Metallurgical and environmental factors affecting the pitting behavior of SAF 2205 duplex stainless steel in chloride solutions

Metallurgical and environmental factors affecting the pitting behavior of SAF 2205 duplex stainless steel in chloride solutions

Hosni M Ezuber

College of Engineering, University of Bahrain,

 B. O. Box 32038,

Kingdom of  Bahrain

Fax: +973 17 680935

Email; hzubeir@eng.uob.bh Abstract

The breakdown potential of mill-annealed SAF 2205 DSS has been evaluated in 1 M NaCl solution with and without dissolved CO₂ at temperatures up to 80^oC and flow (agitation) up to 1000 RPM using potentiodynamic polarization technique.
The results were compared with heat treated samples (furnace heated at 850 for 10 or 60 minutes followed water quench). The aim of the heat treatment is to simulate sigma phase precipitation. The results show dependence of pitting potential on the various factors (sigma phase, test temperature, presence of dissolved CO₂, or solution flow) being studied. In general, the mill annealed or heat treated 2205 DSSs are immune to pitting at room temperature (23^oC). At 50^oC however, pitting corrosion is evident and the intensity of such attack is higher for the heat treated specimens and is increased with increasing heat treatment duration, presence of dissolved CO₂, and/or seawater temperature. In contrast, agitation speed of 350 RPM or above (sufficiently to yield turbulent flow) has shifted the pitting potential to more positive values. Lower speed of 100 RPM, however, is negligibly different from the stagnant conditions.