CO₂ corrosion of X80 steel welded joints under micro-turbulence induced by welding reinforcement height

Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation. The welding reinforcement height (WRH) can induce locally micro-turbulent flow field, which aggravates local corrosion of welded joints. A high wall shear stress (WSS) experimental setup was established to conduct the online electrochemical corrosion test. The influence of WRH sizes on local corrosion of welded joints was studied at different flow rates. The electrochemical signals of the local corrosion of X80 welded joints at different flow rates were monitored in real time using electrochemical impedance spectroscopy and wire beam microelectrode. In addition, the corrosion products composition and properties were analyzed. The results show that the micro-turbulent flow fields induced by the WRHs can enhance ion mass transfer near the welded joints. The corrosion products on the WRH surface also present different microscopic morphologies at different flow rates. In strong flow fields, the locally enhanced WSS can peel off the dense corrosion product partially, leading to the electrochemical distribution of large cathode and small anode, which accelerates the occurrence and development processes of the local corrosion of welded joints. The scientific guidelines for the corrosion protection of long-distance oil and gas pipelines can be potentially provided.