Brass alloys are technologically important materials due to the wide range of their industrial applications. One of the important applications of these materials is their use as reservoirs and piping systems for heat exchangers, cooling systems and tap water. The electrochemical behaviour, corrosion and passivation of these materials in aqueous solutions and tap water under different conditions was investigated. The effect of some anions, especially Cl^-, on the corrosion and passivation behaviours of these alloys was studied. The corrosion parameters of the alloys, i.e. the corrosion current density, i_corr, corrosion potential, E_corr,and corrosion resistance, R_corr, were measured. Electrochemical impedance spectroscopy (EIS), open circuit potential measurements and polarization techniques have been used to investigate the electrochemical processes occurring at the electrode/electrolyte interface in the different solutions. The work is concentrated on the behaviour of three different brass alloys (75% Cu(I), 70% Cu(II) and 58.2% Cu + 2.5% Pb(III) and the rest is Zn) in aqueous solutions of different pH. The effect of oxygen and oxidizers on the corrosion and passivation behaviours of the different alloys was investigated. A comparison was made between the behaviour of the alloy and the behaviour of its constituent elements. Surface analytical technique have been used to confirm and to explain the results of the electrochemical measurements. In this respect, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used. In oxygen rich solutions, a decrease in corrosion the resistance of the alloy was recorded. The increased rate of corrosion was attributed to enhanced disproportionation reactions which lead to barrier film breakdown and destruction of surface passivity. The selective leaching of the active components enhances the disproportionation reactions also and higher rates of corrosion were recorded. The XPS and SEM results were used to confirm the suggested mechanisms by which the corrosion and passivation processes are taking place at the electrode/electrolyte interface.