Inhibition of carbon steel corrosion in HCl solution using N-oleyl-1,3-propanediamine based formulation

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The relatively environmentally benign ingredient diethyl-aminoethanol (DEAE) was introduced into the film forming amine (FFA) formulation based on the unsaturated diamine N-oleyl-1,3-propanediamine (NOPDA). The optimal FFA formulation was determined by orthogonal experiment. The high corrosion inhibition efficiency of 92.1% and the images of scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed the excellent corrosion inhibition effect of the improved FFA formulation in 1.0 M HCl acidic environment. The results proved that DEAE could promote the emulsification and dissolution of NOPDA in aqueous solution and therefore facilitate its adsorption onto carbon steel surface. The weight loss experimental results showed that the adsorption of the FFA inhibitor onto metal surface was endothermic and conformed to Langmuir isotherm model. Electrochemical impedance spectroscopy (EIS) analysis proved that a protective film was formed on the surface of carbon steel to prevent the transfer of charge. Contact angle measurements indicated that the film formed on the surface of the carbon steel was hydrophobic. According to X-ray photoelectron spectroscopy (XPS) analyses and thermodynamic calculation, it is inferred that the adsorption mechanisms mainly involved chemisorption, electrostatic attraction and hydrogen bonding. The results of this study provide a good reference for the application of unsaturated fatty diamine. • Weight loss and EIS experiments were carried out to investigate the anti-corrosion performance. • The emulsification and dissolution of NOPDA in water could be promoted by DEAE. • NOPDA-based formulation exhibited excellent corrosion inhibition performance in HCl. • FFA adsorption isotherm and thermodynamics were studied. • SEM, AFM and XPS analyses were performed and anti-corrosion mechanisms were inferred.