Abstract
Inhibition of the corrosion of carbon steel in aerated 1.0 M HCl solution by acridin-9(10H)-one (Hydacr) was investigated by use of gravimetric, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy. Quantum chemical data were calculated by use of the density functional theory (DFT) model. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitor is of mixed type, and it inhibits the corrosion of the steel by blocking the active site of the metal. Changes in impedance parameters were indicative of adsorption of Hydacr on the metal surface, leading to the formation of protective films. Thermodynamic parameters led to the conclusion that adsorption is predominantly chemisorption. Quantum chemical calculations were carried out to investigate the corrosion-inhibiting property of Hydacr. Various parameters such as energy of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), softness of molecule were calculated and correlated with the inhibiting property of Hydacr.