Electrochemical Characterization of Erosion-Corrosion of X70 Pipeline Steel Under Jet Impingement Conditions

The CO₂ ejection corrosion experiments of X70 pipeline steel and 316L stainless steel under different fluid velocities and attacking angles at CO₂ partial pressure of 1MPa were investigated by a home-made high temperature and high pressure autoclave with a loop. The ejection corrosion rates under different ejection fluid velocities and attacking angles of the two steels were measured by mass loss method, and the surface and cross-section corrosion morphologies of the two steels were observed and analyzed by Scanning Electron Microscopy. Moreover, the interfacial velocities and stress including shear stress and compression stress of different fluid velocities and attacking angles were calculated by finite element method. The damage morphologies of the steels were compared with the calculation results of the finite element method. The results show that the corrosion rates of the steels increased with the increase of fluid velocities, and a peak value of corrosion rates appeared with the decrease of attacking angles from 90° to 10°. The nonuniform corrosion morphologies of the steels were closely related to the interfacial shear stress distribution from the infinite element calculation. The area of the specimens with the highest shear stress had the most serious damage. The correlation between corrosion morphologies and shear stress, compressive stress and fluid velocity were given respectively. The ejection corrosion behavior differences between the two steels as well as the reasons were also indicated.