Copper recycling and sustainability Back Ford
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Bronze and recycling
Bronze statue
'The Meeting Place' by British artist, Paul Day, is made of bronze and contains 30% recycled material. The statue stands in the new St Pancras International Station.

Historically, bronzes were used for their hardness, strength and easy castability and gave their name to a period of time known as The Bronze Age. However, bronze is not simply an alloy of the past; it is very much used in modern engineering applications.

Ancient bronzes consisted mainly of copper and tin and are called tin bronzes. Tin bronzes are still used today but bronzes containing aluminium, nickel, manganese and silicon have been developed to give increased strength and corrosion resistance. These bronzes are used in seawater applications and are fully tested to meet stringent government requirements.

An example of the use in seawater is the propeller of a container ship (see image). This was sand cast in nickel aluminium bronze and weighed 95 tonnes. It was produced in one continuous pour and was fed with liquid bronze for 24 hours, since during solidification the bronze contracted.

It was made from almost 100% scrap which was sourced from in-house process scrap from other projects, together with carefully controlled bought in scrap.

It is clear that over the centuries bronze has been recycled to good effect, another example of the sustainability of copper alloys.

The use of these bronzes in applications such as pumps, valves, propellers, pipe fittings and chains is wide-spread and an example of this is shown in the dismantling of a Russian nuclear submarine, where 180 tonnes of this alloy was recovered for recycling.

Bronze propeller
95 tonne aluminium bronze propeller for a container ship (courtesy Stone Manganese Marine Ltd)

Architects also use bronze widely to enhance the appearance of their buildings, taking advantage of its attractive colour, corrosion resistance and high strength. A good example of this is Portcullis House, the parliamentary building, which is clad in aluminium bronze plate .

Thousands of years ago bronze was used to produce iconic statues such as the Colossus of Rhodes. This was destroyed by an earthquake in 224 BC and the pieces were sold. The scrap bronze needed 900 camels to carry it away for recycling.

Bronze continues to be used as the first choice for modern statues; recent examples being those of Bobby Moore (outside Wembley Stadium), Nelson Mandela (in Parliament Square) and 'The Meeting Place' (in St Pancras International Station, London).

These bronzes have similar compositions to the ancient bronzes, being alloys of copper, tin, lead and zinc. Discarded old bronze castings can be remelted and this recycled material used to make new statues. Statues typically contain 30% recycled material. No bronze is thrown away; it is always reused just as it was in 224 BC. We can even imagine that some of this ancient bronze is in the statue in St Pancras International Station.

Portcullis House
Portcullis House, Parliamentary Building, with its aluminium bronze roof and cladding.

The Victoria Cross (VC) is the highest military decoration for valour. It was first awarded in 1856 by Queen Victoria. The medal is produced using bronze recycled from two Chinese-made cannon used at Sebastopol during the Crimean War (1854-56). The bronze contained 10% tin.

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