The stability of composite palladium membranes is of key importance for their application in hydrogen energy systems. Most of these membranes are prepared by electroless plating, and beforehand the substrate surface is activated by a SnCl2-PdCl2 process, but this process leads to a residue of Sn, which has been reported to be harmful to the membrane stability. In this work, the Pd/Al2O3 membranes were prepared by electroless plating after the SnCl2-PdCl2 process. The amount of Sn residue was adjusted by the SnCl2 concentration, activation times and additional Sn(OH)(2) coating. The surface morphology, cross-sectional structure and elemental composition were analyzed by scanning electron microscopy (SEM), metallography and energy dispersive spectroscopy (EDS), respectively. Hydrogen permeation stability of the prepared palladium membranes were tested at 450-600 degrees C for 400 h. It was found that the higher SnCl2 concentration and activation times enlarged the Sn residue amount and led to a lower initial selectivity but a better membrane stability. Moreover, the additional Sn(OH)(2) coating on the Al2O3 substrate surface also greatly improved the membrane selectivity and stability. Therefore, it can be concluded that the Sn residue from the SnCl2-PdCl2 process cannot be a main factor for the stability of the composite palladium membranes at high temperatures. (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.