Synthesis of Some Novel Cationic Surfactants and Evaluation of Their Performance as Corrosion Inhibitors for X-65 type Carbon Steel under H2S Environment

The inhibition efficiency of an sulphonamide derivative for X-65 type carbon steel in oil wells formation water under H2S environment has been studied by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. This sulphonamide derivative acts as a mixed-type inhibitor, which suppresses both cathodic and anodic processes by its adsorption on the electrode surface according to Langmuir adsorption isotherm, together with a slight positive shift in corrosion potential (E-corr). The surface properties such as the critical micelle concentration (CMC), the effectiveness of surface tension reduction (Pi(CMC)), surface excess concentration (Gamma(max)) and surface area per molecule (A(min)) have been determined by means of surface tension measurements. The obtained results showed that the percentage inhibition efficiency (eta%) was increased by increasing the inhibitor concentration until the critical micelle concentration (CMC) reached. Also, it was found that inhibition efficiency was increased by increasing both molecular size of the surfactant and introducing ethylene oxide units in the surfactant molecule. Potentiodynamic polarization curves indicated that the compounds under investigation act as mixed type inhibitors. The data obtained from electrochemical impedance spectroscopy (EIS) was analyzed to model the corrosion inhibition process through equivalent circuit. Finally, the nature of the protective film formed on carbon steel surface was analyzed by SEM and EDX techniques.