WATER CONTAMINATION - IMPACT OF TIN-LEAD SOLDER

A laboratory-scale leaching study with 50/50 Sn/Pb-soldered copper coupons showed the potential for water contamination. Significant leaching of Pb and Sn occurred from the Sn/Pb solder into high-purity, tap, treated and well water samples. The amounts of Cu and Zn released from soldered copper coupons were generally lower than those released from non-soldered copper coupons. No significant leaching of Cd occurred from the solder into the water samples. Optical micrographs of the exposed coupons showed evidence of corrosion, especially in the case of treated and well water samples. Further examination using electron microprobe and X-ray electron spectroscopic techniques showed the presence of lead and tin oxides on the Sn/Pb solder surface confirming the occurrence of galvanic corrosion. Transmission electron microscopy equipped with energy dispersive X-ray analysis unit showed the presence of Pb, S and Sn on the surface of samples exposed to well water. Therefore, it can be surmised that the surface is covered with Pb and Sn oxides, possibly accompanied by small amounts of sulphur species of lead.