SYNTHESIS AND INHIBITION PERFORMANCE OF DIQUATERNARY AMMONIUM GEMINI SURFACTANTS ON CARBON STEEL PIPELINES CORROSION IN GAS FIELD

摘要

Some quaternary ammonium Gemini surfactants were prepared, characterized, and evaluated as corrosion inhibitors for carbon steel in oil wells formation water containing sulfide ions. The effect of molecular structure on the inhibition efficiency was investigated by quantum chemical calculations. It was found that the inhibition efficiency increased with increasing the length of alkyl group attached to the tertiary nitrogen atom. The values of standard adsorption equilibrium constant and free energy of adsorption for the three inhibitors were calculated and discussed. The nature of protective film formed on carbon steel surface was studied using scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDX). The adsorption of the inhibitor molecules on carbon steel surface was found to follow Langmuir adsorption isotherm. The corrosion inhibition efficiency was measured by using electrochemical impedance spectroscopy (EIS) and Potentiodynamic polarization techniques. The data obtained from (EIS) were analyzed to model the corrosion inhibition process through equivalent circuit. The Tafel polarization results indicate that the inhibitors act as mixed type inhibitors.