The effects of the addition of aluminum and natural aging on the tensile properties of Sn-9Zn and Sn-9Zn-0.5Al were investigated in rapidly solidified bulk specimens. Because oxidation occurs from the eutectic cell boundary of the surface and grows simultaneously into the subsurface with increased aging time, the deterioration of the tensile properties of Sn-9Zn and Sn-9Zn-0.5Al specimens correspond to the number of days it is naturally aged. The fracture characteristics of tensile fracture surface change from ductile dimples to partially dimpled and partially intergranular. The intergranular fracture behavior is attributed to the tensile cracks initiated from the surface cell boundary, cracks caused by cell boundary oxidation. This result indicates the depth of boundary oxidation that can be promoted by alloyed 0.5% aluminum.