典型砂土盐渍土的电化学特性及其腐蚀性研究

Study on Electrochemical and Corrosion Characteristics of Typical Sandy Saline Soil

为了研究砂土盐渍土的电化学特性及其腐蚀性评价应用,通过正交助手和SPSS设计典型含易溶盐阴离子(Cl^-,SO_4^(2-)和HCO_3^-)砂土盐渍土的正交试验组,对砂土盐渍土的电化学阻抗特性及X80钢的电化学极化进行了测试。根据砂土盐渍土中电子、离子运动分布规律,建立了基本等效电路模型。砂土的阻抗谱高频端对应电极表面双电层电容和法拉第过程电阻,低频端对应于砂层的电容和电阻。砂土盐渍土的Nyquist图均呈现高频区容抗弧和低频区不同程度的扩散斜线。统计学极差分析显示,各种阴离子对等效电路参数的影响机理呈现一定的规律;砂土盐渍土对X80钢的腐蚀属于轻微的局部腐蚀,生成了铁的氧化物。三种阴离子共存的砂土盐渍土中,SO_4^(2-)对砂土电化学腐蚀行为影响较大;对腐蚀速率影响大小排序为SO_4^(2-)>HCO_3^->Cl^-。实际应用中根据电化学阻抗谱和极化电阻的测量值可以综合判断砂土的腐蚀性。

In order to study the electrochemical properties of sandy saline soil and its corrosive evaluation applications,orthogonal test groups of typical sandy saline soil containing soluble salt anions(Cl^-,SO4^2-and HCO3^-)were designed by orthogonal assistants and SPSS.The electrochemical impedance characteristics of sandy saline soil and the electrochemical polarization of X80 steel were tested.A basic equivalent circuit model was established according to the distribution laws of electron and ion movement in sandy saline soil.The high frequency region corresponds to the double layer capacitance on electrode surface and the resistance of Faraday process,and the low frequency region corresponds to the capacitance and resistance of the sand layer.The Nyquist diagrams of sandy saline soil all exhibit capacitive arcs(high-frequency area)and various degrees of diffusion slashes(low-frequency zones).The statistical range analysis shows that the effect of various anions on the equivalent circuit parameters presents a certain law.Corrosion of X80 steel in sandy saline soil belongs to slight localized corrosion.Among the three kinds of anions coexisting in sandy saline soil,SO 2-4 significantly affects the corrosion of sandy saline soil.The influence order of the anions on the corrosion rate is:SO4^2->HCO3^->Cl^-.In practical applications,the corrosivity of sandy saline soil can be comprehensively judged on the basis of the measured values of electrochemical impedance spectroscopy and polarization resistance.