Duplex Stainless Steels: The Versatile Alloys Available to Purchase

Duplex stainless steels were first manufactured early in the 20th century, but it was the invention of argon oxygen decarburization melting and the addition of nitrogen that made the alloys stronger, more weldable, and more corrosion resistant. Today, there is a family of duplex stainless steels covering a range of compositions and properties, but they all share high strength and good corrosion resistance, especially to stress corrosion cracking, compared with similar austenitic stainless steels. This paper briefly reviews the range of modern duplex stainless steels and why they are widely used in many industries. They are the workhorse corrosion-resistant alloy in the oil and gas industry. In this paper, their use in three industries common in Australia and New Zealand is reviewed: oil and gas, mineral processing, and desalination. The corrosion resistance in the relevant fluids is reviewed and some case histories highlight both successes and potential problems with duplex alloys in these industries.