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, which makes it useful in various industrial applications. In addition to its practical uses, copper-nickel is often employed in coinage, with countries like the United States and Australia using it for their coins. The alloy's durability and resistance to tarnishing make it an ideal choice for coins that need to withstand wear and tear over time.