Electrochemical nucleation and growth of Sn onto double reduction steel substrate from a stannous fluoborate acid bath

Cyclic voltammetry (CV), chronoamperometry (CHR) in conjunction with scanning electron microscopy (SEM) technique have been performed to study the electrodeposition behavior of tin onto double reduction steel substrate from a stannous fluoborate acid bath. Results show that, under the experimental conditions, the initial reduction process of tin is controlled by diffusion and follows the three-dimensional (3D) nucleation and subsequent grain growth mechanism. With the increase of the applied cathodic overpotentials, the nucleation type of tin changes from progressive mechanism to instantaneous mechanism. When the deposition overpotential is high, the electrode surface is fully covered with tin deposits in short times that the current-time transient is composed of the tin nucleation current and the current attributed to proton reduction on the tin growth centers while the current due to proton reduction on the steel surface should be considered as well at low deposition overpotentials. Results also reveal that both the tin nucleation and proton reduction rate constant increase with increasing the cathodic overpotentials, and the proton reduction rate constant on the steel substrate surface is larger than that on the tin growth centers. The diffusion coefficient of tin species is found to be 1.24E−5 cm2 s−1.