X90钢热影响区在酸性介质中的电化学腐蚀行为

Electrochemical Corrosion Behavior of X90 Pipeline Steel and Its Heat-affected Zone in Acidic Medium

利用Gleeble 3500热/力模拟实验机对X90管线钢分别进行一次热循环及二次热循环,采用扫描电镜观察了X90管线钢原始组织及其热影响区的组织形貌,同时采用电化学方法研究和比较了X90管线钢原始组织及其热影响区在不同pH鹰潭模拟溶液中的电化学特性。结果表明,当溶液pH为3.3时,电化学阻抗呈现感抗特征,试样表面呈活化溶解状态,相对于X90的原始组织,晶粒较大的粗晶热影响区(CGHAZ)和临界粗晶热影响区(IRCGHAZ)试样表面活性较弱,具有更优异的耐蚀性;而当溶液pH为4.7及6.1时,电化学阻抗仅呈现容抗特征,组织表面呈带膜腐蚀状态,晶粒细化的细晶热影响区(FGHAZ)和过临界粗晶热影响区(SCCGHAZ)试样表面的产物膜较致密稳定,腐蚀电流密度较小,耐蚀性较好。

X90 pipeline steel was subjected to a thermal cycle and a secondary thermal cycle using a Gleeble 3500 heat/force simulation machine.The microstructures of the X90 pipeline steel and its heat-affected zone were observed by scanning electron microscopy.The electrochemical properties of the original structure of X90 pipeline steel and its heat affected zone(HAZ)in different pH Yingtan simulated solutions were studied and compared.The results show that when the pH of the solution was 3.3,the electrochemical impedance exhibitted an inductive resistance characteristic,and the surface of the sample was activated and dissolved.Relative to the original structure of X90,the coarse grained HAZ(CGHAZ)and the critical coarse grain HAZ(IRCGHAZ)had larger surface activity and better corrosion resistance,when the pH of the solution was 4.7 and 6.1,the electrochemical impedance only exhibited capacitive reactance characteristics,and the surface of microstructure was in a state of film corrosion,the product film on the surface of the grain refinement fine grain zone HAZ(FGHAZ)and the supercritical coarse grain zone HAZ(SCCGHAZ)was denser and more stable,the corrosion current density was smaller,and the corrosion resistance was better.