Corrosion inhibitors for carbon steel N80 in an acidic medium by using the compound (E)-N-(benzo[d]thiazol-2-yl)-1-(2,3-dihydro­benzo[b][1,4]dioxin-6-yl)methanimine

• A.M. Jabbar and A.S. Abdulnabi

Chemistry Department, Education College for Pure Sciences, Basrah University, Basrah 61001, Iraq

Abstract: A new heterocyclic organic corrosion inhibitor, the Schiff base [N-(benzo[d]thiazol-2-yl)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)methanimine], has been prepared by reflux distillation. Its properties have been analyzed by means of FT-IR, UV-Vis, ¹H NMR, ¹³C NMR, EI-Mass, SEM and EDS spectroscopic techniques. This synthesized chemical was used as a corrosion inhibitor in our study at various concentrations (0.0001, 0.0005, 0.001, and 0.005 M) and temperatures (298, 308, and 318 K) on carbon steel N80 in 1 M HCl and was studied by potentiodynamic polarization methods (Tafel plots). The findings proved that with an increase in concentration and temperature of the inhibitor, the percentage of inhibition efficiency (%IE) elevates. The most excellent corrosion inhibition efficiency of 95.71% was reached at 0.005 M at 318 K in 1 M HCl. The results of Sh1 as a corrosion inhibitor indicated that the adsorption of the inhibitor on the surface of carbon steel was of physisorption type and obeyed the Langmuir adsorption isotherm. Accordingly, we also studied the activation energy, and thermodynamic parameters were calculated from the Langmuir adsorption isotherm, including the free energy ΔG⁰, enthalpy ΔH⁰, and entropy change ΔS⁰. This electrochemical method (Tafel extrapolation) along with SEM and EDS techniques confirmed that this prepared inhibitor protects carbon steel from corrosion by forming a film (protection layer) on its surface.

Keywords: Schiff base, Tafel plot, adsorption isotherm, physisorption, Langmuir equation

Int. J. Corros. Scale Inhib., 2024, 13, no. 2, 1146-1163
doi: 10.17675/2305-6894-2024-13-2-27

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