January 2017

Self passivation of stainless steel: a unique material that can protect itself

Stainless steel is an extraordinary material. It is resistant, ecological, attractive, and a "friend" of potable water. Among all of its winning features, one of the most special is definitely its ability to spontaneously "reshape" its own surface protection layer. We are talking about "self passivation".
Stainless steel is a material with unique characteristics. It has been on the market for over 100 years and nothing but good can be said about it. Resistance, hygiene, and a "unique" feature - its "self-protecting" surface layer and its ability, in most cases, to recreate itself.

We are talking about a phenomenon called "self passivation", stainless steel's ability to recreate independently, on its own surface, a protective layer that shields it a good deal from corrosive processes.

Examples of use of stainless steel in architecture

Example of uses of stainless steel in architecture

There is more than one type of stainless steel. Many variants are available and each has different elements and percentages. Most steels are made of iron alloys, chrome, and other elements that vary such as nickel or carbon. Other metals can also be added depending on the characteristics to be obtained.

The primary player in stainless steel self passivation is chrome. In all environments with an adequate presence of oxygen, chrome reacts with it forming a layer of chromium oxide or hydroxide. This thin layer (with a thickness of just a few atoms, 3 - 5 × 10-7 mm) protects the underlying metal from external agents and further oxygen/chrome oxidation.

Self passivation is a "dynamic" phenomenon. If the film is removed or damaged, under the right conditions the oxide layer is reformed "automatically".

Self Passivation of steel - scheme

The self passivation phenomenon is generally always able to rebuild the protective oxide layer. The only exception is in particularly "severe" circumstances such as when the stainless steel surface comes in contact with blunt objects containing contaminating materials. This article explains contamination with ferrous material.

press-fitting range in stainless steel AISI 316L

When creating quality plumbing systems, one of the best options is definitely 316L stainless steel pressfitting systems. It is a responsible choice because stainless steel is 100% recyclable, has a long life and is reliable over time due to the resistance of the pressfittings along with its extraordinary ability to independently reform its own protective layer.

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