Synthesis of Some Novel Surfactants Based On Di-Oleamide and Evaluation of Their Performance as Corrosion Inhibitors for X-70 Undersweet and Sourconditions

The main objective of this work was to examine the corrosion inhibition ability of three novel surfactant molecules synthesized from N, N'- ( azanediylbis ( ethane-2, 1-diyl)) dioleamide which named (I, II and III). Their chemical structures were confirmed using FTIR and 1HNMR spectroscopic methods. The surface active properties of the synthesized surfactants were calculated from surface tension measurements. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate their performance as corrosion inhibitors for X-70 type tubing steel in deep oil wells formation water under sweet and sour environment at 25oC. Polarization curves showed that by increasing the inhibitor concentration the corrosion current density was decreased, and the prepared surfactants acted as mixed type inhibitors. But the cathodic effect is more pronounced. Data obtained from EIS technique were analyzed to model the corrosion inhibition process through equivalent circuit (EC). Quantum chemical calculations based on ab initio method were performed on I, II and III. The molecular structural parameters, such as the frontier molecular orbital energy HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), and the fraction of electrons (-N) transfer from inhibitor to carbon steel surface were calculated and discussed. Finally, the nature of the formed protective film was analyzed by SEM and EDX techniques. The results showed that the selected surfactants have good efficiencies as corrosion inhibitors for tubing steel in deep oil wells formation water under sweet and sour conditions.