The corrosion inhibition properties of 2-(3-methyl-6-oxopyridazin-1(6H)-yl)accetohydrazide (GK1) for mild steel corrosion in HCl solution were analysed by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and gravimetric methods. The results of these techniques indicated that the inhibition efficiency increased with the concentration of inhibitor. Potentiodynamic polarization study clearly revealed that pyridazine derivative acted as mixed type inhibitor. EIS plots indicated that the addition of GK1 increases the charge-transfer resistance (Rct), decreases the double-layer capacitance (Cdl) of the corrosion process. Adsorption of inhibitor obeyed Langmuir adsorption isotherm model.