A Sustainable Approach to Mitigate CO2 Corrosion by Leveraging Oxazolone Derivatives with Plant-Derived Extracts

Abstract

Sweet corrosion of pipeline steel remains a persistent operational burden for hydrocarbon producers, and it grows more pressing as reservoirs mature and produced fluids carry ever larger volumes of dissolved CO₂. Three oxazolone derivatives were prepared here by a one-pot, metal-free condensation and each was combined with leaf extracts of Eclipta alba and Moringa oleifera, furnishing six blended formulations that were screened as inhibitors for API5LX60 steel immersed in “3.5% NaCl saturated with CO₂”. The renewable fraction contributed by the extracts, together with the solvent-lean synthetic route, underpins the sustainability of the approach. Protection was quantified by coupon immersion and by three electrochemical routes — impedance spectroscopy, potentiodynamic polarisation and linear polarisation resistance, which returned mutually consistent efficiencies above 90% for every blend at the optimum dose of 100 ppm, establishing that the compounds examined are capable inhibitors. Surface coverage conformed to the Langmuir description, and values of ΔG°_ads between −24.6 and −25.7 kJ mol⁻¹ identified spontaneous adsorption of mixed physisorption-chemisorption character. The interfacial relaxation time lengthened roughly twenty-fold, from 1.60 s in the blank to 32.64 s at 100 ppm of the most effective blend, ONEA. Imaging and X-ray microanalysis of corroded and inhibited coupons (SEM, SEM-EDX) confirmed that a protective inhibitive layer had been laid down over the exposed metal.