2-Amino-5-phenyl-1,3,4-thiadiazole on condensation with benzaldehyde (SPT), 4-nitrobenzaldehyde (SNT), 4-methoxybenzaldehyde (SMT), 2-hydroxybenzaldehyde (SSTH) or 2-hydroxyacetophenone affords Schiff′s bases. Its molecular geometry and vibrational frequencies have been evaluated using the Hartree-Fock and density functional method (B3LYP). 2-Amino-5-phenyl-1,3,4-thiadiazole has been reported to inhibit the corrosion of mild steel in 0. 5M H2SO4 and 1. 0M HCl. Corrosion inhibition has been examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).