The material for the euro cents was developed in Sweden.
Imagine - the long line of coins from the Roman Empire, the Vikings, the French and the German empires all reappearing today as euro coins! says Mariann Sundberg
Mariann Sundberg, a metallurgist and R & D specialist at Outokumpu Copper in Västerås, Sweden was the person in charge of the development of the copper alloy, Nordic Gold, used in the 10, 20 and 50 euro cent coins which were introduced in January of 2002.
Nordic Gold is an alloy which combines copper (89%), with smaller quantities of aluminium, zinc and tin. It was originally developed more in the 1980’s for the Swedish Mint and is today being used for the Swedish ten-crown coin.
When the Swedish Mint was looking for a new material for the ten-crown coin, they identified a number of performance criteria that had to be met by any material submitted for approval. The Mint specifically wanted the following:
• The appearance of the coin had to be golden and tarnish-resistant. No discolouration of the golden color should occur over time.
• The material had to be malleable (formable) to make the minting process easy.
• The material had to be durable and resistant to long usage and heavy handling.
• And, equally importantly, the Mint was very concerned about possible allergic reactions caused by some metals, so the new material had to be non-allergenic.
The final Nordic Gold alloy was able to meet all of these requirements and has now been used in the Swedish ten-crown coin for over ten years.
Colour – one of the challenges along the way
One of the major challenges was the colour of the metal. Copper is the only metal, besides gold, with a colour that differs from grey. By alloying the red-brown copper, the colour of something like a coin can be changed considerably to obtain a look much closer to gold, hence its name, Nordic Gold. The second key challenge was to ensure the tarnish resistance of the coins. The material was tested for its reaction to, amongst others, hand sweat, leather, and various clothing fabrics. A number of combinations were tested, and as it turned out, the most tarnish-resistant combination was copper alloyed with aluminium, zinc and tin.
Concerns about allergic reactions
The Swedish Mint was concerned because research has shown that other traditional metals used in coins can present certain people with contact allergy reactions. This made the combinations very tricky to ensure that copper was combined with metals that minimised this possibility. Nordic Gold was ideal in that it induced little to no allergic reaction. A parallel health concern to be addressed was that of hygiene. The daily handling of coins can provide an easy way for bacteria to spread quickly from one individual to another. Copper has the unique characteristic of being a naturally antibacterial material. This hygienic aspect of copper is very well known and explains many of copper’s other uses, such as doorknobs and handles in antiseptic environments like hospitals.
Security features of the coins
The security features are perhaps the most complex, because this new currency was being introduced simultaneously across such a wide area. Obviously, when the original work with the Swedish Mint was done lot of these concerns were already addressed.
For example, vending machines across Europe must have a way of identifying coins, including those minted and issued by other countries, as real. This requires every coin denomination to have a unique “electronic signature”.
In addition, the electrical conductivity of the coins is important to identify coins. Again, this is where copper is a great choice. It’s excellent electrical conductivity can be changed over a large range of values by different alloy additions. Nordic Gold possesses just the right level of conductivity to meet security standards.
Malleable and durable at the same time
Copper’s malleability enables the mint to use a much more efficient process in stamping the coins. The Copper alloys are cast into cakes or thick strips and then rolled to the correct coin thickness. The coin blanks are stamped from the finished strip and then rimmed and minted. One of the best things about copper is that it is malleable enough to allow fairly complex reliefs, as you will see on the euro coins. During embossing, the coins are further hardened, with copper’s resistance to corrosion then ensuring a long life.
Copper’s recyclability
Copper is fully recyclable, which in this time of increasing environmental consciousness, made it even more of a perfect choice for the currency. It is well known that the remelting and reuse of copper has been practised since the Bronze Age. It is estimated that more than 80% of all the copper ever mined is still in use today and the value of scrap material, at the end of its useful life, will guarantee copper’s future recycling.
