Duplex stainless steels are graded for their corrosion performance, normally determined by their alloy content. Super-Duplex falls under this family of grades. The term was first used in the 1980s and was used to classify Duplex that had a pitting resistance of >40 (based on Cr% + 3.3Mo% + 16N%).

Super Duplex has all the benefits of other duplex steels, specifically the strength benefits of their biphasic structural composition of equal parts austenitic and ferritic stainless steel. This microstructure makes all duplex steels around twice as strong as regular single structure ferritic or austenitic steels, but Super Duplex has a higher chromium and molybdenum content, giving it considerably increased resistance to corrosion than its counterparts.

Super Duplex vs Duplex

Super duplex stainless steel and duplex stainless steels both have the same three metals in common, these metals are present at different levels. Duplex consists of 22% chromium, 5-6% nickel and 3% molybdenum. Super duplex, meanwhile, contains 25% chromium, 7% nickel and 4% molybdenum. The higher levels of these elements is what gives super duplex its enhanced resistance to corrosion against duplex stainless steel.

Super duplex steel, largely due to its higher nickel content, is more expensive than duplex stainless steel. Super duplex, however, can withstand corrosive environments such as those found in marine or petrochemical industries for a longer time than duplex and is higher in strength.

Applications of Super Duplex

Super duplex is particularly suited for the following applications:

  • Heat exchangers, tubes and pipes for processing gas and oil
  • Pipes in processes containing chlorides
  • Cargo tanks – piping for chemical tankers
  • Shafts, rotors and hydraulic lines

The high strength and low corrosion of super duplex means it is widely used in the following industries

  • Petrochemical
  • Water desalinisation
  • Chemical processing
  • Marine and shipping
  • Oil and Gas production

Super Duplex Equivalent Names:

 25Cr Duplex | 2507 | UNS S32750 (F53) | IMS S32760 (F55) | 1.4410 | Alloy 2507 | SAF 2507 | Super Duplex S32760 | Super Duplex S32760 | X2CrNiMoN25.7.4 | Stainless Steel Super Duplex | 2750 | Duplex 2507 | 1.4501 | Zeron 100 |Super Duplex 2507 | Duplex 2507