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

Abstract

Electrodeposition of ZnZr and ZnV oxide composites was performed under galvanostatic conditions at 313 K on unagitated pH 2 sulfate solutions containing Zn 2+ and Zr 4+ or VO 2+ ions and an additive such as polyethylene glycol (PEG). The effects of PEG addition on the codeposition 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 ZnZr solution in the absence of PEG was approximately zero, it increased significantly at a current density of above 1000 A•m ¹2 following the addition of PEG. In the ZnV solution, the V content in the deposits obtained from 100 to 2000 A•m ¹2 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 Zr 4+ and VO 2+ ions proceeded smoothly, resulting in an increase in the Zr and V content in the deposits. Additionally, the crystal platelets of Zn in the ZnZr and the ZnV 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 ZnZr and ZnV 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.

Micro Structure and Corrosion Resistance of Zn Composites Films Produced by Pulse Electrolysis from a Insoluble Particle-free Solution Containing Zr Ions

“…18,19) Therefore, when metal ions (M n + ) that hydrolyze at low pHs are added to electrolyte solutions as a second element, they turn into solid hydroxides or oxides via a hydrolysis reaction (M n + +nH 2 O→M(OH) n + nH + ) and codeposit with the deposited Zn films. [20][21][22][23][24][25][26][27][28][29][30] Thus, the hydrolysis reaction during electrodeposition facilitates composite electrodeposition, without the need for the addition of insoluble solid particles into the electrolyte.…”

“…However, Zn films with Zr hydroxide or oxide dispersed uniformly on the surface were not obtained. [25][26][27][28][29][30] This was attributed to the hydrolysis reaction of ZrO 2 + ions (ZrO 2 + + 3H 2 O → Zr(OH) 4 + 2H + or ZrO 2 + + H 2 O → ZrO 2 + 2H + ) proceeding partially on the Zn surface under electrolysis at a constant current density. If the hydrolysis reaction of ZrO 2 + ions occurs at the site of the hydrogen evolution reaction, the hydrolysis reaction of ZrO 2 + ions should proceed uniformly when the hydrogen evolution reaction occurs uniformly.…”

“…31) In the case of the deposited films obtained under constant-current electrolysis, when Zr hydroxide or oxide is codeposited with Zn, the reduction reaction of dissolved oxygen is suppressed on the deposited films. 29,30) The corrosion resistance of the Zn-Zr compound composite films appears to differ according to the codeposition state of the Zr compound.…”