A theoretical study of two isomeric molecules based on the thiatriazolic ring, namely 4-amino-1,2,3,5-thiatriazole (4AT) and 5-amino-1,2,3,4-thiatriazole (5AT), has been performed by resorting to a new model chemistry known as CHIH-DFT. The properties most relevant to their potential action as corrosion inhibitors has been calculated: dipole moment (μ), EHOMO, ELUMO, gap energy (ΔE) and several parameters that provide information about the chemical reactivity: electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (ΔN). Besides, the local reactivity was analyzed through the Fukui indices. All calculation have been performed by considering Density Functional Theory (DFT) using the gaussian03W suite of programs.