Brass is commonly used for making connectors. Brass has a combination of strength, ductility and low electrical resistance that makes it an excellent choice for connector construction. Phosphor bronze is sometimes used instead of brass on connectors that require a strong, elastic metal. Phosphor bronze is often used in connectors with spring contacts. Phosphor bronze, brass and copper are all typically coated to prevent corrosion. Nickel is the most common connector coating. Gold is sometimes used when higher electrical performance is required, such as high speed data transmission. Tin is often used to coat exposed copper wires to prevent corrosion, fraying and ease soldering.