热镀锌层镧盐转化膜的结构及其耐蚀性能  

Microstructure and Corrosion Resistance of Lanthanum Salt Conversion Coating on Hot-Dip Galvanized Steel

作　　者：卢锦堂[1] 钟正[1] 孔纲[1] 

机构地区：[1]华南理工大学材料科学与工程学院,广东广州510640

出　　处：《材料保护》2009年第4期7-9,共3页Materials Protection

摘　　要：热镀锌件铬酸盐转化膜耐蚀性优良,但环境污染严重;铈盐转化膜效果差,复合铈盐转化膜耐蚀好,成本高;镧盐转化膜无毒,耐蚀效果比铈盐好。采用以La(NO3)3为主盐的成膜溶液浸泡热镀锌层,获得了La盐转化膜。通过SEM,EDS和电化学测试方法对La盐转化膜层的结构和耐蚀性能进行了研究。结果表明:转化膜随浸泡时间增加而增厚,膜的极化电阻和电化学阻抗也随之增大;膜层中存在均匀分布的微裂纹,且随膜增厚而扩宽;处理时间过长,膜的表层开裂脱落,极化电阻和电化学阻抗下降。浸泡30 m in所获La盐转化膜,极化电阻和EIS低频阻抗达20 kΩ.cm2以上,耐蚀性能远高于单一铈盐转化膜,极大地提高了热镀锌件的耐蚀性能。La salt conversion coating was obtained by immersing hot-dip galvanized ( HDG) steel in an aqueous solution contai-ning La( NO3)3 as the main salt. The microstructure and corro-sion resistance of the conversion coating were investigated by means of scanning electron microscopy (SKM ) , energy dispersive spectrometry (EDS) , and electrochemical impedance spectrosco-py (E1S). Results indicate that the thickness and polarization re-sistance of the La salt conversion coating increase with extending time of immersion. Many uniformly distributed cracks are present in the conversion coating, and the width of the cracks increaseswith increasing thickness of the conversion coating. Moreover, The corrosion resistance and electrochemical impedance of the conversion coating decreased with extending time of immersion, and the coating obtained at extended immersion duration was lia-ble to surface cracking and peeling off. After being immersed in the aqueous solution of La( NO3) 3 for 30 min, the resulting con-version coating had an impedance of 20 kΩ·cm2, showing much better anticorrosion ability than cerium conversion coating and ad-vantage in significantly improving the corrosion resistance of hot -dip galvanized steel.

关 键 词：镧盐转化膜 稀土 热镀锌 结构 耐蚀性能 

分 类 号：TG174.44[金属学及工艺—金属表面处理]