The influence of some arylazo indole derivatives on the corrosion rate of 70/30 á-brass in 2 mol 1-1 HNO3 was investigated using weight loss and galvanostatic polarization techniques. It was found that the investigated compounds behave as inhibitors. The inhibition efficiency increases with increasing the inhibitor concentration, but decreases with increasing the temperature. The adsorption of these compounds on the á-brass surface follows a Frumkin's adsorption isotherm. The electrochemical results indicated that all the investigated compounds act as mixed-type inhibitors. The influence of the substituent group on the inhibition efficiency of the inhibitor was explained in terms of the density of the electron cloud on arylazo indole moiety. Some thermodynamic parameters for corrosion and adsorption processes were determined and discussed.