Corrosion Resistance: The composition of duplex stainless steels sets it apart from regular austenitic and ferritic grades in terms of corrosion resistance to aqueous chloride solutions. The pitting resistance equivalent number (PREn) is a calculated value that utilizes specific elements in a grade’s chemistry to roughly rank grades with respect to their pitting corrosion resistance when exposed to aqueous chloride-containing solutions. Duplex stainless steels are often lean in more expensive alloying elements such as nickel, which are substituted with alloying elements such as nitrogen, molybdenum, chromium, and tungsten, which greatly enhances the PREn. The formula for PREn is %Cr + 3.3 x %Mo + 16 x %N. For more in-depth information on the PREn, see our blog, Things to Know About PREn. Additionally, duplex stainless steels are less prone to chloride stress corrosion cracking (CSCC) than austenitic stainless steels like 304/304L and 316/316L due to their dual-phase microstructure. For information on stress corrosion cracking, see our blog, Stress Corrosion Cracking.

Ease of Fabrication: Due to their higher ductility, duplex stainless steels are often more formable than ferritic grades. The higher ductility of duplex stainless steels is attributed to them containing approximately 50% austenite. Duplex stainless steels are also highly weldable in thick and thin sections. To better understand the best practices when welding duplex stainless steel, see our webinar, Best Practices When Using Duplex Stainless Steel.