Influence of the composition of the liquid phase and the concentration of benzohydrazide on its effectiveness during cadmium electrodeposition from water-acetone perchlorate electrolytes

Abstract

Cadmium-benzohydrazide complexes (2 : 1) were found to be the main electroactive species in cadmium electrodeposition from water-acetone perchlorate baths. The discharge of these complexes is preceded by their dissociation at the cathode (zone of water structure stabilization) or in the bulk of the solution (zone of acetone structure stabilization). In the microheterogeneity zone of the mixed solvent, the complexes can be reduced from the adsorbed state. The process is best inhibited at low concentrations of benzohydrazide ((c ^o _L = 10⁻⁴ mol/l), when the electrode is covered with a very dense layer of adsorbed benzohydrazide and acetone molecules. With an increase in c ^o _L , perchlorate anions become more adsorbable, which is accompanied by increasing facilitation of the discharge reaction (Ψ′-effect). The strongest depolarizing effect of ClO ⁻₄ anions is observed in the zone of acetone structure stabilization, which is due to selective solvation of the anion and the desalting effect of the mixed solvent.