Effect of oxygen and oxidizers on the corrosion and passivation of lead in chloride-free and chloride-containing acidic solutions

THE CORROSION and passivation behaviours of lead in chloride-free and chloride-containing acidic solutions were investigated. The metal is now considered to be one of the most polluting elements. The environmental problems accompanying the use of lead in many industrial applications make these investigationssufficiently important to warrant further intensive study. A comparison between the behaviour of the metal in oxygen-free and oxygen-saturated acidic solutions was made. The effect of hydrogen and nitrogen gases as an inert atmosphere was also studied using open-circuit potential measurements, polarization, and electrochemical-impedance spectroscopy (EIS). The corrosion-current density, i(corr), the corrosion potential, E-corr, and the corrosion resistance. R-corr, of the metal in each case were calculated. The electrode surface was analysed by x-ray photoelectron spectroscopy (XPS) and examined by scanning electron microscopy(SEM). The presence of oxygen in the solution increases the corrosion resistance of the metal. In dichromate-containing solutions, there was an optimum concentration of oxidizer at which the electrode surface acquires remarkable passivity due to the formation of a visible barrier layer of lead chromate on the metal surface. The presence of chloride ions increases the rate of corrosion of the metal. In the presence of dichromate, chloride ions were found to have insignificant effect on the corrosion rate of lead in acidic solutions.