On a Model for the Electrocrystallization of Zinc Involving an Autocatalytic Step

Abstract

The model presented involves the autocatalytic step Zn ~+ + Zr~+ads +e-2Zn+ads and the adsorption at the interface of three species, hydrogen, an anion, and the Zn 2+ cation which can be complexed. The model is compared with results obtained, after eliminating the influence of convective diffusion, during the electrocrystallization of zinc in: (i) an acid sulfate solution, (ii) a Leclanch~ cell electrolyte, and (iii) an alkaline zincate solution commonly used in accumulators. The experimental results are in good agreement with the model, although the three electrolytes are markedly different. The model accounts indeed for the variation of the electrocrystallization efficiency with the current, for the appearance of multiple steady states revealed by S-shaped current-potential curves, and for the existence of an inductive faradaic impedance characterized by at least three time-constants.

Studies of micromorphology and current efficiency of zinc electrodeposited from flowing chloride electrolytes

“…The evolution of hydrogen, the thermodynamically preferred reaction, is kinetically limited. Other researchers (46,60,61) have also reported that the current efficiency is independent of current in this region, in both acidic and alkaline electrolytes.…”

Optimization of electroless Ni–Zn–P deposition process: experimental study and mathematical modeling

“…As seen from Eq. (27), increasing the pH of the bath results in shifting the hypophosphite oxidation potential to more negative values. This shift in the hypophosphite oxidation potential causes the plating mixed potential to become more negative thus increasing the plating current density, as shown in Fig.…”

“…The equilibrium potential for each reaction is given by E eq,j = E 0,j + 2.303RT n j F log Πc oxi Πc red (27) where E 0 is the standard potential for each reaction. For simplicity, the activity of H 2 PO 3 − and HPO 3 2− is assumed to be unity for determining the equilibrium potentials of reactions (1) and (2).…”

“…The kinetic parameters used in the model for the different reactions to fit the experimental results are presented in Table 2 [21,22,26,27]. The kinetic parameters that were not available in the literature were assumed in this study.…”

Micro-scale mass-transfer variations during electrodeposition

“…According to Epelboin and co-workers [66][67][68][69], voltammetry and impedance studies show that zinc deposition is an auto-catalytic reaction. They argue that twoelectron transfer is unlikely, and that the reaction sequence must proceed in two con- Even with a slowly increasing current density, as in a voltammetric sweep, a small decrease in the kinetic overpotential may be detected in some cases.…”