Benzimidazole Derivative and its Mixture as Novel Corrosion Inhibitors for Carbon Steel in High-Pressure Supercritical CO2 Environment

Abstract The carbon capture, utilization, and storage (CCUS) process plays a crucial role in reducing carbon dioxide (CO2) emissions. Additionally, CCUS-enhanced oil and gas recovery (CO2-EOR) is widely used. During CCUS process, CO2 exists in the downhole tubing as a supercritical (SC) fluid under high pressure. Severe corrosion occurs in the presence of water in supercritical CO2 environments. Corrosion inhibitors are among the most economical cost-effective methods for controlling corrosion. However, most conventional corrosion inhibitors are ineffective to control corrosion in high-pressure supercritical CO2 environments. In this study, the benzimidazole derivative 2-benzylthiobenzimidazole (BTBI) was investigated for its ability to inhibit the corrosion of carbon steel in high-pressure (10 MPa) supercritical CO2 at 60 °C. Additionally, the low molecular weight thiochemical compound 2-mercaptoacetic acid was studied to improve the inhibition efficiency. The corrosion inhibition mechanism and adsorption process were investigated by weight loss and electrochemical methods. The morphology and composition of the corrosion product films formed on the samples coupon surface after exposure to supercritical CO2 were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The results showed that the combination of BTBI and 2-mercaptoacetic acid exhibited a synergistic effect, significantly enhancing the corrosion inhibition. The optimal performance was achieved at a 1:3 ratio of BTBI to 2-mercaptoacetic acid, forming a more protective film on carbon steel. This protective film effectively inhibited the migration of corrosive media, reducing both general and localized corrosion. This study showed the potential of this novel inhibitor for inhibiting corrosion in challenging high-pressure supercritical CO2 environments.