On the kinetics of lead electrodeposition in fluorosilicate electrolyte Part I: Inhibiting effect of sodium lignin sulphonate

Abstract

The kinetics of lead electrodeposition in Betts type electrolytes was investigated by electrode impedance measurements. In the absence of additives, the complex plane impedance plots exhibit two separate capacitive features and a, low-frequency inductive loop. The sizes and proper frequencies of the capacitive loops are influenced by the current density, the electrode rotation speed and the presence of sodium lignin sulphonate (LS), a colloidal organic additive used in practice as levelling agent. The low-frequency inductive loop, connected to the active area where lead is deposited, disappears with the LS-containing electrolyte. A reaction model is proposed in which the charge transfer reaction is coupled to the formation of adsorbed complexed species able to inhibit lead deposition before diffusing towards the bulk solution. The inhibiting effect of LS additive is discussed in terms of changes in the kinetic parameters of reactions.