The CO2 erosion-corrosion electrochemical behavior of X70 pipeline steel was investigated under jet
impingement condition by high temperature and high pressure loop equipped with electrochemical
measure equipment. The surface morphologies and profiles of the X70 steel after jet impingement
experiment at different impinging velocities were characterized by scanning electron micrography
(SEM) and morphology profile apparatus. The results showed that the resistance to erosioncorrosion
of X70 steel decreased with the increase of impinging velocity. With the increase of
impinging velocity, the cathodic reactions of X70 steel were accelerated and anodic reaction rates
didn’t change obviously. The corrosion behavior of X70 steel shifted from activation and
mass-transport mixed-control to electrochemical-control. With the increase of the fluid velocities, the
maximum phase angles of X70 steel decreased gradually due to the change of double-layer
structure of electrode/solution interface. With the increase of the fluid impinging velocity, the constant
phase element of double layer Qdl increased and charge transfer resistance Rt decreased, due to the increase of the mass-transfer coefficient and wall shear stress with the fluid flow velocity. The erosion-corrosion profile was axisymmetrical basically, showing the “W” shape. The depth of
corrosion increased with the increasing of the radical distance, and then decreased.
Keywords: jet impingement, electrochemical characterization, erosion-corrosion, CO2 corrosion, X70
steel.