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ABSTRACT. The efficiency of three complex surfactants based on sunflower oil and nitrogen containing compounds as corrosion inhibitors for mild steel in CO2-saturated 1% NaCl solution, has been determined by weight loss and LPR corrosion rate measurements. These compounds inhibit corrosion even at very low concentrations. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive media. The inhibition efficiency increases with increasing the concentration of the studied inhibitors. Maximum inhibition efficiency of the surfactants is observed at concentrations around its critical micellar concentration (CMC). Adsorption of complex surfactants on the mild steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. Energy dispersive X-ray fluorescence microscopy (EDRF) observations of the electrode surface confirmed the existence of such an adsorbed film.

The new complex surfactants were synthesized based on sunflower oil and its inhibiting action on the corrosion of carbon steel in CO 2 -saturated oilfield formation water was investigated by means of weight loss and linear polarization resistance corrosion rate. The results revealed that the studied surfactants were excellent inhibitors. The percentage inhibition efficiency (IE %) increases by increasing the inhibitor concentration until the critical micelle concentration (CMC) is reached. The strong adsorption ability of the surfactant molecules leads to formation of a mono-layer, which isolates the surface from the environment and thereby reduces the corrosion attack on the surface. The adsorption process was found to obey the Langmuir adsorption isotherm.

Novel surfactants were synthesized based on corn oil and diethanolamine and its inhibiting action on the corrosion of mild steel in CO 2-saturated NaCl solutions was investigated by means of linear polarization resistance corrosion rate and polarization methods The results revealed that the investigated surfactants were an excellent inhibitors and the inhibition efficiencies obtained from two methods were in good agreement. The maximum inhibition efficiency was observed for inhibitor II (99.5 at 50 ppm). Polarization studies clearly revealed that the surfactants acted essentially as the mixed-type inhibitor. Thermodynamic parameters were obtained from polarization studies, which suggested that the adsorption of studied surfactants on metal surface obeyed Langmuir adsorption isotherm model.