Duplex stainless steels have gained a large commercial interest in the latest decades due to their good combination of strength and corrosion resistance. Being a relatively new type of material to most users, this family of steels has been subjected to a large variety of tests and specifications.

The paper reviews and discusses some international standards and special requirements regarding manufacturing process, composition, microstructure, corrosion tests and mechanical requirements. Available international standards are generally sufficient to specify for most applications.

The use of quantitative metallography in acceptance criteria is a source of confusion and alternative methods are possible. It is recommended that acceptance of a certain product or procedure should be based on testing of engineering properties of practical concern.

One advantage of using duplex steels in loaded constructions is the possibility to reduce the wall thickness compared to austenitic stainless steels. It is well known that European design rules allow thinner sections and thus better cost benefits than ASME codes. Different regulations and their consequences for duplex steels are discussed.