Synthesis, Characterization, and Inhibition Potential of a Tosylate-Based Dicationic Surfactant for Mild Steel in Pickling Solution

This work aims to synthesize, characterize, and assess the ability of a novel tosylate-based dicationic surfactant (EDBT4) to inhibit mild steel corrosion in a 15% HCl solution (pickling solution). The surfactant was synthesized using well-established methods and characterized using various analytical techniques, including FT-IR, NMR (¹H and ¹³C), GC–MS, and TGA. These techniques validated the surfactant’s purity and structural elucidation. Weight loss, PDP, and EIS measurements examined the synthesized dicationic surfactant’s inhibitory efficiency. The outcomes indicate that EDBT4 is a highly effective corrosion inhibitor, demonstrating the highest efficiency of 95.0% at a concentration of 20 ppm. SEM, EDX, and XPS surface analysis techniques investigate the inhibition mechanism and provide information about the protective film that forms on the metal surface. The study explores the corrosion inhibition mechanism through potentiodynamic polarization in more detail and finds that EDBT4 is a mixed-type inhibitor. Based on the acquired data, EDBT4 adsorption on the metal surface follows the Langmuir isotherm model. The study also emphasizes the application of density functional theory (DFT)-based computational simulations, highlighting the critical roles played by the sulfonyl group (SO₂) and aromatic ring (C₆H₄^‒) on the charge sharing and adsorption of EDBT4. This DFT study clarifies the molecular interactions between the produced surfactant and the metal surface and offers a complete understanding of the surfactant’s performance as a corrosion inhibitor.