Copper for life. Alloys and coins.

page 4

Alloys and coins

Photo of ancient coins

Picture 7. Ancient Chinese coins. These have survived for thousands of years.

	Alloys

		Sometimes it is better to make an alloy of copper to change or improve its properties. For example, an alloy might be stronger, have better corrosion resistance or a brighter colour. Brass, which is made by melting copper and zinc together, is harder, stronger, more corrosion resistant and has an attractive gold colour. It still keeps its anti-bacterial properties, which makes it a great material for door knobs, handrails and plumbing fittings.

	Healthy coins

		Copper has been used to make coins for centuries. These stay around for years and it is impossible to guess how many times they have been passed from hand to hand.

Photo of copper bracelet

Picture 8. A copper bracelet for arthritis.

		Normally we don't wash our hands before and after handling money. Yet this is potentially a good route for infections to spread. Copper, with its anti-bacterial properties, helps to stop this from happening. Bacteria do not survive on copper coins and since it is a non-allergenic material, people don't get a rash from handling them. Some people actually wear copper to improve their health. Many arthritis sufferers wear copper bracelets so that absorption through the skin can make them feel better.

Photo of euro coins

Picture 8. The modern Euro coins. These have a long life - until they are recycled!

	Coins and alloys

		Mixing copper with other metals produces alloys of different colours. 184,000 tonnes of copper were used for the first production of the eight new Euro coins. the €1 coin has a golden coloured outer ring made of an alloy called nickel brass. This is 75% copper, 20% zinc and 5% nickel. The centre is silver coloured made from nickel coated with an alloy of 75% copper and 25% nickel. the €2 is similar with the alloys reversed; the 10, 20 and 50 cent coins contain 89% copper and the 1, 2 and 5 cents are copper-coated steel.
		(See properties)

	Electrical conductivity

		Vending machines that sell drinks, crisps, chocolate etc. always check that the correct coins have been put in. One of their tests is to measure the electrical resistance of the coins. The composition of the new Euro coins was selected to give them exactly the right electrical resistance.

	Longer lasting

		Copper’s corrosion resistance properties mean that these coins don't tarnish easily - i.e. they stay nice and shiny for a long time. The Euro coins are expected to last for 30 years. Copper can be recycled when the coins reach the end of their useful life. The coins can be melted down to make new copper alloys. Or it is possible to refine them using electrolysis to make very high purity copper (99.9% pure). They can then be used for the highest quality applications. (see recycling)