In this paper behavior of inorganic compound (2-amino-5-ethyl-1,3,4-thiadiazole) as inhibitor of copper corrosion in acidic medium (HCl solution) was examined. In addition to examination the effects of different concentrations of the inhibitor on the corrosion processes, research also included investigation of influence of immersion time of copper electrode in 2-amino-5-ethyl-1,3,4-thiadiazole (AETDA) solution on protective film formation on electrode surface (copper electrode). During this study next experimental methods are used: open circuit potential measurements (OCP), linear voltammetry measurements (LV) and cyclic voltammetry measurements (CV). Shift of open circuit potential toward negative values indicate that on copper surface comes to formation of corrosion product sand adsorption of molecule inhibitor. Copper oxidation is consequence of existing defect in structure layer and layer dissolution on electrode surface. Results show that inhibition efficiency depend on inorganic inhibitor concentration and immersion time of copper electrode in inhibitor solution (azole derivatives solution). Inhibition mechanism of AETDA is explained by forming compact protective film on copper surface. Adsorption of 2-amino-5-ethyl-1,3,4-thiadiazole on copper surface in 0.05M HCl solution obeys the Langmuir adsorption isotherm. The value of adsorption energy amount: ΔG = -39,52 kJ/mol.