Super and hyper duplex stainless steels (DSSs) are well-known materials in chemical industry. DSSs are characterized by excellent chloride stress corrosion resistance, very high mechanical strength, excellent resistance to pitting and crevice corrosion. The duplex structure also gives design advantages compared to austenitic stainless steels since the thermal expansion matches carbon steels.

However, DSSs are often optimized for chloride resistance, and therefore the performance in acid environments can be a limitation.

The recently developed UNS S83071 has been optimized for general corrosion resistance, which gives benefits where traditional super duplex grades suffer from high corrosion rates due to general corrosion. The composition is 30Cr-7Ni-3.5Mo-N, and the material is characterized by excellent acid corrosion resistance with the traditional benefits of DSSs, in combination with good structure stability and weldability.

This paper presents the results from general corrosion testing in acid environments and the results from standardized corrosion testing methods. The results show that UNS S83071 has excellent general corrosion resistance as well as excellent resistance to pitting and crevice corrosion, making it suitable to be used in demanding environments, such as acid production plants with or without seawater cooling.


Austenitic-ferritic stainless steels, commonly known as duplex stainless steels (DSSs), are a group of materials typically consisting of equal amounts austenite and ferrite. DSSs are well-known materials in chemical industry and are often a cost-effective alternative as they combine high mechanical strength and fatigue resistance with good corrosion properties. Contributing to the cost-effectiveness is the low nickel content compared to austenitic stainless steels. Advantages with DSSs are high chloride stress corrosion cracking resistance (SCC), where austenitic steels with moderate nickel content are inherently more sensitive. In combinations with carbon steel it can be a benefit to use DSSs since carbon steel and DSSs have matching thermal expansion.

Among the applications where DDSs are selected are where common austenitic stainless steels face problems with chloride pitting or chloride stress corrosion cracking.

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