The use of superduplex stainless steels has considerably increased in the 90s. The combination of high mechanical properties and an improved corrosion resistance in numerous industrial media explains this phenomenon, as well as their cost effectiveness compared with high nickel superaustenitic stainless steels or nickel base alloys.

Appreciable improvements of the metallurgical knowledge have allowed to obtain a satisfactory structural stability and an increase of the welding properties, mainly due to a good equilibrium of the chemical analyses with high nitrogen levels. Such results have led to increase the reliability of the superduplex materials and to open new markets for their use.

The corrosion resistance of superduplex grades was also extensively studied and their performances in terms of localised corrosion or stress corrosion cracking in chloride containing media, general corrosion in acidic environments, as well as abrasion corrosion resistance are now unanimously recognised. The sulphide stress corrosion cracking resistance of such materials is also very promising for development of these stainless steels in oil and gas industries.

In the first part, the paper presents some laboratory data obtained on unwelded and welded 25% Cr superduplex stainless steels, in different acidic, chloride and/or H₂S containing environments, representative of some industrial applications for the materials.

Then, industrial experiences of the use of UR 52N⁺ are discussed. Some typical applications, in the fields of seawater, hydrometallurgy, pollution control, chemical or oil and gas industries are presented. The use of this type of materials for such environments should know further developments, on the basis of research results and field experience.