Electrochemical Behavior of the Lead Electrode in HCl and NaCl Aqueous Electrolytes

Abstract

The electrochemical properties of lead electrodes in aqueous chloride solutions were experimentally investigated over a range of 0.1 to 6.0 M HCl with the aim of extending previous work carried out only at 1.0 M HCl concentration. Experimental results using the rotating disc electrode technique, cyclic voltammetry, galvanostatic and potentiostatic charging conditions were employed in conjunction with spectroscopic studies of the electrolyte and X-ray powder diffraction analyses of electrode surface products. Experiments were also carried out in simulated sea water (3% NaCl) at different pH and compared with results obtained using HCl at the same molar concentration. At all chloride concentrations the overall reaction led to the formation of PbCl2 on the electrode surface, with the exception that in NaCl solutions where pH ≥ 6.5, Pb(OH)Cl was found to be one of the products. For concentrations of less than 0.4 M HCl, our results indicated that the diffusion of chloride ions to the electrode surface was the limiting factor in the formation of a passivating PbCl2 layer. At concentrations of about 0.7 M HCl, the electrochemical behavior showed a pattern of results which were interpreted in terms of a "passivation–dissolution" competitive mechanism consistent with the solubility minimum of PbCl2 in aqueous chloride solutions.