White copper is a family of copper alloys that contain nickel, giving them a silvery-white appearance instead of copper’s familiar reddish tone. The term covers two closely related materials: cupronickel (copper plus nickel) and nickel silver (copper plus nickel plus zinc). Both have been used for centuries in everything from Chinese furniture hardware to modern coins and marine engineering.
Why Copper Turns White
Pure copper is reddish-orange. Add nickel, and the color shifts dramatically toward silver. Even a small percentage of nickel, around 5 to 10%, is enough to give the alloy a bright, silvery luster. Higher nickel content pushes the appearance closer to actual silver, which is exactly why these alloys have been used as silver substitutes for hundreds of years.
The two main types differ in one ingredient: zinc. Cupronickel is simply copper and nickel, typically in a 90/10 or 75/25 ratio. Nickel silver adds zinc to the mix, with a common formulation of 60% copper, 20% nickel, and 20% zinc. Despite the name “nickel silver,” neither alloy contains any actual silver. The name refers purely to color.
A Chinese Alloy With a Long History
White copper originated in China. The earliest known reference to “baitong” (白铜, literally “white copper”) appears in a Chinese dictionary from the 3rd century A.D., though it’s unclear whether that entry described a nickel-containing alloy or simply a pale copper variant. A more definitive reference comes from the 4th century, when a regional history recorded white copper production in Tanglang county. This appears to be the earliest documented mention of a true copper-nickel alloy.
For centuries, Chinese craftsmen used white copper (known in the West as “paktong,” from the Cantonese pronunciation of 白铜) to make furniture hardware, decorative fittings, and household objects. Paktong hardware was prized for reinforcement and decoration on classical Chinese furniture because the nickel content gave it a silvery shine and slowed the tarnishing that plagues ordinary brass.
Large quantities of paktong shipped out of Canton reached Europe, where the alloy fascinated scientists and metalworkers. In 1754, the Swedish chemist Axel Fredrik Cronstedt identified nickel as a distinct element. Two decades later, Gustav von Engeström analyzed a sample of Chinese paktong and confirmed it contained this newly discovered metal. By around 1824, the German manufacturer Ernst August Geitner had begun producing a European version commercially under the trade name “Argentan,” launching what became widely known as German silver.
Where White Copper Shows Up Today
You’ve almost certainly handled white copper without knowing it. The U.S. five-cent coin (the “nickel”) is 75% copper and 25% nickel. The 1- and 2-euro coins also use copper-nickel in their silver-colored portions. The alloy is ideal for coinage because it’s hard-wearing, resistant to corrosion, and easy to distinguish by color from other denominations.
The biggest industrial consumer of white copper is the marine sector. Copper-nickel’s resistance to both saltwater corrosion and biofouling (the buildup of barnacles and algae) makes it valuable in ways few other metals can match:
- Boat and ship hulls: Solid copper-nickel plate or copper-nickel cladding over steel keeps hulls cleaner longer, reducing drag and maintenance.
- Shipboard piping: Seawater cooling systems, bilge and ballast lines, fire-fighting systems, and sanitary piping all commonly use copper-nickel tubing.
- Desalination plants: In multi-stage flash and multiple-effect distillation facilities, copper-nickel tubing handles the heat exchange and brine contact that would corrode most other metals.
- Offshore oil and gas: Platforms and floating production vessels use copper-nickel alloy systems for seawater handling and splash-zone sheathing.
- Power plants: Steam turbine condensers, oil coolers, and auxiliary cooling systems at both nuclear and fossil fuel plants rely on copper-nickel pipes to handle seawater, brackish water, and freshwater.
Marine renewable energy is a growing application as well, with copper-nickel components finding use in offshore wind farms and tidal energy devices. Beyond the ocean, the alloy serves in cryogenic equipment, where its mechanical properties hold up at extremely low temperatures.
Nickel Silver in Everyday Objects
Nickel silver (the zinc-containing version) appears in a wide range of consumer products. Musical instruments like flutes, saxophones, and some guitar frets use it for its workability and bright tone. Flatware and serving pieces marketed as “silver plate” often have a nickel silver base underneath a thin layer of real silver. Zippers, eyeglass frames, keys, and decorative hardware frequently contain nickel silver as well.
For antique collectors, paktong is a material worth recognizing. Chinese furniture from the last several centuries often features paktong fittings: corner brackets, drawer pulls, lock plates, and hinges with a distinctive silvery color that ages differently from brass. Authentic paktong hardware typically contains 5 to 10% nickel and resists tarnish much better than plain brass, which can help distinguish original fittings from later replacements.
Nickel Allergy and Skin Contact
The one significant health concern with white copper is nickel sensitivity. Nickel allergy is one of the most common causes of contact dermatitis, and both cupronickel and nickel silver can trigger reactions in sensitive individuals. Symptoms typically include an itchy rash, bumps, skin discoloration, and in more severe cases, blistering or cracked, leathery skin at the point of contact.
Jewelry is the most frequent culprit. Rings, bracelets, necklaces, watch cases, and piercing jewelry made from nickel silver can cause persistent skin irritation if worn for extended periods. Kitchen utensils, metal tools, and even coins can also be sources of exposure. People who work regularly with nickel-containing metals face a higher risk of developing the allergy over time. If you know you’re nickel-sensitive, look for jewelry labeled nickel-free or made from surgical stainless steel, titanium, or solid gold.
How to Tell White Copper From Silver
White copper alloys look convincingly like silver at first glance, which is the whole point. A few differences help tell them apart. Real silver is softer and tarnishes to a dark, almost black patina over time. White copper tarnishes more slowly and tends to develop a yellowish or greenish tone rather than black. Silver is also noticeably heavier. A hallmark or stamp (like “925” for sterling silver) is the most reliable indicator, since nickel silver items are sometimes stamped “NS,” “EPNS” (electroplated nickel silver), or simply left unmarked.
If you’re examining an antique and suspect paktong, a subtle greenish tinge in areas of wear or corrosion is a strong clue. Silver corrodes to black; copper alloys corrode toward green. The weight, the color of the corrosion, and the absence of silver hallmarks together make identification fairly straightforward.