Adsorption, temperature and corrosion inhibition studies of a coumarin derivatives corrosion inhibitor for mild steel in acidic medium: gravimetric and theoretical investigations

The corrosion inhibition features of a new eco-friendly coumarin derivative, namely, 4-((4-((4-hydroxy-3-methoxybenzylidene)amino)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)-methyl)coumarin (HATC), for corrosion of the mild steel surface in an acidic environment was studied using gravimetric techniques and quantum chemical calculations. It was concluded that the tested coumarin derivative is an excellent corrosion inhibitor with high inhibition efficiency. The inhibition performance increases with increasing concentration of the investigated coumarin (HATC) and decreases with increasing temperature. The mechanism of adsorption includes a physical adsorption mechanism. Theoretical studies done on the new coumarin molecule using the density functional theory (DFT) have shown that the most likely entities in coumarin molecules to bond to the metal surface are nitrogen, sulfur and oxygen atoms.