CORROSION OF ELECTROLESS NICKEL PLATED ELECTRICAL CONTACTS

Electroless nickel plating has been tried on steel and brass substrates for potential use as low power electrical contacts and connectors. By selected conditions of heat treatment in a high vacuum environment the plating can produce chromium equivalent hardness without the effluents of the hard chromium plating process. The resulting surfaces were examined and characterized under an optical and a scanning electron microscope. XRD analysis was also performed to investigate re-crystallization effects, especially after heat treatment. The fabricated contact materials were also tested under corrosion conditions and linear polarization measurements were performed on them. Finally, to indicate the significance of the substrate material, semispherical nickel plated brass and steel joints were tested under the simultaneous application of a mechanical and an electrical contact load exceeding 10,000 duty cycles. The contact resistance was also monitored during the computer controlled contact make-break operations. The results show that, after heat treatment in a high vacuum environment (10(-6) mbar), the plating acquires a crystalline structure, with very good adhesion to the substrate material. In addition it is characterized with good electrical properties during corrosion aging accelerated tests.