a composite rigid foam structure that has a skin or coating on at least one of its surfaces . the skin is formed in situ by thermal spray techniques . the skin is bonded substantially throughout the surface of the porous substrate to the peripheries of the pores . the skin on the average does not penetrate the surface of the substrate by more than the depth of about 2 to 5 pores . thus , thermal spraying the skin onto the rigid foam produces a composite that is tightly and uniformly bonded together without unduly increasing the weight of the composite structure . both thermal conductivity and bonding are excellent .