Novel cationic Gemini ester surfactant as an efficient and eco-friendly corrosion inhibitor for carbon steel in HCl solution

The corrosion inhibition behaviors of a cationic gemini surfactant with hydrolyzable ester groups in its C-18 tails from natural palmitic acid were tested for carbon steel in 1.0 M HCl solution. The synergistic effect of the eco-friendly gemini ester surfactant with salt additives was explored. The corrosion inhibition efficiency was determined by weight loss measurement, potentiodynamic polarization and electrochemical impedance spectroscopy. The gemini ester surfactant exhibited high inhibition efficiency (94.5% at the concentration of 6.9 x 10(-5) M). Synergistic inhibition effect was observed between the surfactant and the salt additives, with the maximum corrosion inhibition efficiency as high as similar to 98.4%. The surfactant acted as a mixed type inhibitor with predominant inhibition of cathodic reactions. The adsorption behavior obeyed the Langmuir isotherm model with chemisorption between the inhibitor and carbon steel. Quantum chemical modeling indicates the formation of coordinate bonds between the surfactant and the metal surface. Surface analysis using SEM/EDS, AFM and water contact angle measurements confirmed the high effectiveness of the gemini ester surfactant on the protection of carbon steel in HCl solution, and the synergistic effect on corrosion inhibition between the surfactant and sodium salicylate was verified intuitively. (C) 2021 Elsevier B.V. All rights reserved.