion rate decreased with the increase of pH. There was no weight loss when pH was higher than 10. The experiment results of static state immersion in these media were validated by polarization curves. SEM observation showed that the corrosion modes of NdFeB were intergranular corrosion and selective corrosion in distilled water, tap water, acidic media and NaCl medium. There was pitting corrosion in NaCl medium also.