Direct current electrodeposition of Zn-SiC nanocomposite coatings from citrate bath

Zn-SiC nanocomposite coatings are successfully produced by galvanostatic electrodeposition from aqueous citrate solutions, using SiC nanoparticles (NPs) with an average size of 56 nm. The optimal parameters of the zinc-citrate bath are chosen on the basis of analysis of a thermodynamic model. The effect of applied current density, bath composition, and hydrodynamic conditions are studied. The kinetics and mechanism of zinc reduction in the presence of SiC NPs are investigated using cyclic voltammetry. The surface charge of SiC NPs suspended in the electrolyte solutions is examined by the dynamic light scattering technique. The electrodeposited Zn-SiC coatings are characterized by wavelength dispersive X-ray fluorescence and scanning electron microscopy. It is shown that SiC codeposition with Zn proceeds through the entrapment of ceramic NPs during the reduction of citrate-zinc ions that are first adsorbed on the surface of the ceramic NPs. A maximal content of 6.4 wt% SiC incorporated into the Zn matrix is obtained at the lowest applied current density of j = –0.5 A dm^–2, with a nearly constant faradaic efficiency of 90%.