The influence of sorbitol on zinc film deposition, zinc dissolution process and morphology of deposits obtained from alkaline bath

Abstract

A novel cyanide-free zinc deposition bath was developed in which sorbitol was added at various concentrations. Voltammetric studies indicated that the reduction process is influenced thermodynamically and kinetically by the sorbitol concentration. Also, two cathodic processes were observed, one (wave) associated with the hydrogen evolution reaction (HER) on 1010 steel, the other (peak) with zinc bulk reduction, simultaneous to the HER. Furthermore, the plating-process kinetics was controlled by mass transport. The presence of sorbitol in the bath led to formation of light-grey zinc films, even during the HER, without cracks and dendrites. Plating current efficiency decreased from $62% to 43% on increasing the sorbitol concentration in the plating bath. In the presence of 0.1 M ½Zn(OH) 4 2À and/or sorbitol concentrations higher than 0.2 M, Zn electrode dissolution was inhibited. However, a small dissolution of zinc electrode was observed with 0.05 M sorbitol in alkaline solution without zincate. SEM micrographs showed that the 1010 steel substrate was fully covered by Zn film and that the sorbitol affected the morphology of zinc films, acting as a grain refiner.

Study of the influence of the polyalcohol mannitol on zinc electrodeposition from an alkaline bath

“…3c), a peak a 1 is seen in the positive sweep at -1.48 V and -1.43 V, in the absence and presence of 0.20 M mannitol, respectively, which is due to zinc dissolution. Thus, mannitol appears to hinder zinc dissolution, probably by being adsorbed on the zinc electrodeposit, corroborating earlier results of Carlos and co-workers [11], who reported that zinc dissolution was inhibited in the presence of sorbitol.…”

“…Zinc has been electrodeposited from various alkaline solutions including zincate without additives [4] or with additives such as the following: C 6 F 13 C 2 H 4 (OC 2 H 4 ) 12 OH and C 12 H 25 (C 2 H 4 O) 12 H [5]; a tetraalkylammonium salt [6,7]; ammine-oxalate-EDTA [8]; tetramethylammonium, tetrabutylammonium or benzyl alcohol [9]; glycerol [10], and sorbitol [11]. Alkaline electrolytes are preferable not only from the point of view of environmental protection but also for their low corrosiveness, compared to acid electrolytes.…”

“…We have been studying the electrodeposition of zinc onto AISI 1010 steel from alkaline solutions containing various polyalcohol additives, since we noted that the presence of sorbitol or glycerol in an alkaline deposition bath has a beneficial effect on the quality of Zn [10,11], Pb [12], Sn [13], and Cu [14,15] electrodeposits. In these experiments, it has been established that the presence of sorbitol in the bath leads to the formation of light-gray zinc films, even during the evolution of hydrogen, without cracks or dendrites [11]; reduces the propagation of dendritic growth of lead, refining the lead deposit and allowing the new electrolytic solution to be used to recycle lead scrap [12]; works as a brightener, since tin crystallites were much smaller than those obtained from an alkaline solution without sorbitol [13], and leads to smaller-copper crystallites and a smoother copper film, with a golden color [14,15].…”

“…In these experiments, it has been established that the presence of sorbitol in the bath leads to the formation of light-gray zinc films, even during the evolution of hydrogen, without cracks or dendrites [11]; reduces the propagation of dendritic growth of lead, refining the lead deposit and allowing the new electrolytic solution to be used to recycle lead scrap [12]; works as a brightener, since tin crystallites were much smaller than those obtained from an alkaline solution without sorbitol [13], and leads to smaller-copper crystallites and a smoother copper film, with a golden color [14,15]. When glycerol was added to a zinc deposition bath, good values of current efficiency (CE) were observed and zinc deposits were adherent [10].…”

Voltammetric and morphological characterization of zinc electrodeposition from acid electrolytes containing boric–polyalcohol complexes

“…It can be inferred from these curves that this complex hinders zinc dissolution, since the anodic peak potential was shifted *50 mV in the positive direction in the presence of boricsorbitol complex. This result corroborates those obtained by Pereira et al [26] who report that Zn electrode Similar results were obtained at different E f (-1.35 V and -1.55 V). Also, it was noted that the voltammetric dissolution of zinc film produced in a plating bath containing glycerol was similar to that in the absence of additive (Fig.…”