OXIDATION OF NICKEL AND NICKEL-GOLD ALLOYS IN AIR AT 50-DEGREES-C-150-DEGREES-C

Analysis of the growth of the oxide film formed on nickel and nickelgold alloys at moderately low temperatures (50°-150oC) in a typical laboratory air environment has been carried out. Film thicknesses and growth rates were evaluated using Auger electron spectroscopy and contact resistance probing. Results conform to the concept of a limiting oxide thickness on nickel, which is no thicker than about 10A for the testing environment used. Results also suggest that an oxide of similar composition and limiting thickness is formed on the gold-nickel alloys. At temperatures under about 100°C, the oxide thickness is essentially temperature independent, is limited to the order of several monolayers, and has a contact resistance level near 100 mΩ for the probing conditions used. A model, comparing the alloy oxidation to the processes which are hypothesized to occur in a gold over nickel substrate system, is presented and estimates of time to reach specific contact resistance levels as a function of temperature and nickel concentration are given. © 1979, The Electrochemical Society, Inc. All rights reserved.