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 ZnSO4 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.
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