Gemini surfactant-functionalized di-Schiff bases: Tailoring hydrophobicity for corrosion protection of carbon steel in 1.0 M HCl

Abstract

This study investigates the correlation between surface parameters and corrosion inhibition performance of a series of gemini surfactants based on di-azomethine, with varying hydrophobic tail lengths—DSGO (8 carbons), DSGD (12 carbons), and DSGH (16 carbons)—for carbon steel in aggressive 1.0M HCl. Our study developed an effective corrosion inhibitor by fine-tuning the surfactants’ molecular structures. The activity of these surfactants as corrosion inhibitors was evaluated by measuring their gravimetric analysis under varying temperatures and was correlated with their surface activity. Our findings highlight that the hydrophobic tail elongating enhances the surfactants’ adsorption tendency with increasing the minimum surface area occupied by each unimer (A_min), thereby increasing adsorption capacity on the carbon steel surface. This structural modification improves inhibition efficiency, which is dose-dependent and positively correlated with both hydrophobic tail elongation and temperature. Langmuir adsorption isotherms indicate a chemical adsorption nature (ΔG_ads = −40.3 to −44.9 kJ/mol), with inhibition efficiency rising with temperature. Electrochemical Tafel analysis reveals that DSGO, DSGD, and DSGH act as mixed-type inhibitors. XPS and SEM surface examinations confirmed the effective adsorption of these inhibitors on carbon steel, demonstrating their strong affinity and efficacy in mitigating corrosion.