Corrosion mechanism of Zn-30Sn high-temperature, lead-free solder in neutral NaCl solution

Corrosion mechanism of Zn-30Sn high-temperature, lead-free solder in neutral 0.5 M NaCl solution are investigated by using FE-SEM, XRD, XPS and SIMS. The results confirm that α-Zn phases are corroded preferentially. Moreover, during initial corrosion process, a double-layer structure of ZnO and Zn(OH)2 is formed, providing beneficial barrier effect hindering the penetration of Cl−. However, subsequent morphology transformation weakens barrier effect to Cl− penetration and results in severe corrosion. Mechanism of surface layer breakdown and internal corrosion propagation are further examined, where it is determined that aggressive Cl− plays an important role in the corrosion process of Zn-30Sn solder.