The corrosion behaviors of Sn-20Bi-xCu-yIn (x=0.3, 0.5 wt.%; y=1, 2, 3 wt.%) in 3.5 wt.% NaCl solution at room temperature were investigated. Electrochemical impedance spectroscopy (EIS) plots, potentiodynamic polarization curves, and corroded surface product characterization were used to evaluate the corrosion resistance of the solders. Analysis of EIS and polarization curves shows that the corrosion resistance of the solders decreases as the In and Cu contents increase. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were applied to characterizing the corrosion product. It is found that the corrosion product is Sn₃O(OH)₂Cl₂, which cannot play a protective role because of its loose structure. Sn-20Bi-0.3Cu-1In has the best corrosion resistance.