Abstract
The corrosion and passivation behavior of lead brass (Zn-58Cu-1.8Pb) was investigated in acid, neutral chloride, and sulfate solutions under open-circuit and polarization conditions using EIS techniques. Corrosion of the alloy was caused solely by the dissolved oxygen depolarizer. CuCl and Cu sub 2 SO sub 4 together with some surface oxides were found to be corrosion products leading to passivation of the electrode surface. Impedance spectra in the form of Nyquist plots consisted of depressed semicircles with different degrees of depression. The depression was attributed to surface inhomogeneity and roughness. Ideal semicircles with high polarization resistance values were obtained at high cathodic potentials. This is attributed to the adsorption of anions and intermediates from oxygen reduction at the electrode surface. Potentiostatic polarization in the potential range -0.6 V < =V < =-0.2 V, led to selective dissolution of zinc and accumulation of CuCl or Cu sub 2 SO sub 4 films. At potentials > =-0.1 V pitting corrosion was observed.