Where should I use nickel-plated copper conductor? Underwriter's Laboratories has performed extensive life cycle testing upon a myriad of electrical apparatus and wiring materials. UL recommends that for conductors composed of strands 0.015-inches in diameter or smaller, silver- or nickel-plated copper strands should be used. This is to prevent the oxidation of the metallic surface of the copper strands composing the conductor. UL has observed that very fine strands of copper are more prone to damage resulting from this type of corrosion. The choice of nickel as a plating material is an obvious one. Nickel is known to be far more resistant to accelerated oxidation that occurs with many metals at elevated temperatures. It also has a much higher melting point (roughly twice that of copper), which provides structural support to a plated conductor subjected to extreme temperatures. In combination with the copper substrate, nickel provides an electrical conductor that exhibits only slightly higher resistivity, is flexible and resists fatigue. The use of nickel-plated copper conductors becomes very important at temperatures of 250 C, where 2% plating by weight is generally sufficient. For temperatures of 450 C and above, thicker plating is recommended, with 27% plating most commonly used in the United States. For temperatures exceeding 600 C, particularly in applications where the temperatures are alternatively high and then low, a pure nickel conductor may be required. One applications tool that nickel-plated conductors provide is a greater allowable ampacity than for a similar size copper conductor. Assuming all the cables in a conduit, raceway or cable tray have similar ratings for insulation temperature, a nickel-plated conductor may offer significant diameter or space-saving advantages. For details concerning allowable ampacities for both nickel-plated copper and copper conductors, consult The National Electrical Code, Article 310, Tables 310-18 and 310-19.