晶粒细化对金属Cr在含Cl^-介质中腐蚀电化学行为的影响

Effect of refined grain size on corrosion behavior of metal Cr in media containing chloride ions

采用机械合金化通过热压烧结工艺制备了纳米晶金属Cr,利用动电位扫描法和交流阻抗技术,与常规尺寸金属Cr对比研究了它们在含Cl-介质中的腐蚀性能以及晶粒细化对其腐蚀电化学行为的影响。结果表明:随着Cl-浓度的增加,不同晶粒尺寸金属Cr的腐蚀电流密度增大,腐蚀速度加快。晶粒尺寸降低后,在相同条件下,腐蚀电流密度变大,其抗腐蚀性能降低。两种尺寸金属Cr的极化曲线均出现了钝化由强到弱交替变化的趋势,反映了Cl-对钝化膜的破坏与修复作用。两种尺寸金属Cr的交流阻抗谱均呈单容抗弧特征,表明腐蚀过程受电化学反应控制。

Nanocrystalline metal Cr was prepared by mechanical alloying through hot-pressing processes,and its corrosion mechanism and corrosion resistances in media containing chloride ions was investigated as compared with corresponding coarse-grained alloy.The results show that with the increment of chloride ion concentrations,the corrosion current densities increase and therefore corrosion rates become faster.After the grain size was refined,the corrosion current densities of nanocrystalline Cr are bigger than those of the corresponding coarse grained materials.This indicates that the corrosion resistances decrease when the grain size was refined.Two kinds of grain size metal Cr produce passivating phenomena,but they become weaker initially and afterwards stronger alternately with the increment of chloride ion concentrations.These results indicate chloride ion＇s action on destroying and restoration of electrovating film.The electrochemical impedance spectroscopy（EIS）of the two alloys in media containing chloride ions was composed of single capacitive loop,therefore corrosion process was controlled by electrochemical reaction.