Abstract
Samples of two Cr and / or Al-containing Fe-base alloys were exposed to gas mixtures with oxygen and chlorine activities similar to those expected to be established in the heat-recovery-boiler section of a coal gasification plant under development. Alloy samples were prepared by either SiC-paper grinding, diamond-paste polishing, shot-peening or electropolishing. Analyses of the oxidized samples showed that sample mass changes, morphology and composition of the product scales depended on sample surface preparation and the nature of gas mixtures. Physical properties of sample surfaces which affected scale formation and evaporation of metal chlorides from the alloy matrix were proposed as possible reasons for the observed dependency. The results indicated that sample preparations that produce rough surfaces may be effective in reducing the adverse effect of HCl gas on high temperature corrosion of alloys by promoting the development of protective Cr-or Al-rich corrosion product scales.
