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Comparing Duplex Stainless Steel with Austenitic and Ferritic

by Aug 8, 2019News

ferritic-stainless-steel-pipesAlso known as S31803 or 2205, duplex stainless steel is an anti-corrosive steel combining both austenitic and ferritic properties. As you might expect, it shares quite a few similarities with the austenitic and ferritic classes, both in consistency and function.

Nonetheless, it is different, carrying pros and cons that are all its own. Wondering how exactly duplex compares with austenitic and ferritic stainless steels? This article has some of the information you will need to know.


Austenitic stainless steels are low in carbon, but high in nickel. They possess between 16% and 26% chromium, and between 6% and 22% nickel.

Ferritic stainless steels are high in chromium, but low in everything else. They consist of between 12% and 30% chromium, and of less than 0.1% carbon, with only traces of nickel present.

As was noted above, duplex stainless steel is a combination of ferritic and austenitic stainless steel. It consists of between 17% and 30% chromium, and of between 3% and 13% nickel.

Corrosion Resistance

When it comes to corrosion resistance, all three of our stainless steel classes have something to offer.

Ferritic stainless steels are the least corrosion-resistant of the three, but still offer reasonable resistance against water-based corrosion, chloride-based corrosion, and stress corrosion cracking. Duplex and austenitic stainless steels are exceedingly resistant to corrosion, capable of thriving through the above-reviewed types of corrosion for prolonged periods of time.

In essence, if you’re buying with corrosion-resistance as your main priority, you should seek out either a duplex or austenitic stainless steel. The specific alloy you choose will depend upon your other priorities.


In terms of strength, duplex outperforms both ferritic and austenitic stainless steels. Though austenitic and ferritic steels possess suitable strength, it’s rare that a person would ever use them with strength as his or her major priority.

Duplex, on the other hand, can hold substantial amounts of weight with only a small structural base. This enables manufacturers to use it in thin strips, thus allowing them to keep their products at light weights without sacrificing functionality.


You might be under the impression that all metals are magnetic. You would, unfortunately, be wrong. The truth is that metals vary in magnetism, often based on the amount of iron that they contain.

The most magnetic of our three steel classes is the ferritic class. Along with martensitic steels, ferritic steels provide top-notch magnetism.

Next up on the list is the duplex class. While not as magnetic as the ferritic class, it’s still more than capable of attracting other metals.

Austenitic stainless steel is at the bottom of the magnetism totem pole. It’s not magnetic at all, not even in the slightest.


The function of austenitic, ferritic, and duplex stainless steel varies wildly. This is due, in large part, to the fact that there are so many ferritic and austenitic steel alloys available today.

For instance, while some austenitic stainless steels are used to make silverware, others are used to make processing equipment. While some ferritic stainless steels are used to make vehicle exhaust systems, others are used to make food equipment.

Duplex stainless steel remains fairly firm in its applications, however. It’s used heavily in the chemical processing and oil industries, as its anti-corrosive properties allow it to withstand abrasive chemicals.

Looking for Duplex Stainless Steel Items?

Are you on the search for duplex (S31803 or 2205) stainless steel items? If so, Great Plains Stainless is the company to call.

We supply stainless steel items to countries all over the world. Whether you’re looking for pipes, bars, fittings, or otherwise, we can supply them to you.

Contact us now to discuss your duplex needs!