Electrochemistry Study of Additives Effect on a Zinc Electroplating Bath

CECILIA DANIELA COSTA; VIRGINIA DIZ; GRACIELA ALICIA GONZÁLEZ

PORTUGALIAE ELECTROCHIMICA ACTA

The Portuguese Electrochemical Society Journal

Año: 2023

0872-1904

This work presents a set of electrochemical techniques applied to investigate the effect ofadditives in baths for coating steel surfaces with Zn by the electroplating process. Theform and intensity of the reduction current were analyzed as a function of the appliedvoltage using linear sweep voltammetry (LSV). In this way, the different stages of theelectroplating process implicated in Zn deposition and the effect of each additive wereidentified. First, commercial additives, with highly complex composition, produced by alocal company, were studied with the aim of understanding their concentration effects onthe different stages of Zn electroplating process. Based on the capacity to emulate thoseresults, benzoic acid, previously reported as a brightener, and Triton X-100, as a leveler,were proposed as a simpler additive mix. Very strong synergistic effects were present,even in this simplified bath. The effect of different additives percentages on grain size ormorphology was also evaluated using scanning electron microscopy (SEM) images in thefinal stage. It was established a correspondence between the optimal concentration of thecommercial additive and a proposed bath with concentrations of 1-2 M Triton X-100 and3-9 M benzoic acid. Finally, electrochemical impedance spectroscopy (EIS) experimentswere carried out for the different bath compositions with this simplified additive mix. Theresults were interpreted through an equivalent electrical circuit represented by chargetransfer resistance (Rct,) in parallel with two constant phase elements (CPE) in parallel,which evidenced the deposit inhomogeneities.