A class of organic corrosion inhibitors namely; 2, 5-bis (4-dimethylaminophenyl)-1, 3, 4-thiadiazole (DAPT), 2, 5-bis (4-dimethylaminophenyl)-1, 3, 4-oxadiazole (DAPO), 3, 5-diphenyl-4H-1, 2, 4-triazole (DHT), 3, 5-di (4-pyridyl)-4H-1, 2, 4-triazole (PHT), 2, 5-bis (4-aminophenyl)-1, 3, 4-oxadiazole (PAOX), 3, 5-di (4-methylthiophenyl)-4H-1, 2, 4-triazole (4-MTHT) were investigated at density functional theory (DFT) B3LYP/6-31G**(d, p) level. The calculated molecular descriptors such as the HOMO, LUMO, the dipole moment, chemical potential (μ), chemical hardness (ղ), softness (s), global nucleophilicity (N) and average

Mulliken charges on nitrogen atoms are discussed in relation to the observed inhibitory efficiency for the compounds. The developed qualitative structural activity relationship (QSAR) models relate the calculated molecular descriptors to the corrosion efficiency; thus QSAR model predicted the experimental corrosion efficiencies. The possible sites for nucleophilic and electrophilic attacks on the compounds were analyzed through the Fukui functions.