Direct Current Electrodeposition of Zn-SiC Nanocomposite Coatings from Citrate Bath

Abstract

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%.

The Effect of Direct and Pulsed Current in the Presence of Surfactants on the Electrodeposition of Zn–SiC Nanocomposite Coatings

“…Citrates also provide the stabilization of the pH of electrolyte solutions, hence they are widely used in the electrodeposition of zinc and its alloys [55,56]. The electrolyte composition in this work was selected based on earlier studies of the electrodeposition of zinc-based alloys from aqueous citrate solutions [53,54,[56][57][58][59]. The only variable in the bath chemistry was the type of organic additive ( Figure 1).…”

“…Analysis was carried out using a Rigaku Primini spectrofluorimeter (Rigaku, Tokyo, Japan) with scintillation counters (LiF crystal). The weight percentage of SiC in the Zn-SiC composite was calculated from the Zn and Si weight percentages, as described elsewhere [27,53,54], assuming that all Si atoms are bound to C as SiC in a 1:1 molar ratio. The faradaic efficiency (FE) of the process was calculated, as described elsewhere [53,54], assuming that only zinc ions could be deposited on the cathode.…”

“…The optimal parameters of the zinc-citrate bath were chosen on the basis of the analysis of a thermodynamic model. The effect of the applied current density, bath composition, and hydrodynamic conditions were studied [53]. Zeta potential measurements confirmed the adsorption of citrate and citrate-zinc ions as well as gelatin molecules on the surface of the SiC NPs.…”

“…Previously we investigated, for the first time, the DC co-deposition of Zn-SiC from aqueous citrate bath with gelatin as a bath additive [53,54]. The optimal parameters of the zinc-citrate bath were chosen on the basis of the analysis of a thermodynamic model.…”

“…Zeta potential measurements confirmed the adsorption of citrate and citrate-zinc ions as well as gelatin molecules on the surface of the SiC NPs. It was shown that SiC co-deposition with Zn proceeds through the entrapment of ceramic NPs during the reduction of citrate-zinc ions firstly adsorbed on their surface as well as by the mechanical entrapment of NPs agglomerates in the cavities formed in the Zn deposit [53,54].…”