Effect of Jet Impingement Velocity and Angle on CO₂ Erosion-Corrosion with and without Sand for API 5L-X65 Carbon Steel

Most oil and gas production wells have plenty of corrosive species present along with solid particles. In such production environments, CO₂ gas can dissolve in free phase water and form carbonic acid (H₂CO₃). This carbonic acid, along with fluid flow and with/without solid particles (sand or other entrained particles), can result in unpredictable severe localized CO₂ corrosion and/or erosion-corrosion (EC). So, in this work, the CO₂ EC performance of API 5L X-65 carbon steel, a commonly used material in many oil and gas piping infrastructure, was investigated. A recirculating flow loop was used to perform these studies at three different CO₂ concentrations (pH values of 4.5, 5.0, and 5.5), two impingement velocities (8 and 16 m/s), three impingement angles (15°, 45°, and 90°), and with/without 2000 ppm sand particles for a duration of 3 h in 0.2 M NaCl solution at room temperature. Corrosion products were characterized using FE-SEM, EDS, and XRD. The CO₂ EC rates were found to decrease with an increase in the pH value due to the increased availability of H⁺ ions. The highest CO₂ erosion-corrosion rates were observed at a 45° impingement angle in the presence of solid particles under all conditions. It was also observed that a change in pH value influenced the morphology and corrosion resistance of the corrosion scales.