温度和应力对管道钢应力腐蚀过程电化学行为的影响

Effects of Temperature and Stress on Electrochemical Behaviors of Pipe Steels in Stress Corrosion Process

为研究温度和应力对管道钢应力腐蚀过程电化学行为的影响,用X70钢和16Mn钢进行了试验,在不同温度、不同应力及慢拉伸条件下,用电化学极化测量方法研究0.5mol/LNa2CO3+1mol/LNaHCO3溶液中X70和16Mn管道钢的电化学行为。分析温度、应力(应变)和慢应变率等因素对极化曲线的影响,并讨论温度、应力和慢应变率对管道钢发生应力腐蚀开裂的驱动作用。试验结果表明:管道发生高pH应力腐蚀开裂的可能性随运行温度升高而增大;静应力使敏感电位区的阳极电流增大较显著,特征电位向负方向移动;管道钢材料在应力作用下,发生局部塑性变形,可造成选择性局部腐蚀,成为发生高pH应力腐蚀开裂的敏感部位。

The behaviors of pipeline steels X70 and 16Mn were studied in 0.5 mol/L Na2CO3+1mol/L NaHCO3 solution under a variety of temperatures, stresses and slow strain rates using the electrochemical polarization measurement technique. Effects of temperatures, stresses and slow strain rates on the polarization curves and the contributions of these factors to stress corrosion cracking (SCC) were also analyzed. The experiments showed that the possibility of high pH stress corrosion cracking would increase with the increase of operational temperature; static stress would enable the anode current to increase significantly at sensitive potential zone; characteristic potential would shift to negative direction; the material of pipeline steel produced local plastic deformation under action of stress and would cause selective local corrosion, therefore the area became a sensitive part of high pH stress corrosion cracking.