[ Corrosion in Stainless Steel ]

The air that we breath contains about 21% of oxygen, 78% of nitrogen and the remaining is a mixture of water vapor and carbon dioxide. Every metal reacts with oxygen and water from the air creating a superficial layer of oxides. This layer is porous and allows posterior oxygen and water penetrations. In this way, the oxidation keeps growing and produces the corrosion, which is known commonly as rust. The only way to prevent this corrosion process in the steel is to protect its surface. That can be made with paintings, oils, or non porous pellicle.

The chromium in the stainless steels reacts with oxygen from the air and creates a fine superficial layer. Despite of very thin, this chromium oxide layer is not porous and, therefore, it prevents the steel surface from entering in contact with the atmosphere. This also prevents the steel corrosion caused by the environment.

This adherent and resistant layer is invisible and it allows that the metal natural shine can be seen. It is denominated "Passive layer" and if damaged, it is capable to auto-regenerate almost instantly, keeping the steel protection.