ELECTROLESS DEPOSITION OF PURE NICKEL, PALLADIUM AND PLATINUM

Electroless deposition techniques are used for an increasing number of applications where thin metallic coating of complex shaped components is required. However, in most cases, the deposits obtained are not composed of pure metals but rather contaminated with undesirable elements released during the plating process (phosphorus, boron, sulphur, heavy metals). For specific applications involving a high temperature environment or requiring ductile coatings, electroless deposition of pure metals is necessary. For this purpose, a new process was designed using hydrazine as the reducing agent. Electrochemical measurements throughout a wide range of bath compositions were performed; several specific compositions were selected which provide high purity deposits of metals such as nickel, palladium and platinum. Attempts to rationalize the deposition processes in terms of electrochemical reactions are briefly reported. The optimization of several bath formulations is being discussed. Some physical and chemical characteristics of the pure metal deposits obtained are compared with those of classical electroless metallic coatings.