Influence of Chloride and Sulfate Ions on Electrodeposition, Wettability and Corrosion Resistance of Zinc Coatings Produced from Gluconate Solutions

Abstract

Electrodeposition of zinc from slightly acidic gluconate solutions was investigated. Cyclic voltammetric measurements showed inhibition of a cathodic process by sulfate ions. Chronoamperometric study combined with a speciation of individual solutions indicated instantaneous zinc nucleation interrupted by concurrent hydrogen coevolution and release of zinc cations from ZnSO 4 complexes. Morphology of coatings was strongly affected by deposition potentials and a type of zinc salt. Sulfate anions hindered zinc deposition, enhanced development of (100) crystallographic plane and increased cathodic current efficiency. In a presence of chloride ions, zinc growth toward bulk electrolyte and development of (002) crystallographic base plane of hexagonal structure were preferred. Water contact angles (WCA) of zinc deposited from chloride-containing baths revealed the highest values of 131-135°, while the highest WCAs of coatings obtained from sulfate bath reached only 112-119°. Moderately rough and hydrophobic as-plated zinc coatings were characterized by slightly improved corrosion resistance in both neutral and acid solutions.

Fast electrodeposition of zinc onto single zinc nanoparticles

“…− 1.2 V vs. SCE, in agreement with that of the literature [10]. The rather flat cathodic current observed for potentials more negative than − 1.25 V vs. SCE is related to the continuous deposition of zinc from the solution onto the electrode surface, and in a smaller extent to the hydrogen reduction, whose overpotential is high at carbon as well as zinc substrates [10,45,46]. Upon oxidation, two typical crossover points between the anodic and the cathodic branches of the cyclic voltammetry can be observed at potentials of c.a.…”

“…− 1.22 V and of − 1.1 V vs. SCE. The crossover point observed at more cathodic potentials (in this case − 1.22 V vs. SCE) is usually ascribed to the nucleation of the new phase formed upon the zinc deposition [45]. Proceeding along the anodic branch of the voltammetry, the metallic zinc previously deposited onto the carbon microelectrode is oxidised at a potential of c.a.…”

“…The smaller amount of reductive charge (and consequently the smaller amount of zinc deposited onto the Zn NPs) recorded during the collision experiments in the supported solutions containing 10 mM and 100 mM K 2 SO 4 can be explained considering two effects: (I) a higher charge screening effect of the supporting electrolyte towards the Zn NPs and (II) a higher amount of SO 4 2− anions in solution. Sulphate ions tend to hinder the zinc deposition reaction, because of the occurrence of a strong ion pairing between the Zn 2+ cations and the SO 4 2− anions; stable sulphate complexes are thus formed, with a consequent hindered release of the Zn 2+ cations, leading to a lower concentration of free Zn 2+ in solution [45,50].…”

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

“…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.…”

“…The latter are particularly interesting from the viewpoint of correlations among composition, morphology, wettability and corrosion resistance of the deposits. (Super)hydrophobic surfaces represent a recent trend in the progress of innovative z E-mail: erudnik@agh.edu.pl sacrificial coatings, 24,25 but this topic has not yet been studied for electrodeposited ternary Zn-Ni-Mn alloys.…”