Effect of relative humidity on corrosion behavior of SAC305 and Sn–37Pb solders under polyvinyl chloride fire smoke atmosphere

Abstract

The effect of ambient relative humidity from 50 to 98% on the corrosion characteristics of SAC305 and Sn–37Pb solders under the polyvinyl chloride fire smoke atmosphere was researched. The corrosion kinetics results reveal that the mass loss and corrosion rate of both solders show an increasing trend when the relative humidity is lower than 90%. While the mass loss and corrosion rate at 98% relative humidity present a significant decrease compared with those at 90% relative humidity, which may be ascribed to the impeded diffusion of oxygen under saturated humidity environment. The corrosion rate analysis indicates that SAC305 solder is more susceptible to corrosion. Besides, the corrosion microstructures reveal that the corrosion products grow more and more with the increase of relative humidity, but are most serious at 90% relative humidity. Sn21Cl16(OH)14O6 with SnO and SnO2 are detected as the main corrosion products of SAC305 solder by EDS, XRD and XPS analysis. While the corrosion products of Sn–37Pb solder are Sn21Cl16(OH)14O6 and PbCl2.