Synthesis, Characterization of Some Surfactants Based on Di-Oleamide and Evaluation of Their Efficiency as Corrosion Inhibitors for Oil Wells Tubing Steel under CO2 and H2Senvironment

Novel surfactants namely, N, N'- ( ( ( 2- (2- hydroxyethoxy) ethyl) azanediyl)bis ( ethane- 2, 1-diyl)) bis ( N- ( 2- ( 2-hydroxyethoxy) ethyl) oleamide) (I), N- ( 2 ( 2-hydroxyethoxy) ethyl) N, N bis ( 2 (N (2 (2hydroxyethoxy)ethyl)oleamido)ethyl)propan-2-aminium bromide (II) and N- (2- (2-hydroxyethoxy)ethyl)-N, N-bis (2- (N- (2- (2-hydroxyethoxy) ethyl) oleamido) ethyl)-4-methylbenzenaminium bromide (III), were synthesized, characterized by using FTIR and 1HNMR spectroscopic methods. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the performance of the synthesized surfactants as corrosion inhibitors for X-70 type tubing steel in deep oil wells formation water under CO2 and H2S environment at 25oC. Polarization curves showed that by increasing The inhibitor concentration the corrosion current density was decreased, and the presence of inhibitor molecules affect on both cathodic and anodic Tafel lines, 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 analysed 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 CO2 and H2S environment.