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A new Azo-Schiff base namly 6,6'-((1E,1'E)-(1,2- phenylenebis (azanylylidene)) bis (methanylylidene)) bis(3-(o-tolyldiazenyl)phenol) (A1) have been synthesized and characterized by elemental analysis, FT-IR,1H-NMR and Mass spectra. The new compound was evaluated as corrosion inhibitor for brass alloy in 0.5 M HCl, using weight loss . Weight loss measurements was studied at different temperatures and concentration and results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitors and the highest inhibition eﬃciency was obtained at an optimum concentration of (1×10-3 M) for inhibitor at 298 K . Thermodynamic parameters enthalpy of activation (Δ𝐻𝑎∗) , entropy of activation (Δ𝑆∗𝑎 ), and the activation energy (Ea) and for brass alloy corrosion and inhibitor adsorption, respectively, were determined and discussed. It has been determined that the adsorption for the studied inhibitors on brass complies with the Langmuir adsorption isotherm at 298 K, the calculated ΔGads values were found to be around -35 kJ mol-1, which indicates that inhibitor (Azo-Schiff base) is adsorbed on the brass surface by chemical and physical interactions. For further investigations DFT studies were employed to study the electrostatic potential and explain the nature of interaction between the inhibitor molecules and metal surface.