Duplex stainless steels are extremely corrosion resistant, work hardenable alloys. Their microstructures consist of a mixture of austenite and ferrite phases. As a result, duplex stainless steel display properties characteristic of both austenitic and ferritic stainless steel. This combination of properties can mean some compromise when compared with pure austenitic and pure ferritic grades.

Duplex stainless steels are in most cases, tougher than ferritic stainless steel Strengths of duplex stainless steel can in some cases be double that for austenitic stainless steel.

Whilst duplex stainless steels are considered resistant to stress corrosion cracking, they are not as resistant to this form of attack as ferritic stainless steel. However, the corrosion resistance of the least resistant duplex stainless steel is greater than that for the most commonly used grades of stainless steel, i.e. 304 and 316.