Properties and Uses of Common Industrial Metals

Metals: Properties, Processing, and Applications

Copper

Classification: Density > 5. Danger 5-2, Ultralight < 2.

Advantages: Electrical and thermal conductivity, oxidation and corrosion resistance, low melting point.

Disadvantages: Lower mechanical resistance, more difficult and expensive to obtain.

Sources:

• Native copper: (Poor mineral, not usually found)
• Sulfides: Chalcopyrite and chalcocite
• Oxides: Malachite and cuprite

Characteristics: Reddish, relatively soft, high electrical conductivity, very ductile and malleable, moderate resistance to acids.

Obtaining Process:

• Wet process: Copper < 10%. Diluted sulfuric acid is added to an electrolytic bath.
• Dry process: Copper > 10%. Crushing, grinding, mineral separation, and gangue by flotation in water, partial oxidation to transform copper sulfide into copper oxide, adding a flux (silica + limestone), copper reduction (reverberatory furnace) to remove sulfur and oxides, electrolytic bath to obtain 99.5% pure copper.

Applications: Manufacturing of electrical cables, pipes, boilers, and heat exchangers.

Alloys:

• Bronze:
  • Ordinary: Copper + Tin (bells)
  • Special: Copper + Tin + other elements (sculptures, cables)
• Brass:
  • Regular: Copper + Zinc (machine parts, screws)
  • Special: Copper + Zinc + other elements (taps, nuts, screws)
• Cuproaluminum: Copper + Aluminum, resistant to corrosion (propellers, turbines, chemical applications)
• Alpaca: Copper + Zinc + Nickel (cheap jewelry and cutlery)
• Cupronickel: Copper + Nickel (hulls)

Tin

Source: Cassiterite (tin oxide), concentration > 0.02%.

Characteristics: Shiny white, slightly ductile, attacked by acids and alkalis, makes a characteristic "tin cry" sound, not malleable at ambient temperature, oxidizes very slowly, soft, fragile, and brittle when hot, becomes powder at -18°C.

Obtaining Process: Cassiterite is ground, screened, placed in a vat with water (separation by flotation, mineral sinks), partially oxidized in a furnace to transform sulfides into oxides, reduced in a reverberatory furnace (tin oxide to tin), and refined in an electrolytic bath to 99.9% purity.

Applications: Tinplate (steel with a layer of tin to prevent oxidation).

Alloys:

• Bronze
• Solder (Lead + Tin)
• Type metal (Tin + Lead + Zinc)
• Low melting point alloys

Lead

Source: Galena (lead sulfide).

Characteristics: Greyish-white, very soft, malleable, high density, low conductivity, easily oxidized (single exterior layer), resistant to corrosion (except nitric acid), attacked by organic acids, absorbs vibrations.

Obtaining Process: Galena is crushed and milled, separated by flotation, roasted at 700°C with silica and lime (sulfide to oxide), reduced with coal and quicklime to obtain lead, and other metals are removed by electrolysis.

Applications: Soldering, toys, paintings, radiation protection in nuclear facilities, batteries, and glass.

Zinc

Sources: Blende and calamine (zinc sulfide and carbonate).

Characteristics: Bluish-gray, shiny, soft, resistant to corrosion and oxidation, not resistant to acids and salts, very high coefficient of thermal expansion, brittle when cold, very malleable at 100-150°C.

Obtaining Process:

• Dry process: Roasting of blende, grinding and calcination of calamine to obtain zinc oxide, reduction of zinc oxide with carbon to produce zinc (98% purity), oxygen, and slag.
• Wet process: Trituration of both minerals with sulfuric acid and zinc powder to obtain dissolved zinc sulfate and impurities, electrolysis to obtain 99% pure zinc.

Applications:

• Alloys:
  • Brass (Copper + Zinc)
  • Alpaca (Copper + Nickel + Zinc)
  • Zamak (Aluminum + Copper + Zinc) for high-precision and high-quality surface parts
• Pure: Sheets of different thicknesses for gutters and cornices.
• Coating of parts:
  • Electro-galvanized: Electrolysis coats a metal with a thin layer of zinc.
  • Hot-dip galvanized: The piece is immersed in a molten zinc bath.
  • Metallic-sprayed: The surface is coated with tiny particles of zinc mixed with paint.
  • Sherardizing: The part is coated with zinc powder and placed in an oven, allowing the zinc to penetrate the piece.
• Other forms: Zinc oxide in sunscreens, deodorants, dyes, glues, etc.