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Duplex is a stainless steel made from a mixture of austenite and ferrite phases. Like most austenitic stainless steels, duplex has a strong resistance to corrosion, similar to those of a Type 304 and 316.

Unlike similar steels, duplex also displays an improved resistance to localised corrosion, particularly pitting, crevice corrosion and stress corrosion cracking. And because duplex has a lower nickel and molybdenum content than other austenitic stainless steels, it can prove a more cost effective option due to a lower alloying content.

Due to its ferretic qualities, duplex steel also shows very good resistance to stress corrosion cracking when compared to standard austenitics.  In some cases, the strength of duplex steel can be up to double that of the most commonly used grades of stainless steel.

Duplex becomes brittle at extreme temperatures so its use is normally restricted to a maximum temperature of 300 degrees. Duplex also shows signs of embrittlement at –50 degrees.

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