Abstract
A novel class of quaternary ammonium-based cationic surfactants is synthesized and characterized via spectroscopic methods (FTIR, H-1 NMR and C-13 NMR). The surface properties, foaming power and biodegradability of the synthesized cationic surfactants are determined using the surface tension technique. The protection performance with their adsorption mechanisms for carbon steel is evaluated in a 15% HCl solution by a series of techniques including electrochemical impedance spectroscopy, potentiodynamic polarization curves, scanning electron microscopy (SEM), X-ray spectroscopy, and UV-visible spectroscopy. The surfactants are found to be excellent corrosion inhibitors for carbon steel. The results show that the inhibition efficiencies are increased by increasing the concentration and the hydrophobic chain length of the tested compounds reaching the maximum at 250 ppm. The potentiodynamic polarization curves suggested that the inhibitors behave as a mixed type with predominant cathodic inhibition and the corrosion behavior can be explained by the adsorption film mechanism. Moreover, the mode of adsorption obeys the Langmuir adsorption isotherm; also, the adsorbed layer on the surface of the metal is approved by using SEM.
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