Effect of polyethylene glycol on electrodeposition of Zn active metal oxide composites from a particle-free solution

Electrodeposition of Zn-Zr oxide and Zn-V oxide composites was performed under galvanostatic conditions from an unagitated sulfate solution containing Zn²⁺, Zr⁴⁺, or VO²⁺ ions and an additive such as polyethylene glycol (PEG). The sulfate solution had a pH of 2 and the electrodeposition was performed at 313 K. The effects of PEG on the co-deposition of the Zr oxides and V oxides and their polarization behavior were investigated. Additionally, the effects of PEG on the microstructure of the deposits were investigated. Although the Zr content in the deposits obtained from the Zn-Zr solution without PEG was approximately zero, it increased significantly at a current density above 1000 A m- following the addition of PEG. In the Zn-V solution, the V content in the deposits obtained from 100 A m-2 to 2000 A m-2 was higher with PEG than that without PEG. In the presence of PEG, the cathode potential polarized, the rate of hydrogen evolution increased, and the hydrolysis reaction of Zr⁴⁺ and VO²⁺ ions occurred easily. This resulted in the Zr content and V content increasing in the deposits. Additionally, the crystal platelets of Zn in the Zn-Zr oxide film and the Zn-V oxide film became fine, and the surface coverage of the spongiform Zr oxide and the film-like V oxide increased. Furthermore, the corrosion current densities of the Zn-Zr oxide film and the Zn-V oxide film obtained from the solution with PEG were lower than those from the solution without PEG. The reduction reaction of dissolved oxygen decreased in the films with PEG, thereby decreasing the corrosion current density.