Several newly synthesized triazoles including 1-(2aEuro(3)-nitrobenzyl)methenylideneamino-2-mercapto-5-(1'-(1',2',4'-triazol)) methenyl-1,3,4-triazole (NMTT), 1-(2aEuro(3)-methoxybenzyl)methenylideneamino-2-mercapto-5-(1'-(1',2',4'-triazol)) methenyl-1,3,4-triazole (MMTT), and 1-((4aEuro(3)-chlorobenzyl)methenylideneamino-2-mercapto-5-(1'-(1',2',4'-triazol)) methenyl-1,3,4-triazole (CMTT) were studied as corrosion inhibitors of mild steel in 1 M HCl by weight loss measurements, electrochemical experiments, and quantum-chemical calculations. The experimental results show that these compounds have high inhibition efficiency in the order CMTT >MMTT >NMTT. CMTT at concentration of 1.0 x 10(-3) M showed the highest inhibition efficiency of 96.4 %. The adsorption of the inhibitors on the metal surface obeyed the Langmuir isotherm, and the basic adsorption mechanism is proposed based on quantum-chemical calculations.