The thermal properties of Sn-Pb eutectic alloy doped with Ga, Te or Cu in different particle sizes have been investigated by DTA and XRD methods. It has been shown that SnO was formed on the surface of the eutectic particles doped by Ga at about 475 degrees C. In other cases, SnO2 was also observed. In larger particles, the oxidation occurred in multiple stages, while simple step occurred only on the smaller sized particles.