Effect of Cl– and $${\text{SO}}_{4}^{{2 - }}$$ Ions on Electrodeposition of Cobalt from Acidic Gluconate Solutions

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

“…It is worth to note here that the presence of metal ions improves buffer capacities of the baths, but the component affecting predominantly the buffer capacity remains sodium gluconate. 21,29,30 Further potential scanning revealed higher cathodic currents below −1.2 V developing a peak C 1 at about −1.4 V followed by a cathodic branch C 2 . According to the CV curves for the single metal systems, the C 1 cathodic peak reflects primarily deposition of zinc with nickel, while the C 2 branch involves additionally incorporation of manganese accompanied by intense hydrogen evolution.…”

“…Previous studies have confirmed that gluconate solutions are much more resistant to pH changes than simple salt baths, especially when combined with sulfate ions. 21,29,30 Cyclic voltammetry.-Figure 2 shows a set of cyclic voltammograms for single and three-component systems registered in the gluconate baths containing chloride or/and sulfate ions. The individual metals exhibit specific behavior originated from their different nobility, deposition kinetics and hydrogen overpotentials.…”

“…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).…”