The science behind the non-rust stainless steel castings

Stainless steel has been a household name for years now. So many things make use of stainless steel, from daily usage items such as spoons and knives to more important things like parts of a machine.

What is it?
Stainless steel as you all must already know, is actually an alloy. Manufactured in a stainless steel foundry it is an alloy of iron containing parts of manganese, chromium, silicon and carbon. Sometimes stainless steel is manufactured by adding nickel and molybdenum to it. Stainless steel since its inception had become an indispensable item both in the factories and in regular use owing to the fact that unlike iron or other metals, it seems to be immune to the degrading effects of oxygen and the atmosphere. Iron when used for long, is likely to rust and start crumbling. Stainless steel, however, is capable of withstanding these natural elements and can be used for years without any signs of tarnish or rust on it.

This property of stainless steel along with the fact that it looks good, and is light weight has contributed to its usage in so many things.
Why does it not rust?

This has been a matter of extensive research ever since stainless steel has been manufactured in stainless steel foundry as an alloy and its special property discovered. Other alloys of iron, are susceptible to the same dangers as iron is, so let us see what makes stainless steel so resistant.

1. The special alloy stainless steel, remains stainless because of the chemical reaction that happens as its components and the atmosphere come in contact. The components of this alloy such as chromium when they react with the oxygen that it might get from water or the air, lead to the formation of a protective layer, something like a very thing coating. This film that is formed is a pretty stable layer and it contains products like oxides and hydroxides of metals. The main element that plays the protector is chromium. All stainless steel contains at least 10% chromium, which helps form the film.

2. Once this film is formed, it prevents the water or air from causing any harm to the underlying alloy. The first attack of atmospheric elements is enough to form the layer and it stays tight and fine on the surface negating the rusting effects. However, we can't actually see this film, because it is absolutely thin, thinner than the wavelength of light. Scientists can see this film once they all their modern gadgets.

3. So technically the steel is getting corroded at its atomic level but we can't see it, and thus the stainless steel products remain stainless. It is very different from normal steel where the layer of corrosion formed is thickened with time and you see a whitish deposit over your steel item. That is the rust, which is very much viable to the naked eye.

There are other metals too which do not rust because of the same reason, like aluminium or titanium. They too form a film that prevents corrosion. Stainless steel, on the other hand, is way cheaper and it has an aesthetic appeal. So you get rust free, aesthetic and durable all in one when you use stainless steel products