Alloy 510 Phosphor bronze is one of the most popular copper-base alloys used in spring making, because it provides both corrosion resistance and electrical conductivity. Gibbs Interwire stocks Grade “A” (95% copper, 4.75″ tin, 0.25% phosphorus) spring wire, 8 numbers hard. Wire is available in size ranges from 0.0254″ – 0.125″