Various austenitic and ferritic steels were exposed on a water-cooled probe in the superheater area of a straw-fired CHP plant. The temperature of the probe ranged from 450-600°C and the period of exposure was 1400 hours. The rate of corrosion was assessed based on unattacked metal remaining. The corrosion products and course of corrosion for the various steel types were investigated using light optical and scanning electron microscopy. The ferritic steels suffered from corrosion mainly via material loss. The austenitic steels suffered from predominantly selective corrosion which resulted in depletion of chromium from the alloy. A clear trend was observed that selective corrosion increased with respect to the chromium content of the alloy.
Materials and Corrosion, 1999, Vol 50, Issue 10, p. 579-584