A method of preparing a palladium-silver alloy gas separation membrane system, wherein the surface of the palladium layer or a silver layer is activated by a non-chemical activation method involving abrasion to a controlled surface roughness and abrasion pattern, thereby permitting the plating or deposition of an overlayer of silver on the palladium layer, silver on a silver layer, or palladium on a silver layer. The palladium and silver layers are preferably supported on a porous metal support to which an intermetallic diffusion barrier has been applied.