Theoretical studies of some N,S-Compounds as corrosion Inhibitors for Mild steel in Acidic Medium

Density functional theory (DFT) at the B۳lyp/۶ -۳۱g (d,p) and HF/۶ -۳۱ G d۴p/ methods were performed or six N,S- Compounds for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was Bromo[۱,۲,۴]triazolo[۴,۳-a]pyridine-۳-thiol which corresponded with the order of most of the calculated quantum chemical parameters namely EHOMO (highest) occupied molecular orbital energy, ELUMO (lowest unoccupied molecular orbital energy, the energy gap ( ), The results showed that the calculated %IE of the N,S-Compounds. studied was found to be close to theirexperimental corrosion inhibition efficiencies.