The main purpose of this paper is to review existing knowledge on meta
l alloy behaviour in contact with highly reducing syngas in coal gasif
ication plants, presently close to commercialization. A secondary purp
ose is to compare laboratory and plant corrosion data. Present commerc
ial practice indicates that most metal alloys will be used as heat exc
hangers to evaporate steam at 350-450 degrees C. Smaller but significa
nt future applications may be superheaters or hot-gas clean-up equipme
nt exposed at 500-600 degrees C. The alloys will probably be in contac
t with non-equilibrium gases quenched from much higher gasification te
mperatures in the range 1000-1500 degrees C. Under these conditions th
e formation of chromiarich protective oxide scares is rarely observed.
The growth rate of less protective oxide/sulfide scales varies consid
erably with temperature, gas composition and alloy composition. For mo
st applications, available Fe-Cr-Ni alloys can be found to provide ade
quate service life, provided carburization after long exposures can be
avoided.