Effect of process parameters on the electrodeposition of zinc on 1010 Steel: Central composite design optimization

Abstract

In the present work, we studied the effect of critical electrogalvanizing parameters on the quality of electrodeposited Zn films. The current density, electrodeposition time, and ZnCl2 concentration of electrolyte were optimized to maximize current efficiency and brightness, and also, to minimize the surface roughness. Importantly, regression models of the response variables were developed. These models could help industrial applications by providing definitive process conditions to obtain Zn coatings at a desired thickness, roughness and brightness with a high current efficiency. First, preliminary studies were conducted to determine the initial levels of the designated factors. Then, the optimization was conducted through the Central Composite Design by Design-Expert (trial version). Upon completion of the optimization, analysis of variance was also performed. The optimum values of current density, coating duration and ZnCl2 concentration were determined as 3.7 A/dm2, 4.4 minutes, and 50 g/L, respectively, at a thickness of 6 m. Finally, a set of Zn films were deposited at this optimum conditions. The characterization of these films showed that the experimental results were in good accordance with model predictions, providing a bright (L=83.69) and smooth (Ra=0.75 μm) coating with excellent adhesion to steel substrate (pull-off strength > 29.4 MPa) at a current efficiency of 98.7%.