What are the three simplest characteristics of white copper?

White copper is a copper-based alloy with nickel as the primary additive. Its three core characteristics are a silvery-white metallic luster, a nickel-copper alloy composition, and excellent corrosion resistance. It is widely used in both industrial and residential applications.

White copper ranges from silvery-white to grayish-white. When the nickel content exceeds 16%, it exhibits a pure white luster, and at 25%, it achieves a near-mirror finish. Its color stems from a single-phase structure formed by the uniform solid solution of nickel atoms, creating a stark contrast to the warm golden color of brass and the cool luster of silver. After long-term oxidation, silver forms a black sulfide layer on its surface, while white copper develops a bluish-gray or green rust that cannot be restored by wiping. Common identification methods can be used to distinguish the materials by weighing them (silver is denser) or listening to their sound (silver has a dull sound, while white copper has a crisper sound).

Typical white copper contains 60%-90% copper and 10%-30% nickel. The solid solution strengthening of nickel significantly enhances the material's properties. Different nickel contents cater to diverse applications: B10 white copper (approximately 10% nickel) is used for ship piping, while C77310 white copper (15%-20% nickel) uses zinc to reduce costs, making it a preferred choice for decorative applications. Their machining characteristics differ significantly: C70600 white copper with a 15% nickel content requires a low feed rate and carbide tools, otherwise it can easily harden and cause chipping. When the nickel content exceeds 20%, turning requires controlling the spindle speed below 35 ft/min and using forced cooling to prevent surface flaking. The segmented pulse tapping process effectively solves the problem of metal flow during deep hole machining.

Nickel forms a dense oxide film on the alloy surface, blocking corrosive media such as chloride ions. B30 white copper exhibits an annual corrosion rate of only 0.0028 mm in a 3.5% sodium chloride solution, far lower than the 0.05 mm of ordinary brass. It is widely used in marine engineering applications, such as offshore wind turbine fasteners and nuclear power plant heat exchangers. Deep-sea exploration has revealed that the passivation film integrity of a special type of nickel silver remains at 92.7% even at pressures exceeding 10,000 meters. After five years of service in the high humidity and heat of the South China Sea, a ship's nickel silver propeller requires only ultrasonic rust removal to restore its luster, surpassing stainless steel. Using gradient composite coating technology in polar environments, nickel silver components retain 98% of their tensile strength at 60°C. This technology has been used on the Xuelong 2 research vessel.

With three key properties, nickel silver is widely used in shipbuilding, chemical engineering, electronics, and decoration, and holds great potential for lightweight design and green manufacturing.

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