Why Stainless steel doesn't Corrode Compared to other Steels

Stainless steel is known for its ability to resist corrosion. It is widely used for food and catering, architecture and construction, automobile and transportation, medical, and energy and heavy industries. Before we proceed to an in-depth discussion, let us first look back to the time when stainless steel was discovered.

History

In 1913, while working on a project to improve rifle barrels, an English metallurgist named Harry Bearly accidentally discovered that addition of chromium to low carbon steel gives stain resistance. Aside from iron, chromium, and carbon, he also finds out that modern stainless steel may also contain other metals, such as niobium, titanium, molybdenum, and nickel. This element can improve the stainless steel corrosion resistance.

Difference of stainless steel from other steel

The difference of stainless steel from carbon steel is the amount of chromium content present on it. Chromium is a crucial component of stainless steels. When 12% chromium is added, it significantly improves corrosion resistance. The metal also improves strength, hardenability, wear resistance, and response to heat treatment.

The chromium present in steel reacts with oxygen in the atmosphere forming a thin transparent layer of chrome-containing oxide which is known as passive film. This film layer prevents corrosion of metals by blocking oxygen diffusion to the surface. It also stops the oxidation from spreading into the bulk of the metal. If metal is scratched or cut, and the passive film is damaged, rapid formation of oxide will occur that will recover and protect the exposed surface from oxidation corrosion.

However, Carbon steel that does not contain chromium when exposed to air and moisture corrodes and rust quickly. This active rust or iron oxide film spreads the corrosion creating more iron oxide. Because iron oxide is denser than the steel, the film expands causing it to peel off and fall away.

Therefore, stainless steel doesn’t corrode or rust compared to other metals because of the presence of chromium. With the help of passivation, steel can be a stain ‘less’ material. It is vital that we know the facts about steels because it will help us to choose what material is best to use. It will easy for us to decide whether we should use low carbon steel or stainless steel.

I hope you learned something today.
Keep steeming. Best regards @lymierikxz

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References:
https://en.wikipedia.org/wiki/Stainless_steel
https://www.metalsupermarkets.com/most-common-uses-of-stainless-steel/
http://www.bssa.org.uk/faq.php?id=4
https://www.thebalance.com/common-steel-alloying-agents-properties-and-effects-2340004