Effect of Polyethylene Glycol on Electrodeposition of Zn Active Metal Oxide Composites from a Particle-Free Solution

Abstract

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

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 84 (2020) 50–57.

Fig. 1 Zr and V content in deposits obtained at various current densities in (a) Zn–Zr and (b) Zn–V solutions with and without PEG (○ without PEG, ● with PEG).