Codeposition of Zinc with Manganese from Different Gluconate Baths

Effect of Chloride and Sulfate Ions on Electrodeposition and Surface Properties of Alloys Produced from Zinc-Nickel-Manganese Gluconate Baths

“…The nucleation model in the ternary system is the same as for the binary Zn-Ni and Zn-Mn alloys deposited from gluconate baths. 22,23 It should be emphasizing that the nucleation step during the Zn-Ni-Mn codeposition has not been previously reported in the literature.…”

“…Particular fractions were calculated using stability constants of the individual species summarized in the earlier papers. [19][20][21][22][23] The assessment did not include boric acid and its complexes with the metal ions, since the acid exists in a molecular form at given pH, while the data on complexation reactions are tentative or uncertain. 27,28 However, it should be emphasized that a possible liability of the calculations can be caused by boric acid dissociating in the near-cathode solution layer that can turn more alkaline during high current electrolysis and thus leading to form various polyborate species as potential complexing ligands.…”

“…This was accompanied by higher oxygen percentages in the layers and reduced current efficiencies below −1.5 V. It indicates that the presence of manganese in the deposits is also a consequence of secondary processes, especially that Mn 2+ ions do not form complexes stable enough to protect against salt hydrolysis at potentials where hydrogen evolution is dominant and shown by the CV results. 22,31 The latter is especially noticeable in the chloride-containing baths having worse buffering properties than the sulfate bath 29,30 and containing manganese ions as free cations and cationic chloride complexes (Fig. 1).…”

“…23 Incorporation of manganese and/or its hydrolysis products changed the topography resulting in a development of columnar configurations with hierarchical structure comparable to these observed during codeposition of zinc with manganese. 22 It seems that with the deposition time, concentrations of the electroactive metal ions at the cathode surface decreased and become insufficient to supply fresh ions from a bulk electrolyte of high conductivity. This led to fast nucleation of the solid phase at the tops of the surface irregularities producing tiered structures consisting of fine grained crystallites.…”

“…Successful codeposition of binary Zn-Ni and Zn-Mn alloys as well as pure metals from various gluconate baths were reported in the previous papers. [19][20][21][22][23] Speciation of gluconate electrolytes containing chloride, sulfate or mixed metal salts has been shown to have a greater effect on morphology, wettability and corrosion properties for pure zinc than for pure nickel or binary alloys. On the other hand, the solution composition affected kinetics and mechanism of the electroreduction of the metal ions.…”