陕北盐渍土壤对X80管线钢电化学腐蚀行为的影响

Influence of northern Shaanxi saline soil saturated with water on electrochemical corrosion behavior of X80 pipeline steel

采用电化学测试、SEM及EDS微观分析等方法,研究了X80管线钢在陕北水饱和盐渍土壤中的电化学腐蚀行为。结果表明,在水饱和盐渍土壤中,随腐蚀时间延长,X80钢腐蚀趋势和腐蚀速率均明显增大,局部腐蚀面积和深度不断增加,钢基体表面由以全面腐蚀为主转为以局部腐蚀为主,腐蚀机理为氧浓差腐蚀电池和局部腐蚀自催化效应,腐蚀速度主要受氧扩散过程控制;EIS图谱具有双容抗弧与Warburg阻抗特征,电荷传递和扩散传质的阻力随时间越来越大,而结合层电阻明显减小,这与钢表面生成腐蚀产物膜的完整性和致密性有关,腐蚀产物主要为铁的氧化物、硫化物和土壤中盐类的混合物。

The electrochemical corrosion behavior of X80 pipeline steel was investigated in northern Shaanxi saline soil saturated with water by using electrochemical measurement,scanning electron microscopy（SEM）and energy dispersive spectrum（EDS）analysis.The results showed that the corrosion tendency and corrosion rate of X80 steel significantly increased,pitting depth and area increased continuously,which was induced by change of corrosion morphology from uniform corrosion to localized corrosion.Corrosion mechanism was oxygen-concentration corrosion cell and localized corrosion autocatalysis effect,and corrosion rate was controlled by oxygen diffusion process.The characteristics of double capacitive reactance arcs and Warburg impedance could be found in electrochemical impedance spectra,the resistance of charge transfer and diffusion mass transfer in pitting became bigger and bigger,and binding layer resistance significantly decreased.It was dependent on the integrity and compactness of corrosion product films.The corrosion product was basically a mixture of iron oxides,iron sulfides and salts in soil.