Study on Corrosion Behaviour and Corrosion Inhibitor of X65 Subsea Pipelines

Abstract

In this study, the corrosion behaviour and corrosion mechanisms of X65 pipeline steel was examined in different production processes by using high-temperature and high-pressure autoclaves, conducting electrochemical testing, and employing multiphase flow loops. In addition, the protective effect of a corrosion inhibitor was examined. The results indicated that at a CO₂ partial pressure of 0.04 MPa, the corrosion rate of X65 pipeline steel increased from 0.023 to 0.183 mm/a as the flow rate was increased from 0 to 4 m/s. This increase in the corrosion rate was attributable to an increase in wall shear stress caused by fluid flow, highlighting the effect of flow-accelerated corrosion. Under a CO₂ content of 0.39 %–10 % (with a partial pressure of 0.04–1 MPa), the corrosion rate of X65 pipeline steel increased from 0.085 to 0.293 mm/a with increasing CO₂ content. The addition of an LS-A-type imidazoline-based corrosion inhibitor concentration of 200 ppm, the corrosion inhibition efficiency reached 86.69 %.Study indicating high corrosion inhibition performance under field production conditions with temperatures not exceeding 40°C and flow rates not exceeding 4 m/s.