The paper presents the results of corrosion behaviour of brass in artificial tap water (ATW) and the inhibitor effect of mineral compound (M1) using two different electrochemical methods were used, classical potentiodynamic measurement and electrochemical impedance spectroscopy (EIS). The inhibitory effectiveness of corrosion increases with the concentration of inhibitor and reaches 86 % at 40 ppm. Potentiodynamic polarization measurements indicate that M1 compound is cathodic type inhibitor. Appropriate electric equivalent circuit model was used to calculate the impedance parameters. The values of the charge transfer resistance, obtained from impedance plots of brass, increased with increasing inhibitor concentration but those of capacity of the double layer decrease, leading to the formation of a protective film.