Effects of Sn concentration and current density on Sn-Bi electrodeposition in additive free plating bath

Sn-Bi alloys were electroplated from sulphuric acid based plating baths containing tin sulfate (SnSO₄) and bismuth nitrate (Bi(NO₃)₃). The electrochemical behavior of the plating bath was investigated by electrochemical studies. Potentiodynamic polarization curves of the plating bath revealed the large potential gap between the two elements. The effects of SnSO₄ concentration and current density on the composition and morphology of the Sn-Bi electrodeposition were investigated. The surface morphology and composition of the Sn-Bi electrodeposited were investigated by scanning electron microscopic (SEM) coupled with energy dispersive X-ray (EDS) spectroscopic. The Sn content in the deposits increased with increasing of Sn content in the bath. Bi content was found to decrease with increasing current density because of the more noble deposition potential of Bi. The microstructure and surface morphology of the Sn-Bi electrodeposits become finer and smoother with increasing Sn content in bath but rougher and less compact when current density is increased. Sn-36.47 wt.% Bi alloy was fabricated from this additive free plating bath.