Comparative Assessment of Environment-Assisted Cracking Susceptibility of Different Grade API 5L Steels in CO₂, CO₂/H₂S, and H₂S Environments

The risk of hydrogen embrittlement (HE) and stress corrosion cracking (SCC) is a strong concern for material selection in the oil and gas sector. The presence of H₂S enhances hydrogen charging, which can increase hydrogen embrittlement (HE) susceptibility. There are knowledge gaps about HE in the environment saturated with pure carbon dioxide (CO₂) and with CO₂ containing H₂S. CO₂ has a strong impact on corrosion rate as well, enhancing cathodic reactions. CO₂ might also have a direct contribution to hydrogen charging and cracking mechanisms. This study addresses the assessment of hydrogen permeation and HE of X65 and X80 steels in CO₂ and/or H₂S environments. The performance of both steel grades is investigated, supported by experimental approach. The results indicate that the loss of mechanical resistance is due to hydrogen uptake and diffusion as well as the anodic dissolution, especially in Solution B. It is observed that X80 steel used in this work is more susceptible to cracking than X65 steel even in pure CO₂. It is concluded that the advantage of using a higher-mechanical-resistant steel, X80 can be suppressed by HE effects.