Palladium composite membranes on porous stainless steel were prepared by electroless plating. In order to obtain a thin palladium film, an intermediate layer was necessary to modify the pore size of the substrate and form a diffusion barrier between the palladium film and the support. The NaA zeolite, used as intermediate, was synthesized by vacuum-assisted secondary growth. Pure gas permeability tests were conducted using hydrogen and nitrogen between 400 and 450 degrees C. The Surface morphology and the components of the different layers of the membrane were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). When vacuum Was applied during the zeolite synthesis at 80, C, the Pd membrane showed high H-2/N-2 ideal selectivity in the working temperature range. This result suggests that NaA zeolite is an effective intermediate Substrate modifier when an appropriate synthesis method is employed. (C) 2009 Elsevier B.V. All rights reserved.