The Behavior of Zinc Electrode in Alkaline Electrolytes: II . A Kinetic Analysis of Anodic Dissolution

Abstract

A model for the kinetics of active zinc dissolution is developed taking into account the presence of an interfacial layer. From electrode impedance spectroscopy, it is shown that the metal dissolution takes place essentially at the base of pores in a conductive layer of oxidation products which is progressively degraded by the anodic current. This model accounts for the four loops observed on complex plane impedance plots with decreasing frequency: (i) a capacitive loop generally highly depressed in connection with the current penetration within pores; (ii) an inductive loop corresponding to the presence of a monovalent intermediate ZnI in the reactive interphase; (iii) a capacitive loop resulting from the precipitation and escape of ZnII ions by diffusion from the pore bases; and (iv) an inductive loop consequent on the slow decrease of the pore length with increasing anodic polarization. Inhibition of zinc corrosion by an organic additive is shown to be related to changes in both the kinetic parameters of reactions and the layer properties.

Hyper-dendritic nanoporous zinc foam anodes

“…The kinetic results evaluated from the Butler-Volmer fit at potentials of electrodeposited zinc at − 1.6 V and the standard bulk zinc is in agreement with the literature. [22][23][24][25][26][27][28][29] At applied potentials above − 1.6 V, more rapid kinetics were evident: we observed an increased exchange current of 36.8 ± 4.3 mA at − 2.0 V in comparison with 12.9 ± 0.5 mA for the standard. In addition to the evidence of more rapid kinetics, the anodic and cathodic Tafel slopes were calculated at 212.9 ± 5.1 and 190.1 ± 4.7 mV dec −1 at − 2.0 V in comparison with 125.6 ± 7.5 and 107.3 ± 1.5 mV dec −1 for the standard.…”

“…[22][23][24][25][26][27][28][29] Cathodic Tafel slope values of~120 mV dec −1 and cathodic charge transfer coefficient of~0.55 are suggested. The kinetic results evaluated from the Butler-Volmer fit at potentials of electrodeposited zinc at − 1.6 V and the standard bulk zinc is in agreement with the literature.…”

“…Historically, it has been limited by morphological uncertainty, which is dependent on local current density and pH. 8 Two typically undesirable regimes are ramification or the formation of dendrites that lead to electrical-short-circuits 9 and precipitation of ZnO 10,11 that can irreversibly passivate a surface. In conventional static zinc systems (composites, pastes and powders), these mechanisms lead to terminal failure, and in flow and flowassisted cells they can be reversed only at the cost of additional system overhead.…”

Comparative Study by Electrochemical Impedance Spectroscopy (EIS) On The Corrosion Resistance of Industrial and Laboratory Zinc Coatings

“…In the present study, the three relaxation processes are revealed only with concentration equals 1M. according to [4] the deformation of the left part of the capacitive loop HF is related to the existence of pores on the surface of the electrode. Moreover, the anodic reactions of dissolution does not appear only at their base i.e.…”

“…For instance, Deslouis et al [3] determined the kinetics of corrosion of zinc in aerated Na 2 SO 4 solutions and described a dissolution model. Corrosion was shown to occur essentially at the base of the pores of the coatings and progress of anodic dissolution gave rise to four loops with decreasing frequency [4] . Indeed, the compactness of the corrosion products layer developed on zinc needs to be introduced to evaluate its barrier effect [5] .…”