Synthesis of cyclocopolymer of pyrrolidine motifs containing hydrolyzed methionine residue and maleic acid as a corrosion inhibitor for mild steel in acidizing environments: Experimental and theoretical studies

The present study synthesized and examined the efficacy of cyclocopolymer of pyrrolidine motifs containing hydrolyzed methionine residue and maleic acid (CPMM) in inhibiting mild steel corrosion in an acidizing environment comprising 15 % HCl. The inhibitive performance was examined using gravimetric and electrochemical studies, including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). Scanning electron spectroscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed for a detailed surface analysis. The findings were further supported by density functional theory (DFT) and molecular dynamics (MD) simulations. According to weight loss analysis, CPMM exhibits considerable inhibitory capacity, achieving an inhibition efficiency (η%) of 87.1 % at a concentration of 100 ppm. At the same concentration, the addition of 2 mmol KI significantly increases the η% from 87.1 % to 93.2 % and maintains stability over a range of temperatures (303–333 K) for 24 h. The increases in η% from 87.6 % to 95.6 % and from 90.6 % to 97.2 % were found in EIS and PDP experiments, respectively. According to the PDP investigation, when the quantity of CPMM increased, the current density (i_corr) measurements continued to decrease. CPMM functions mainly as an anodic-dominant mixed-type inhibitor. According to the EIS evaluation, the charge transfer resistance (R_ct) figures showed an increase as the concentrations of CPMM increased. The adsorption isotherm analysis reveals that CPMM adheres to mild steel surfaces, following the Langmuir adsorption isotherm model. Both physical and chemical features of spontaneous adsorption were observed in CPMM, as demonstrated by the Gibbs free energy (ΔG_ads) values of −42.61 kJ mol⁻¹ (303 K) and −39.16 kJ mol⁻¹ (333 K). SEM and XPS data verified CPMM's surface defense and adsorption capabilities. Finally, DFT and MD revealed important interaction locations responsible for CPMM's potent adsorption. Those outcomes demonstrate CPMM's ability as an encouraging anti-corrosion material for use in acidizing industries.