The 2101, 2205 and 2507 are duplex stainless steels. They have two phases: austenite and ferrite. The metallurgical characterization was performed by means of Scanning Electron Microscopy (SEM) with EDX and X-ray diffractometry (XRD). The corrosion behaviour was evaluated by potentiodynamic tests. The corrosion tests were conducted with the aid of potentiostat. The SEM and XRD revealed phases of austenite and ferrite without any intermetallic phase. The elemental analysis of the phases showed that the elements partitioned more into the phases that they promoted. The corrosion resistance of 2507 was higher than 2205 and 2101 as it may be seen on the polarization curves. Comparing the two media, the following relation to their corrosion resistance: 2507 > 2205 > 2101 was established.