New eco-friendly cationic surfactants: Synthesis, characterization and applicability as corrosion inhibitors for carbon steel in 1 N HCl

Three new environmental friendly surfactants of cationic type were synthesized using natural vanillin. Their chemical structures were determined using elemental, IR, 1H NMR and 13C NMR spectroscopic analyses. The surface activity of the synthesized surfactant solutions was determined using surface and interfacial tension measurements at 25 °C. The emulsification powers of these surfactants were measured against light paraffin oil. The biodegradation ability of the surfactants reached the maximum (75%) within 21 days. Corrosion inhibition characteristics of the green surfactants were determined on carbon steel in 1 N HCl at 25 °C using gravimetric and potentiodynamic techniques. The adsorption of inhibitors on carbon steel in 1 N HCl follows Langmuir adsorption isotherm. Thermodynamic adsorption parameters (Kads, ΔGads) of studied inhibitors were calculated using the Langmuir adsorption isotherm. The Tafel polarization results indicate that the inhibitors act as mixed inhibitors. The inhibition efficiency increases with an increase in the inhibitor dose, side chain length and surface activity of the inhibitors. The maximum inhibition efficiencies ranged between 95.09% and 98.53% at 400 ppm.

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► The modified vanillin Schiff bases cationic inhibitors were found to be effective inhibitors for carbon steel corrosion in 1 M HCl.
► The inhibitors act as mixed inhibitor.
► The increase of the alkyl chain attached to the inhibitor molecules increases their inhibition efficiency.