Copper and Zinc Metallurgy: Properties, Alloys, and Industrial Uses

Copper: Properties and Applications

Copper is reddish in color with a metallic luster. It is characterized as one of the best conductors of electricity and heat. Thanks to its high electrical conductivity, ductility, and malleability, it has become the most widely used material for manufacturing electrical cables and various electrical and electronic components. Copper is a highly durable metal because it can be recycled almost indefinitely without losing its metallic properties.

Refining Copper

Copper refining is the process of removing impurities that make the metal brittle (both cold and hot). This process facilitates rolling and drawing into wire and thread, ensuring optimal application for electrical conductors, as impurities significantly reduce conductivity.

Key Properties of Copper

Physical Properties

• Reddish metallic luster.
• Element with the highest electrical and thermal conductivity.
• Affordable and recyclable indefinitely.
• Resistant to corrosion and oxidation.

Mechanical Properties

• Good machinability (easy to machine).
• Very good ductility and malleability.
• Soft metal.
• Tensile strength is 210 MPa; yield strength is 33.3 MPa.
• Exhibits better properties at low temperatures (T°), allowing use in cryogenic applications.

Chemical Properties

Copper has a lower oxidation state.

Copper Patina Formation

When copper is exposed to atmospheric agents, a thin coating of green or blue-green corrosion forms on its surface. This durable layer, called patina, has a complex structure and composition. It is highly prized for its great aesthetic value and also protects the inner metal from progressive corrosion. The time required for patina formation varies greatly with geographic location. Copper patinas are heterogeneous and porous, allowing them to absorb large quantities of water.

Copper Alloys: Brass and Bronze

From a physical point of view, pure copper has very low yield strength and low hardness. When alloyed with other elements, copper gains significantly higher mechanical properties, although its electrical conductivity decreases.

Brass (Cu-Zn)

Brass is an alloy primarily composed of copper and zinc, often including other metals. The characteristics of brass depend on the proportion of elements involved in the alloy. Brass is harder than copper, yet it is easy to machine, burn, and melt. It is resistant to oxidation and saline conditions, and it is highly malleable. It has a bright yellow color.

• Applications: Weapons, boilers, welding, and the fabrication of wires.

Bronze (Cu-Sn)

Bronze is an alloy of copper and tin. Yellowish bronze castings are generally of better quality than brass, but they are harder and more expensive to machine.

Zinc: Characteristics and Uses

Zinc is a bluish-white metal. Dry air does not attack zinc, but in the presence of moisture, it forms a surface layer of oxide or carbonate that insulates and protects the metal core from corrosion. The metal has a high resistance to plastic deformation, which is reduced when heated.

Forms and Applications of Zinc

At a temperature (T) of 100–150 °C, zinc can be laminated, pressed, and stretched to form bars, plates, and wires (Rolled Zinc).

• Molten Zinc: Has a lower hardness and strength compared to rolled zinc.
• Pressed Zinc Forms: Zinc pressing results in flexible and malleable forms, used for profiles, wires, and pipes.
• Other Applications: Zinc is used for roofing, gutters, cornices, and similar construction elements.

The main application of zinc is galvanizing steel to protect it from corrosion.