Stainless steel was discovered by accident in 1913 by the British metallurgist Harry Brearly. He was experimenting with steel alloys – combinations of metals – that would be suitable for making gun barrels. A few months later he noticed that while most of his rejected specimens had rusted, one containing 14 per cent chromium had not. The discovery led to the development of stainless steel.
Ordinary steel rusts because it reacts easily with oxygen in the air to produce crumbly red iron oxides. Other metals, such as aluminium, nickel and chromium, also react in much the same way, but their oxides form an impermeable surface layer, stopping oxygen reacting with the metal underneath. With Brearley’s steel, the chromium formed such a film, protecting the metal from further attack.
A variety of stainless steels are now made. One of the commonest alloys contains 18 per cent chromium and 8 per cent nickel known as 18:8 – which is used for kitchen sinks. Kitchen knives are made of a steel containing about 13 per cent chromium. A more corrosion-resistant alloy is achieved by adding a small amount of the metal molybdenum – these steels are used as cladding for buildings.
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