Kinetics of anodic behaviour of Pb in HCl solutions

The galvanostatic polarization technique was used to study the electrochemical behaviour of lead electrode in HCl solutions. The general shape of the resulting anodic potential–time curves is found to depend on magnitude of the imposed current density, the acid concentration and the temperature of the solution. The data of the curves were characterized by the presence of various regions due to different electrochemical processes. (i) A rapid and almost linear change of potential due to the decay of hydrogen overpotential and the subsequent charging of the electrical double layer at the metal/solution interface, (ii) a potential arrest corresponding to anodic dissolution of the lead to Pb 2+ ions, (iii) a linear rise in the electrode potential indicating the onset of passivity due to the formation of PbCl 2, (iv) a second potential arrest due to the chemical dissolution of the passive PbCl 2 layer, and (v) finally, a continuous rise in the Pb electrode potential with time. The electrode potentials corresponding to the different arrests were found to depend on the magnitude of the imposed current density, the acid concentration and the temperature of the solution. The duration time, τ, of the dissolution process was found to increase with the decease of the solution acidity and the current density and also with the increase of solution temperature.