Fairly early in the development of ResponsibleSteel I was contacted by a multinational clothing company which was reviewing its sustainability strategy. They were looking at all the materials their products were made from, investigating the social and environmental impacts of those materials, and asking how they could specify materials in their supply chain more sustainably. We had a good discussion about steelmaking and sustainability. And then they asked, “and what about iron?“

It was a fair question. They had been told that their products contained a whole range of materials, including iron and steel. They were both metals. And they wanted to know, for both of them, what were the issues and how could they address them.

It was a good lesson, not to make assumptions about people’s level of knowledge in a subject you happen to be familiar with. So what is the difference between iron and steel?

The simple answer first. Iron is a chemical element, just as oxygen, hydrogen, carbon or gold are chemical elements. When stars blow up in supernovae explosions they create iron atoms through nuclear fusion. The chemical symbol for iron is Fe, from the latin word for iron, ferrum. Iron is a pretty common element in the universe – the commonest of the elements the planet earth is made from (earth’s core is a great molten mass of iron) and the fourth commonest in the earth’s crust. But iron reacts easily with oxygen if there’s any water about (hence, rust), so almost all of the iron in the earth’s crust is now in the form of minerals, rather than in its pure, metallic state.

To extract metallic iron from those minerals requires a lot of energy – you have to make it really hot – and you have to have to heat it in the presence of elements that will react more strongly with oxygen than the iron itself. Historically, that has been carbon, originally from charcoal. But once people worked out how to do that, three or four thousand years ago, there was no stopping. The rest, as they say, is history. The use of iron, not least to make weapons and agricultural implements, gives its name to the ‘iron age’, and 95% of all the metal produced today is still iron.

So perhaps a better question than “and what about iron?” would have been ‘and what about steel?” Because steel is, basically, iron. It is just iron with added ingredients. Those ingredients, and the way they are combined with the iron itself, give iron – or rather steel – almost magical properties. You could think of it as being similar to the relationship between flour and bread. Bread is basically flour and water. For sure you can mix flour with water, cook it, and eat it – although it isn’t particularly exciting. But add a small amount of salt or sugar, yeast or eggs, butter or oils, herbs and spices – knead it, let it rise and then bake it – and you’re in another world, a world of almost infinite breads and cakes and pastries.

And that’s what steel is. Start with iron. Add carbon. Add other metals: chromium and nickel to stop it rusting; tungsten or cobalt to make it harder: manganese or niobium to make it stronger and more durable. Cool it. Reheat it. Cast it, roll it or hammer it. Coat it with tin, or zinc. Now you have magnetic steels, non-magnetic steels, stainless steels, machine steels, tool steels…

So what is the difference between iron and steel? Iron is to steel, as wheat is to bread, cakes and croissants.

Enjoy.