X80管线钢在不同pH值红壤模拟溶液中的腐蚀电化学行为

Electrochemical Behavior of X80 Pipeline Steel in Simulated Red Soil Solutions with Different pH

采用动电位极化曲线、电化学阻抗谱(EIS)及三维视频显微镜技术研究了X80钢在不同pH值红壤模拟溶液中的腐蚀电化学行为。结果表明,pH值为5.5时,X80钢在红壤模拟溶液中的腐蚀受氧去极化控制,X80钢表面存在腐蚀产物结合层,EIS由高频不完整容抗弧和低频容抗弧组成;随着pH值的降低,X80钢的腐蚀逐渐转为电化学活化控制,自腐蚀电流密度逐渐增大,腐蚀阻力减小,腐蚀不断加剧;当pH值降至4.0~3.0后,X80钢表面出现大量蚀点,EIS低频区出现感抗特征。

The electrochemical behavior of X80 pipeline steel in simulated red soil solutions with different pH, which aim to simulate the corrosive medium of typical red soil at Yingtan area of the Southeast China was studied by potentiodynamic polarization curves, electrochemical impedance spectroscopy(EIS) and three-dimensional video microscope. The results show that the corrosion of X80 steel in simulated red soil solution is controlled by oxygen depolarization reactions when pH is 5.5; a corrosion products scale formed on the steel surface due to corrosion; the EIS of the corroded steel is composed of incomplete capacitive arc at high-frequency and complete capacitive arc at low-frequency. With increasing pH value, the corrosion processes of X80 steel gradually convert into being controlled by electrochemical activation, while its corrosion current density increases gradually and its corrosion resistance decreases. When pH value reduces to the range 4.0~3.0, numerous corrosion pits occur on the surface of X80 steel and correspondingly inductive arc appears in the low-frequency region of EIS.