Assembly of succinic acid and isoxazolidine motifs in a single entity to mitigate CO2 corrosion of mild steel in saline media

Abstract

Inhibition of CO2 corrosion of mild steel in 0.5 M NaCl under atmospheric pressure at 40 °C as well as high pressure (10 bar) at 120 °C by 2-[2-methyl-4(or 5)-alkylisoxazolidin-5(or 4)-yl)methyl]succinic acids, a new class of molecules having inhibitive motifs of succinic acid, isoxazolidine and hydrophobic alkyl chain assembled in a single entity, has been examined by gravimetric and electrochemical methods. Inhibitor molecule containing CH3(CH2)8 outperformed its counterpart with a shorter hydrophobe CH3(CH2)4 and two other commercial imidazoline-based inhibitors. The effectiveness of these new inhibitors was also evaluated by electrochemical impedance spectroscopy. The inhibition efficiency by EIS was found to be 75%, 91% and 98% in the presence of 1, 5 and 20 ppm, respectively, at 40 °C. The potentiodynamic polarization studies indicated that the new inhibitors act as anodic inhibitors. The adsorption of the synthesized inhibitors follows Temkin adsorption isotherm model with favorable high values of –ΔG°ads and −ΔH°ads pointing the inhibitors adsorbed on the metal surface by chemisorption process. The XPS study confirmed the adsorption of the inhibitors on the metal surface. Keywords: Inhibitors, Mild steel, Polarization, Potentiostatic, Interfaces, Thermodynamic diagrams