气相环境中无机盐微粒沉积金属表面的电位分布

POTENTIAL DISTRIBUTION OVER THE METAL WITH SALT PARTICLE DEPOSITION IN ATMOSPHERE

使用扫描Kelvin探头参比电极技术研究了气相环境中无机盐微粒沉积诱发金属腐蚀过程的电位分布特征 .结果表明 ,金属电位分布的变化与无机盐的种类和环境相对湿度有密切关系 .在较低相对湿度下 ,无机盐的沉积不会改变金属表面均匀的电位分布 ;在较高相对湿度下 ,沉积无机盐位置的电位首先会形成电位深谷 ,然后深谷周围区域的电位逐渐升高 ,形成火山型不均匀电位分布 .Na2 SO4、NaCl和KCl等无机盐在Zn和钢表面沉积均可观察到这种电位分布的变化 .无机盐的沉积诱发的不均匀电位分布在金属表面形成了阴极区和阳极区 ,构成了腐蚀原电池 。

Potential distributions of atmospheric corrosion caused by salt particle deposition were investigated using scanning Kelvin probe technique.The results indicate that the changes in potential distribution depended on the type of the salts and the relative humidity of the environment.At lower relative humidity,the potential distribution over the metal with salt particle deposition remained uniform.When relative humidity is higher than RHoss(Relative Humidity over Saturated Solution),however,the potentials around the salt particle deposition shifted negatively,forming a lower potential valley,and then the potentials outside the valley gradually moved positively,leading to volcano type of the heterogeneous potential distribution.This phenomenon can be observed on zinc and steel with the salt particle deposition such as sodium sulfate,sodium chloride and potassium chloride.The nonuniform potential distribution caused by the deposition of salt particle built-up anode and cathode which forms corrosion battery on the metal surface.Then,the atmospheric corrosion was initiated and propagated.