Why is Stainless Incredible

What is it? What are its benefits? Which grade to choose?

Why Is Stainless Steel Incredible?

Stainless Steel is one of the most used materials around us today and its use can be found in kitchen utensils, automotive parts, marine fasteners and just about every other aspect of life. This short article will look at the basics of stainless steel including its defining structure, advantages of over other materials, as well as some interesting facts like how Stainless Steel is 100% recyclable and sustainable.

So, what exactly is stainless steel? Stainless steel is the name given to a steel alloy that contains a minimum of 10.5 per cent chromium. The chromium is essentially what makes stainless steel work, since the primary element, iron, naturally wants to oxidize and corrode. The chromium content prevents this by combining with oxygen to form an invisible layer of ‘chromium oxide’ on the surface of the metal which prevents the iron from forming rust.

The video below explains stainless steel self-passivation, a process where stainless steel forms a protective oxide layer to prevent corrosion and enhance durability. It covers how this self-repair mechanism works and its benefits in various applications.

Stainless Steel is Incredible! Why?

Because it has a naturally occurring protective layer on its surface that protects it from corrosion. This is due to the chromium it contains – any steel alloy that contains a minimum of 10.5% chromium is considered to be stainless steel.
Stainless Steel Gears

Why is Stainless Corrosion Resistant?

Stainless steel is a solid metal and not just a coating applied to steel. The chromium in the stainless steel combines with oxygen in the normal environment to form a ‘chromium oxide’ or a ‘passive film’ layer on the surface. This protects the iron in the steel from being attacked by corrosive agents (e.g. salt) and creating rust.

When the chromium oxide layer is damaged mechanically or chemically... ...it repairs itself – assuming oxygen (even in very small amounts) is present.

NB: that’s why most stainless steels (except super duplex 2507) don’t perform when submersed in salt water because there isn’t enough oxygen to generate the chromium oxide layer.

Qualities of Stainless Steel

	Rust/Stain Resistant - If the chromium oxide layer is maintained and not under regular mechanical vibration, it should probably last forever.
	Maintains looks over time - Depending on a range of factors (finish, grade, environment, cleaning) stainless should maintain its appearance over time.
	Delivers value for money - In general, it outlasts steel coatings (e.g. zinc or galvanizing), so overall delivers a lower cost over the entire life-cycle.
	Relatively strong - In terms of tensile strength, it can range from 500 to 1000 MPa.
	Recyclable - Stainless steel is 100% recyclable and non-toxic.

Stainless steel is also known as ‘inox steel’ or ‘inox’ from French ‘inoxydable’

How is the Performance of Stainless Steel Improved?

Improved Performance of Stainless Steel

NB: This is provided as a guide only. Anzor does not accept liability for the application of this informaiton. For advice about stainless steel, contact the Nickel Institute.

Types of Stainless Steel

There are more than 60 grades of stainless steel. However, all stainless steels can be divided into one of five types identified by their main crystal structures:

	Austenitic The most commonly used stainless steels (e.g. 304 and 316) accounting for more than 70% of stainless fastener production. It has excellent corrosion resistance, weldability and formability.
	Ferritic These are plain chromium stainless steels (e.g. 430) with very little or no nickel and therefore have a lower cost. However, they have low corrosion resistance and are not often used to make stainless steel fasteners.
	Duplex Duplex stainless steel (e.g. 2507) has a special structure which gives it high strength and resistance to stress corrosion cracking. Its high chromium and molybdenum content also gives it greater corrosion resistance.
	Martensitic Used in the first stainless steels commercially developed (such as cutlery), and have relatively high carbon content. They have moderate corrosion resistance with the benefit that they can be hardened by heat treatment. Examples include 410 and 420.
	Precipitation Hardening (PH) Supplied in a solution treated condition (in which they are machinable). They are hardened after fabrication to achieve very high strength. A common grade is 17-4PH.

Stainless steels are a champion of recycling, with around 95% of end-of-life stainless steels being collected and recycled into new stainless steels without loss of quality. Durability and recyclability are two of the key contributions which stainless steels makes to sustainability. Watch the video below.

There are many different grades of Stainless Steel classed by their main crystal structures. Of course, stainless steel is extremely prevalent in the building, manufacturing and marine industries where many common fasteners, fittings and hardware are used every day.

If you're after any kind of stainless fastener, click here to contact us or call 0800 4 ANZOR to enquire.