Construction of environment-friendly proline Mannich quaternary ammonium salt and its synergistic effect on corrosion inhibition of carbon steel

Acidizing represents a widely employed stimulation technique in petroleum reservoir development. Nevertheless, the inherent corrosivity of strong acids (e.g, 1 M HCl) towards downhole metallic infrastructure remains a critical operational challenge, potentially inducing premature equipment failure and substantial maintenance expenditures. To mitigate this corrosion phenomenon, the implementation of effective corrosion inhibitors has become an essential practice in oilfield operations.

In this study, we synthesized a novel Mannich quaternary ammonium salt corrosion inhibitor (designated as PMQ) through sequential Mannich condensation and quaternization reactions. The synthetic pathway employed L-proline, benzaldehyde, acetone and benzyl bromide as precursors. The corrosion inhibition efficacy of PMQ on N80 carbon steel (composition: Cr, 0.20; Mn, 0.92; S, 0.008; P, 0.01; Si, 0.19; C, 0.31; and Fe, 98.362) in 1 M HCl was systematically evaluated through Weight loss analysis and electrochemical techniques (CS310M). The results revealed that PMQ has good corrosion inhibition performance at 343 K. After adding 0.1 % wt (low concentration) PMQ, the corrosion rate of N80 steel in 1 M HCl hydrochloric acid solution is reduced to 7.32 g·m?²·h?¹, and the corrosion inhibition efficiency is 99.5 %. The adsorption of PMQ on the surface of N80 carbon steel conforms to the Langmuir adsorption isotherm, which is a mixed adsorption type including chemical adsorption and physical adsorption. The corrosion inhibition mechanism of PMQ on N80 carbon steel was analyzed by scanning electron microscopy, energy dispersive spectroscopy, contact angle measurement, molecular dynamics simulation and quantum chemical simulation. The results showed that PMQ forms a hydrophobic film on the metal surface through the electrostatic adsorption of the quaternary ammonium group and the π electron conjugation of the proline ring, which blocks the penetration of H⁺ and Cl^-, forms a dense protective film on the surface, inhibits the diffusion of corrosive medium to the metal surface, and effectively slows down the corrosion of the acid to the metal.

Dr. Ruiyv Bai is an energy materials researcher, specializing in the development of corrosion inhibitors and the study of corrosion mechanism. He holds a master 's degree in materials and chemical engineering from China University of Petroleum (East China). Dr. Ruiyv Bai has published articles on the development of new materials and catalysis. He is currently a doctoral student in the National Key Laboratory of Deep Oil and Gas of China University of Petroleum (East China).