Electrochemical behavior and corrosion inhibition of carbon steel using ethoxylated fatty alcohol surfactant / Mohammed Mahmoud Afifi Mahmoud ; Supervised Fakiha Eltaib Heakal

Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Physical Chemistry

The effect of the novel ethoxylated fatty alcohol 3,6,9,12,15,18,21-heptaoxatritriacontan-1-ol (AEO7) as a corrosion inhibitor for carbon steel in 0.5 M HCl solution at various temperatures ranging from 20 to 50 oC was investigated using weight loss, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization curves showed that the investigated surfactant acts mainly as mixed-type inhibitor. The results revealed that AEO7 is an effective inhibitor for carbon steel corrosion by forming an adsorbed layer on its surface. The inhibition efficiency of this green AEO7 compound increases with increasing its concentration but decreases with raising temperature. Addition of different doses from KI with 40 æM AEO7 greatly enhances the inhibition efficiency to reach ~ 96% at the highest tested KI dose of 1{u00D7}10-3 M. Kinetics and thermodynamic parameters of the activation process were evaluated and discussed. Effect of temperature revealed that AEO7 molecules can adsorb spontaneously on carbon steel surface according to Frendlich's isotherm via physisorpotion mechanism. The surface morphologies were inspected using scanning electro-microscope (SEM), optical profilometry and atomic force microscopy (AFM). Quantum chemical theoretical calculations using the density functional theory (DFT) were also applied for better understanding the relationship between the inhibition efficiency and molecular structure of the AEO7

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