Phosphor bronze is a member of the family of copper alloys. It is composed of copper that is alloyed with 0.5–11% of tin and 0.01–0.35% phosphorus, and may contain other elements to confer specific properties (e.g. lead at 0.5–3.0% to form free-machining phosphor bronze). Alloyed tin increases the corrosion resistance and strength of copper, while phosphorus increases its wear resistance and stiffness.