Electrodeposition of Tin from Fluoroborate Bath onto Stainless Steel ۴۳۰ Substrate

In this study, first, the mechanism of recovery of tin from fluoroborate bath, a very suitable leaching agent in tin recovery, was obtained by cyclic voltammetry and chronoamperometry methods, and kinetic parameters were calculated. These techniques reveal that; i) tin reduction is a single-step and diffusion-controlled reaction, ii) initial nucleation is instantaneous, followed by typical three-dimensional (۳D) growth. The diffusion coefficient, number of active sites, and proton reduction rate constant are found to be ۱.۴۶ × ۱۰-۵ cm۲/s, ۸۰ ×۱۰-۵ (۱/cm۲), and ۲.۱۲× ۱۰-۶ mol/cm۲s, respectively. Subsequently, to find the optimal recovery conditions, solutions with different tin and fluoroboric acid concentrations were prepared, and different cathodic current densities were investigated. For each experiment, the cathodic efficiency was calculated, and the morphology of the deposits was obtained. The deposits were often spongy/dendritic with moderate adhesion to the substrate. The highest efficiency of ۹۰.۷۰% was obtained in tin concentration, fluoroboric acid concentration, and current density of ۴۰ g/L, ۱۷۰ g/L, ۲۰ mA/cm۲, respectively. While the addition of gelatin improved the morphology, the efficiency slightly decreased.

Keywords:

Tin , electrowinning , Fluoroboric acid electrolyte , cathodic efficiency.