| Abstract: | Pitting corrosion susceptibility of the heat treatable steel X20Cr13 in sodium chloride solutions For blades in steam trubines it is common to use the heat-treatable steels with 13% Cr (X20Cr13). Cracking of blades in the region of the turbine, where the steam starts to get wet, have often been referred to be caused by corrosion fatigue. The fatigue cracks sometimes start at inclusions in the material, but more often at pits caused by pitting corrosion. Pitting is brought about by chloride containing blade deposits. To examine the pitting behaviour of the steel in NaCl-solutions we measured the mixed-potential, the potentiostatic piting potential, the mass-loss and the pits per area as depending on temperature (20–80°C), pH (5–7–9), oxygen content (20 μg/kg up to saturation with oxygen) and chloride content (8×10?5 mole/l up to saturation with NaCl 5,4 mole/l). The results show that steel X20Cr13 suffers pitting corrosion because of it's low Cr content in all technical possible NaCl solutions down to a Cl content of 10?5 mole/l at the mixed potential. |
