Effect of bismuth addition on the corrosion dynamics of Sn–3Ag–0.5Cu solder alloy in Hydrochloric Acid Solution
Abstract
This paper aims to investigate the effect of bismuth addition on the corrosion behaviour of Sn–3.0Ag–0.5Cu (SAC 305) solder alloy in 1M HCl acid solution under potentiodynamic polarization. After electrochemical tests, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to examine the properties of the samples. Polarization studies indicated that an addition of 0.5, 1, and 2 wt.% Bi in the SAC305 solder alloy doesn't lead to significantly different corrosion potentials. Instead of a true passivation region, a pseudo-passivation region is observed in which currents are nearly constant (though high). This pseudo-passive region does not have a reactivation point within the scanning interval. Corrosion rates, on the other hand, follow a pattern in which 1 wt.% bismuth replacement of silver causes a drop-in corrosion rate. With the further replacement of silver with bismuth, however, the corrosion rate increases. Microstructure analysis reveals the existence of gaps and porosities which introduce limits on the formation and stability of protective passive corrosion products.
Keywords
Bi addition, Corrosion, Pb-free solder alloys, Microstructure
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