Copper

Copper is a orange/reddish coloured metal which is malleable and ductile. It has excellent thermal and electrical conductivities and good corrosion resistance.

Pure copper has an electrical conductivity second only to that of silver. Hence its main application is in the electrical industry. Copper is also the basis of many important alloys:

  • brass
  • bronze
  • aluminium bronze.

Traditionally considered to be one of the coinage metals, along with silver and gold, but being more common, is the least valued.

  • C101 – High conductivity – used in the electrical/electronic component industries.
  • C106 – available in sheet & strip in coil and tube it has excellent welding properties. It also can be offered in highly polished finishes for architectural purposes.

Abundance

50 ppm in the Earth’s crust.

Annealing

Heat until it glows dull red, then cool (either slowly or by plunging it in water), the copper becomes very soft and easy to bend and work. Note that it will work harden again and you will need to repeat the heating and quenching process.

boiler endplates

Forming boiler endplates from copper plate can be quite easy. I used a former and annealed the copper before pressing the shape in a vice.

Beryllium Copper

Heat treatable copper-beryllium alloy has high strength and hardness. Used for making springs and non-sparking tools.

Brass

A shiny yellow to yellow-orange alloy of 70% copper and 30% zinc, but often other elements such as aluminium, iron, manganese, tin and lead are added.

Bronze

A yellow to yellow-brown alloy that contains mostly copper and tin. However, the name is now applied to other alloys that do not contain tin.

Copper Plating

The process in which a layer of copper is deposited on the item to be plated by using an electric current. I have seen this used to produce exhaust manifolds for a model engine.

Chinese Silver

An alloy used for jewellery, 58% copper, 17.5% zinc, 11.5% nickel, 11% cobalt, and 2% silver.

Discovery

Copper is one of the first metals ever to have been worked by man and is thought to have been mined for more than 5000 years. 1500BC copper is smelted in China.

It is found in sulphide ores and as carbonate, arsenide and chloride. Extraction of the metal involves roasting the ore to produce the oxide, followed by reduction and purification by electrolysis. The element is inert to non-oxidising acids but reacts with oxidising agents. In air, it will weather to produce the characteristic green patina of the carbonate. Copper will combine with oxygen on heating to produce CuO at red heat, and Cu2O at elevated temperatures.

Machining

Not the easiest material to turn. Best turned fast with cutting oil and very sharp tools and it will be fine. The problem with copper is it is malleable and so flows very easily. This means cutting tools need to be sharp to avoid smearing the copper onto the part being machined.

Nickel Brass

A copper alloy containing zinc and a small quantity of nickel.

Patina

A thin layer of corrosion products with a distinctive colouration that forms on a metal surface exposed to air and water. Patina usually refers to the greenish coating that forms on copper alloys over time. In most non-polluted environments it is basic copper carbonate but in industrial and urban areas it is mainly basic copper sulphate. You can treat the surface of metal with heat, paint, beeswax or oil quenching to provide a virtual rainbow of effects and colours.

copper flower

A garden flower made from some old copper sheet. Over time this will develop a patina.

Symbol

Cu

Tumbaga

An alloy composed mostly of gold and copper that has a significantly lower melting point than gold or copper alone.

Verdigris

Verdigris is a mixture of acetates of copper used in making some green pigments. It forms on the surface of copper and brass when they are exposed to damp, and is highly poisonous. The Statue of Liberty was made from copper sheet and has formed a verdigris.

References

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