Corrosion process study of Zn-30Sn high-temperature lead-free solder

The corrosion process of Zn-30Sn high-temperature solder alloy was investigated in neutral 0.5 M NaCl solution at room temperature (25 ± 0.5 °C) by Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The surface observation by SEM indicates that the surface morphology of Zn-30Sn evolves from the dense particle structure to porous structure, and finally converts to platelet-like structure. Energy Dispersive X-ray Analysis (EDXA) shows that Zn phase is corroded preferentially due to no Sn compound was observed. The outer surface of corrosion product was confirmed as Zn(OH)₂ by XPS. Dominant corrosion products were characterized as a mixture of ZnO, Zn(OH)₂ and Zn₅(OH)₈Cl₂·H₂O. The corrosion process was further discussed in detail.