Experimental and Quantum Chemical Studies on the Corrosion Inhibition Potentials of 2-(2-Oxoindolin-3-Ylideneamino) Acetic Acid and Indoline-2,3-Dione

The inhibition potentials of 2-(2-oxoindolin-3-ylideneamino) acetic acid (IG) and Indoline-2,3-dione (IS) was carried out using gravimetric and gasometric methods while the theoretical approach was investigated using quantum chemical principles. The results obtained, indicated that IG and IS inhibited the corrosion of mild steel in HCl solution through the mechanism of chemical adsorption. The adsorption of the inhibitors is spontaneous, endothermic and is consistent with El Awardy et al kinetic model. Application of Dubinin-Radushkevich adsorption isotherm also ascertained the prevalence of chemisorption mechanism. The Fukui function, global softness and Huckel charges on carbon and electronegative elements in IG and IS revealed that the site for electrophilic attack is in the pyrrole nitrogen while the site for nucleophilic attack is in the phenyl ring. It was also found that the inhibition potential of IG is better than that of IS because the presence of methylenecarbamic acid group in IG (=NCH2CO2H) facilitated better adsorption than the =O group in IS.