Nord-Lock Group Zajímavosti Mythbusters: A common misconception is that stainless steel is never affected by corrosion

Mythbusters: A common misconception is that stainless steel is never affected by corrosion

The Myth: A common misconception is that stainless steel is never affected by corrosion.

The Truth: In fact, all kinds of stainless steel can rust in poor conditions. It is, however, rarely a question of uniform or general corrosion but rather pitting or crevice corrosion, which is a consequence of the passive layer becoming damaged or being prevented from being rebuilt (repassivation).

Steel with a minimum chromium (Cr) content of 10.5% is known as ‘stainless steel’. Stainless steel has the ability to create a protective layer of chromium oxide, also known as a ‘passive layer’. Other alloying elements such as Nickel (Ni), Molybdenum (Mo) or Niobium (Nb) help to increase the corrosion resistance.

Crevice corrosion can be a result of repassivation being prevented due to lack of oxygen, for example, under the bolt head. Pitting corrosion may occur when the passivation layer is damaged locally. The unprotected steel underneath the passivation film then becomes anode and the material that is covered by the passivation layer becomes cathode. The corrosion process then progresses in a similar way to galvanic corrosion. Chloride-rich environments such as seawater, as well as acid environments or high temperatures, will always increase the risk of corrosion problems occurring.

More insights and references

Combating Corrosion and Protection for Fasteners Any metal product will eventually rust. How corrosion happens and why choosing the right materials and corrosion protection for the bolt is crucial? Více informací
Does Adhesive Works as a Lubricant During Tightening? Chemical thread locking is a traditional solution used against bolt loosening, but does it has the same effect as a real lubricant? Více informací
The History of the Bolt When were the first bolts made and what were they used for? Nord-Lock Group traces the history of the bolt, from ancient Egypt through to modern day bolts & screws. Více informací
Thread Standards: The Search for a Red Thread Let's explore the history, the evolution and the future of these crucial but often overlooked thread standards. Více informací
Comparison of Common Bolt Tightening Methods Tightening methods can be categorized according to the principle of how the preload is generated. The 2 basic principles are rotational tightening and tensioning. Více informací
Fastener quality: All in the details Quality fasteners are essential for safe, economic designs. But what determines quality, and how do we make sure we obtain good quality? Více informací

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