Welcome back to our watch material post part 2. Previously, we explored stainless steel as the material for watches. Moreover, we also discovered some stainless steel watches. If you missed out on our previous post, you can click here to read all about it. Today, we will be exploring further about stainless steel, particularly how did it obtain the name stainless. Therefore, if you are ready, let’s head straight to the post.
Watch Material- Stainless Steel (Source: Drmenstyle.com)
WHAT CAUSES CORROSION/ RUST?
Corrosion is a natural phenomenon that occurs in nature. In fact, it is just a general name given to a layer of metal oxides or hydroxides which formed when it comes into contact with moisture and oxygen. In the case of steel rust, it is because of the reaction between the iron atom and the oxygen and moisture in the air.
Iron Oxide (Rust) (Source: Microfinancejournal.com)
In nature, iron is always in combination with other metals. However, iron is combined with carbon during the processing of steel. However, iron is more reactive than carbon and it tends to be very reactive and unstable. As a result, an iron atom reacts with the oxygen and moisture to form iron oxide. The iron oxide layer has a tendency to spread throughout the area where there is no oxide layer. It is this red-brown layer which we called rust.
WHY DOES STAINLESS STEEL NOT CORRODE?
The key player for stainless steel is the addition of chromium. In the case of stainless steel, chromium is the one that reacts with the air and moisture. As a result, it forms a layer of very thin, but strong chromium oxide. It is this chromium oxide layer that helps to prevent rust, maintaining the steel’s shine. Unlike iron oxide, it is very stable and will not spread to all the parts of steel.
Chromium-Oxide Formation (Source: thefabricator.com)
Therefore, we now know the secret of stainless steel and its superior corrosion resistance. In our next series, we will explore different grades of stainless steel. While we have 5 main grades, and 100’s of classes, only certain grades are suitable for watches. Until then, stay tuned.