Inhibition of API 5L X52 Pipeline Steel Corrosion in Acidic Medium by Gemini Surfactants: Electrochemical Evaluation and Computational Study

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The efficiency of three new synthesized Gemini surfactants (namely, A312, A314, and A316) of the type 4,4-[1,4phenylenebis(azanylylidene)bis(N,N-dimethyl-N-alkylaminium] bromide is evaluated as corrosion inhibitors for carbon steel API 5L X52 grade in 1M HCl. The relation between the experimental inhibition efficiency and theoretical chemical parameters obtained by computational calculation in order to predict the behavior of the organic compounds as corrosion inhibitors was instigated. The chemical structures were elucidated using 1HNMR spectra. Inhibition performance was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and weight loss tests. The polarization curves show that applied surfactants act as mixed type inhibitors. Nyquist plots showed the semicircle capacitive loop with different surfactants and concentrations. The inhibition efficiency orders are A312 > A314 > A316 with the highest efficiency of 94.87% for A312. Adsorption of inhibitors on API X52 steel surface was found to obey Langmuir isotherm. Theoretical evaluation of the inhibitory effect was performed by computational quantum chemical calculations. The molecule structural parameters (), (), energy gap (ΔE), and the dipole moment (μ) were determined. The results of experimental inhibition efficiency and theoretical calculated quantum parameters were subjected to correlation analysis.