Application of some condensed uracils as corrosion inhibitors for mild steel: Gravimetric, electrochemical, surface morphological, UV-Visible, and theoretical investigations

Abstract

Gravimetric, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP) studies were carried out to investigate the comparative corrosion protection efficiency of four condensed uracils (CUs) on mild steel in 1 M HCl. EIS plots indicated that the addition of inhibitors increases the charge-transfer resistance (R ct), decreases the double-layer capacitance (Cdl) of the corrosion process, and hence increases inhibition performance. Moreover, the thermodynamic activation parameters for the corrosion reaction were calculated and discussed in relation to the stability of the protective inhibitor layer. The morphology of the surface was examined by scanning electron microscopy (SEM), and the surface composition was evaluated using energy-dispersive X-ray spectroscopy (EDX) to verify the presence of inhibitor on the mild steel surface. Quantum chemical study suggests that the heterocyclic rings in these compounds are structurally essential for the protection of the mild steel surface. © 2012 American Chemical Society.