Investigation of the Corrosion Inhibition Effect of Two Piperazine-Based Ligands on Carbon Steel in Molar Acid Medium

Abstract

In this study, the corrosion data of carbon steel for free and containing inhibitors of 1,4-bis(2-(2-hydroxyethyliminomethyl)phenyl)piperazine (1) and its reduced form, 1,4-bis(2-(2-hydroxyethylaminomethyl)phenyl)piperazine (2) in 1.0 M HCl solution were calculated. The various concentrations of inhibitors, 0.2, 1.0, and 2.0 mM, were used to explore the inhibition ability of the synthesized materials against carbon steel corrosion. The change of OCP, open circuit potential, detected by variation of the type of inhibitors and concentrations in the range of 0-2.0 mM, was evidence of rearrangement of cations and anions on the electrode surface. From potentiodynamic studies, the inhibition efficiency was enhanced as the inhibitor concentration increased in the order of (2)>(1). The corrosion efficiency of carbon steel in 1.0 M HCl attained a maximum value of 66.08% for (1) and 88.51% for (2) when the concentration of inhibitor reached the highest value. The results obtained from electrochemical impedance spectroscopy, EIS, illustrated that the capacitance of the double layer, C dl , decreased with an increment of inhibitor concentration. As the same time, the charge transfer resistance of carbon steel enhanced as the inhibitor increased, which is in accordance with the variation of corrosion current density derived by the Tafel diagram. Adsorption of both inhibitors, compound (1) and its reduced form (2), was found to obey Temkin adsorption isotherm, in which the (2) had higher strength between the adsorbate and steel surface compared to compound (1).