The inhibition activity analysis of these organic inhibitors was made by assuming that the mechanism of inhibition by organic molecules is chemisorptions. We presume that, these organic inhibitors inhibit corrosion of carbon steel by a protective mechanism, forming insoluble iron complexes and repairing the porous oxide layers. The addition of the organic inhibitors led in all the cases to inhibition of the corrosion process in acidic solution at different temperatures. At concentrations lower than critical micelle concentration (CMC), the inhibition of these three surfactants is negligible and at concentrations higher than the CMC, the inhibiting action of these inhibitors increases rapidly. Polarization curves indicate that they are mixed type of inhibitors. The inhibition efficiency was high in all the studied cases. The corrosion parameters obtained from polarization curves and from EIS spectra are in good concordance and point out the inhibitory action of cationic surfactants. The adsorptions of the organic compounds on the carbon steels surface obeyed Langmuir’s isotherm. The thermodynamic parameters of adsorption enthalpy (ΔH0), adsorption free energy (ΔG0) and adsorption entropy (ΔS0) were calculated. Further characterization using Fourier transform infrared spectroscopy (FT-IR) demonstrates the adsorption of organic inhibitors and the formation of corrosion products on the carbon steels surface. The inhibition process was attributed to the formation of the adsorbed film on the metal surface that protects the metal against corrosive agents. The EIS measurements have confirmed this protection and pointed out the formation of adsorption layers on the electrode surface.
