Hybrid composites were prepared using insert injection molding without preheating. Thermoplastic elastomer (TPE) was overmolded on etched aluminum sheets having porous surface to provide large contact area between insert and TPE. The resulting bond strength was studied using a 180 degrees peel test. The effect of aluminum microstructure and various processing steps of the surface treatment procedures on adhesion were studied. Maximum peel strength obtained was 9.33 N/cm using P2 treatment with alkaline-acid pretreatment. Lowest peel strength of 1.68 N/cm was achieved by alkaline-acid treatment. Increasing insert thickness lowers the peel strength since large heat capacity of thicker insert cools the melt and limits penetration of the melt to insert microcavities. At certain insert thickness microcavities are impregnated by the melt and no additional effect can be obtained by decreasing the