• A novel benzotriazole-derived inhibitor (BTZ-D) was synthesized via Mannich reaction for CO₂ corrosion control in oil recovery. • BTZ-D exhibits high inhibition efficiency (94.79% at 60 °C and 86.52% at 120 °C/0.5 MPa CO₂) and significantly reduces pitting depth. • The inhibitor acts as a mixed-type adsorbate, forming a dense hydrophobic film, with adsorption following the Langmuir isotherm and driven by carbonyl and C–N= functional groups. This study aims to address the significant corrosion challenges faced by pipelines and equipment in CO₂-enhanced oil recovery (EOR) operations. It focuses on the development and evaluation of a novel benzotriazole-derived corrosion inhibitor (BTZ-D) to effectively mitigate CO₂-induced corrosion in aggressive saline environments. BTZ-D was synthesized via Mannich condensation using benzotriazole, formaldehyde, and cyclohexanone. Its corrosion inhibition performance was systematically assessed through static weight-loss tests, high-temperature/high-pressure dynamic experiments, electrochemical analyses (polarization and EIS), and surface characterization techniques (contact angle measurements and 3D microscopy). Adsorption behavior was modeled using the Langmuir isotherm, and the inhibition mechanism was further elucidated through quantum chemical calculations based on density functional theory (DFT). The inhibitor exhibited excellent performance, achieving a maximum inhibition efficiency of 94.79% for Q235 steel in CO₂-saturated brine at 60°C. Under harsh simulated conditions (120°C, 0.5 MPa CO₂), it maintained an efficiency of 86.52%. Electrochemical results confirmed BTZ-D as a mixed-type inhibitor, effectively suppressing both anodic and cathodic reactions. Surface analysis revealed the formation of a dense hydrophobic film, reducing the maximum pit depth from 41.9 µm to 18.2 µm. Adsorption followed the Langmuir model, indicating a spontaneous mixed physisorption-chemisorption mechanism. Quantum chemical calculations identified the carbonyl oxygen and C–N= nitrogen as key nucleophilic sites for coordination with the metal surface. This work presents the first comprehensive study on a benzotriazole derivative synthesized via Mannich reaction specifically for CO₂ corrosion inhibition in EOR applications. The integration of experimental performance evaluation with advanced surface characterization, thermodynamic modeling, and quantum chemical analysis provides deep mechanistic insights, establishing BTZ-D as a promising and rationally designed inhibitor for harsh oilfield environments.
Lian et al. (Sun,) studied this question.