Development and Evaluation of Bio-Based Anionic Surfactants from Corn Oil for Corrosion Protection of Mild Steel

In response to increasing demand for sustainable alternatives to fossil-based materials, this study investigates the conversion of renewable feedstock into chemicals that offer reduced toxicity and lower production costs. The present study details the synthesis, purification, and evaluation of a green surfactantcorn oil-derived methyl ester sulfonate (COMES)and its purified variant (P-COMES) for corrosion inhibition applications. COMES was prepared through the transesterification of corn oil followed by subsequent sulfonation with chlorosulfonic acid. The product was further purified through washing, extraction, and solvent removal processes to obtain P-COMES. Characterization was performed using Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (¹H NMR) spectroscopy, confirming the successful introduction of sulfonate functional groups and the removal of impurities postpurification. Surface activity analysis revealed a significantly lower critical micelle concentration (CMC) for P-COMES (1 wt %, 22.7 mN/m) compared to COMES (2 wt %, 36.38 mN/m), indicating higher surfactant efficiency. The improved corrosion inhibition efficiency of P-COMES on C1018 carbon steel in 5 wt % NaCl solution was demonstrated by electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) measurements. At 1000 ppm, P-COMES corrosion inhibition efficiency reached 98.31% compared to 64.17% using COMES at the same concentration. SEM-EDS analysis further confirmed the development of a uniform and protective film on the surface in samples containing P-COMES. The results suggest that P-COMES, due to its enhanced amphiphilic structure and purity, functions as an effective and environmentally friendly corrosion-mitigating substance and suggests its suitability for industrial use in challenging saline environments.