Stainless steel: Why doesn't it rust?

Why stainless steel doesn't rust?

Steel is a metal alloy made up mainly of iron and carbon. There are several types of steel, some of which are stainless. But why doesn't stainless steel rust? To answer this question, we will present the specificities of this steel to you.

  1. Stainless steel, Stainless steel, 316L steel what are the differences?
  2. Steel an oxidizable alloy
  3. From steel to rust-free stainless steel!
  4. So what are the characteristics of 316 and 316L steel?

  5. Why 316L in our watches?

 

1. Stainless steel, Stainless steel, 316L steel what are the differences?

Steel is a metal alloy consisting mainly of iron but also of carbon. The carbon added between 0.02% and 2% transforms iron into steel and makes it even stronger but also gives it some "flexibility", which is why steel is widely used in construction. At this stage the steel is not a stainless alloy. Beyond 3% carbon, iron becomes cast iron, but this large amount of carbon makes this metal very hard but also brittle. This is why at present iron is hardly used in its raw form but almost automatically converted into steel.

 

2. Steel an oxidizable alloy

Raw steel is an oxidizable alloy. It will naturally bind with oxygen molecules present in air or water through redox reactions. This reaction is more commonly called "corrosion". These reactions result in the appearance of iron oxide and hydroxide, also known as rust, the famous red-orange substance found on certain iron structures. Rust is a destructive agent that consumes steel, and initially leads to the creation of small holes in the surface of a steel element, until the latter completely decomposes. Hence the need to create a durable alloy over time that escapes these reactions.

 

3. From steel to rust-free stainless steel!

Strauss and Maurer, two German chemists filed a patent in 1912 to exploit the first stainless steel, a clever mixture of steel and chromium (the discovery of which dating from 1797 is attributed to the French Nicolas louis Vauquelin) and nickel (discovered in 1751 by Axel Frederik Cronstedt), which makes the steel very resistant to corrosion and prevents it from rusting. The Chromium content of stainless steel is at least 10.5%, its Carbon content must be less than 1.2% and its Nickel content around 8%.

There are 3 categories of stainless steel: ferritics, martensitics and austenitic stainless steels.

 

4. So what are the characteristics of 316 and 316L steel?

316L steel is a type of austenitic stainless steel, the carbon content of which does not exceed 0.02%, the amount of chromium is around 17%, and the content of nickel reaches 10 to 12.5%. To this alloy is added 2 to 2.5% Molybdenum.

The L in the abbreviation 316L signifies that this is a "Low Carbon" steel. As mentioned above, this steel contains only 0.02% carbon against 0.05% for "conventional" 316 steel. When welding at very high temperatures, a substance called "chromium carbide precipitation" is created and therefore the steel, although stainless, becomes more prone to corrosion. Having a minimum of carbon in the structure of this alloy prevents the creation of this precipitation and therefore the steel is not subjected to corrosion.

Molybdenum, discovered in 1778 by Carl Wilhelm Scheele, is added to stainless steel to form 316L steel. On the one hand, Molybdenum hardens the alloy but above all makes it much more resistant to corrosion, even in extreme environments (chlorinated, salty, and acid environments) which allows the steel to not rust. This is why 316 L steel is also used for outdoor uses such as guardrails or handrails.

 

5. Why is 316L in our watches?

For all of our men's watches and our ladies watches we have chosen to work with 316L stainless steel. You will understand this alloy is recognized for its durability and also its high resistance to corrosion, 2 elements that we consider essential for the case of our mechanical watches. From an aesthetic point of view, 316L steel is a stainless steel whose luster lasts over time and does not tarnish.

Finally, 316L steel is very easily and completely recycled. So stainless steel watches can have a new life. Stainless steel can be recycled endlessly without losing its quality. The commitment from an ecological point of view being one of the strong values ​​at Charlie Paris, it is naturally that we turned to this type of steel for ourMade in France watches

 stainless steel automatic watch

fit stainless man



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