摘要
为了提高镁合金磷化盐转化膜的耐腐蚀性能,向镁合金磷酸处理液中添加NH4VO3,采用中性盐雾实验、Tafel曲线和电化学阻抗测试、扫描电镜(SEM)测试和能量色散谱仪分析等方法检测膜层的性能,研究了NH4VO3对镁合金表面磷酸盐转化膜耐蚀性的影响。结果表明:加入NH4VO3后,镁合金化学转化膜表面的裂纹有细化和孔洞有减少的趋势;化学转化膜呈现明显的容抗特性,电化学阻抗可达273.6Ω;自腐蚀电位正移了121.6 mV,自腐蚀电流密度明显减小,降低了接近一个数量级,耐腐蚀性能得到了很大的提升,表面化学转化膜的耐中性盐雾腐蚀时间大幅度增加,达到41 h。
In order to improve the corrosion performance of the ordinary phosphate conversion coatings on AZ91D Mg-alloy, different doses of NH4VO3 were added to the phosphating solution to prepare the NH4VO3 modified phosphate conversion coatings. Then the corrosion performance, surface morphology, structure and composition of the prepared coatings were assessed by means of neutral salt spray test, Tafel curve and AC impedance measurement, scanning electron microscope(SEM) with energy dispersive spectrometer. The results show that compared with the ordinary phosphate conversion coating,the phosphate conversion coating doped with certain amount of NH4VO3 presents less pores and finer cracks on the surface, which become much more obvious with the increasing amount of NH4VO3 in the phosphating solution. The NH4VO3 modified conversion coating exhibits better corrosion resistance i. e.obvious capacitive reactance characteristics, higher electrochemical impedance up to 273.6 Ω and nearly one order of magnitude lower free corrosion current density etc. in the contrast to the counterpart. Besides, the neutral salt spray resistance of AZ91D Mg-alloy with the NH4VO3 modified phosphate conversion coating could reach up to 41 h, far higher than 8 h for that with the ordinary phosphate conversion coating.
作者
周志彬
冯毅
ZHOU Zhibin;FENG Yi(South China University of Technology,Mechanical and Automotive Engineering,Guangzhou 510640,China)
出处
《腐蚀科学与防护技术》
CAS
CSCD
北大核心
2019年第3期310-314,共5页
Corrosion Science and Protection Technology
关键词
镁合金
磷酸转化膜
偏钒酸铵
耐蚀性
magnesium alloy
phosphoric acid conversion coating
ammonium metavanadate
corrosion resistance
