The oxidation of lead-free Sn alloys by electrochemical reduction analysis

The oxidation of pure tin and Sn-0.7Cu, Sn-3.5Ag, Sn-1Zn, and Sn-9Zn alloys at 150°C was investigated. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis by measuring the electrolytic reduction potential and total transferred electrical charges. X-ray photoelectron spectroscopy was also conducted to support the results of reduction analysis. The effect of copper, silver, and zinc addition on surface oxidation of tin alloys is reported. For tin, Sn-0.7Cu, and Sn-3.5Ag, SnO grew first and then the mixture of SnO and SnO2 was found. SnO2 grew predominantly during long-time aging. For zinc-containing tin alloys, both ZnO and SnO2 were formed. Zinc promotes the formation of SnO2.