Mannich Base Analog as High-Temperature Corrosion Inhibitor for Carbon Steel in Oilfield Acidization: Experimental and Computational Study

Summary Acidization has emerged as a widely adopted technique to enhance productivity from carbonate reservoirs. To address the significant challenge of corrosion during high-temperature acid fracturing, in this work, a novel Mannich base corrosion inhibitor, N-(phenyl(pyrrolidin-1-yl)methyl)benzamide (PPMB), was synthesized. The corrosion inhibition performance of PPMB was assessed via the weight loss method. When PPMB was incorporated into 20 wt% HCl under conditions of 180℃ and 3 MPa, the corrosion rate of N80 carbon steel was markedly reduced to 61.60 g/(m2·h), achieving an inhibition efficiency of 97.20%. Comprehensive electrochemical, adsorption thermodynamic, and adsorption kinetic analyses revealed that PPMB adheres to the metal surface through physical adsorption, conforming to the Freundlich adsorption isotherm model. Additionally, molecular-scale investigations employing quantum mechanics software based on density functional theory (DFT) software elucidated the adsorption mechanisms of PPMB on metal surfaces (Frisch et al. 2010; Lu and Chen 2012). The findings demonstrate that PPMB primarily adsorbs via interactions between the electrons of its highest occupied molecular orbital (HOMO) and the d-orbitals of iron (Fe). This adsorption layer shields the metal surface from corrosive ions, resulting in effective corrosion inhibition.