Pure copper, in its unoxidized state, exhibits a distinct reddish-orange or pinkish hue. This contrasts sharply with the silvery-white appearance often associated with the term “white copper.” Therefore, pure copper itself is not white. When people refer to “white copper,” they are describing specific copper alloys that have been engineered to possess a white or silvery color.
Understanding “White Copper”
The term “white copper” is commonly used to describe copper-based alloys that do not display copper’s characteristic reddish color. These alloys achieve their silvery-white appearance through the addition of other metals. The presence of these alloying elements alters the metallic structure and light reflection properties, resulting in a color that can resemble silver. Historically, naturally occurring copper-nickel ores were smelted by ancient civilizations, leading to some of the earliest forms of what was called “white copper” or “paktong.”
Key Alloys Mistaken for White Copper
Two primary copper alloys are frequently referred to as “white copper” due to their silvery appearance: cupronickel and nickel silver. Cupronickel is an alloy primarily composed of copper and nickel. Its copper content ranges from 60 to 90 percent, with nickel making up the remainder. Despite its high copper content, cupronickel exhibits a silver color, which becomes more pronounced with higher nickel percentages. This alloy is valued for its excellent resistance to corrosion, particularly in saltwater environments, and its good strength and ductility.
Nickel silver, also known as German silver, is another prominent “white copper” alloy. This alloy is a combination of copper, nickel, and zinc, and despite its name, it contains no actual silver. The composition of nickel silver varies, typically containing copper, nickel, and zinc. The addition of nickel and zinc gives nickel silver its characteristic silvery-white luster. This alloy is recognized for its good mechanical properties, including hardness and strength, and its resistance to corrosion, although it can tarnish slowly when exposed to sulfur in the air.
Where White Copper Alloys Are Used
Cupronickel alloys are widely utilized across various industries, particularly those involving marine environments. Their resistance to saltwater corrosion makes them suitable for piping, heat exchangers, and condensers in seawater systems, as well as for marine hardware like propellers and boat hulls. Additionally, cupronickel is a common material for coinage due to its durability, long service life, and resistance to tarnishing. For example, many modern coins, including the US nickel, are made from cupronickel.
Nickel silver finds extensive application where a silver-like appearance is desired without the cost of real silver. It is commonly used as a base metal for electroplated silverware and decorative items. Its properties, such as strength and workability, also make it a material of choice for musical instruments, including flutes and trumpets, and for components in electrical and telecommunication relays. Nickel silver is also employed in plumbing fixtures, architectural metalwork, and some food and chemical equipment due to its corrosion resistance.