Copper-nickel is an alloy primarily composed of copper and nickel, typically containing around 70% copper and 30% nickel. This combination gives the alloy excellent resistance to corrosion, making it suitable for marine applications, such as shipbuilding and underwater equipment. It also has good thermal and electrical conductivity. In addition to its practical uses, copper-nickel is often used in coinage, such as the United States nickel. The alloy's durability and resistance to tarnishing make it ideal for coins that need to withstand wear and tear over time. Its attractive appearance also contributes to its popularity in decorative items.