In the last lesson we found that stainless steel is more resistant to external agents thanks to Chrome. This is because the latter is an element capable of passivating and protecting steel from corrosion. But what are corrosion and passivation?
It is the main enemy of all metals. Common steels react with the environment by forming a surface containing iron oxide. This surface is very porous and allows the oxidation process to continue penetrating the steel by corroding the surface and producing what is usually called rust.
Passivation is the property of certain metal elements or alloys (such as stainless steel) to oxidize on the surface. This oxidation creates a very thin homogeneous film that makes the action of the external agents almost nothing and protects the base metal from corrosion. The stainless steel passivation is something that happens naturally at the same time as the alloy is in an environment that can bring oxygen to the surface of the metal. When steel is in contact with an oxygen-rich environment, in fact, chromium tends to form very stable oxides and hydroxides.
Can the passive layer formation be encouraged?
The formation of the passive layer can also be promoted through the use of oxidizing agents. The passive layers formed by the use of baths with a content of nitric acid at 15%-20%, for example, are the most homogeneous and it have oxides-hydroxides richer than chromium.
What are the passivation process advantages?
This process is very important because it restores the stainless properties of the object.
Passivation has several advantages:
- better corrosion resistence
- uniform and smooth finish/appearance
- shiny surface
- easier to clean
- more life of the product.
See you on next Expert Lesson.
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