SIMULTANEOUS DEPOSITION OF PD AND AG ON POROUS STAINLESS-STEEL BY ELECTROLESS PLATING

This work investigates the codeposition behavior of palladium and silver on porous stainless steel by means of electroless plating. Although palladium and silver can be deposited independently to a considerable thickness, simultaneous deposition of palladium and silver is passivated by the preferential deposition of silver in an electroless bath containing EDTA as a complexing agent. After effective activation of the substrate by Pd predeposition, Pd and Ag can be successfully codeposited. A combination of XRD and EDX analyses reveals that codeposited Pd and Ag are in separate phases and that small amounts of an amorphous palladium rich phase are also present in the deposited material. Thus a codeposition mechanism of Pd and Ag is proposed. Thermal treatment of as-deposited Pd-Ag films in H-2 atmosphere provides composite Pd-Ag alloy membranes on the porous stainless steel substrate.