Zn Electrodeposition from an Acidic Chloride Bath Containing Polyethyleneglycol (Mw 200) and Benzylideneacetone as Additives

Abstract

The influence of Polyethylene Glycol 200 (PEG200) or a PEG200/benzylideneacetone (BDA) mixture on the mechanism of Zn deposition and nucleation kinetics was studied by voltammetry, chronoamperometry and atomic force microscopy (AFM). The addition of PEG200 or PEG200/BDA to the solution partially inhibited the reduction of Zn(II) at E =− 1.135 V vs. SCE. In the presence of PEG200/BDA, an additional reduction process was observed at E =− 1.24 V vs. SCE. Analysis of the nucleation processes indicated that, in all systems studied, the initial stage of Zn deposition was dominated by 3D diffusion-controlled nucleation. At E =− 1.132 V vs. SCE, the addition of PEG200 caused a reduction in the nucleation rate constant (A) and the number density of active sites (N0) with respect to the values obtained without additives. AFM analysis of coatings obtained at E =− 1.132 V vs. SCE, showed the formation of Zn clusters with different sizes distributed randomly on the surface. At E =− 1.243 V vs. SCE, both A and N0were higher for the solution containing the PEG200/BDA mixture than for the systems with PEG200 alone or without additives. AFM analysis revealed the formation of similarly sized Zn clusters uniformly distributed on the surface.