We have performed a long term comparative study between five wrought and three centricast
materials, both as-is, and in coated condition. Two commercially available coatings were
applied to each different alloy. One coating was aluminum based with a chromium rich
intermediate layer. The other coating was nickel rich with substantial amounts of silicon and
aluminum. Both types of coating were of good quality, and did not show (micro)defects. The
coated and bare alloy samples were exposed in a high pressure metal dusting atmosphere,
and characterised based on mass loss, pit depth, pit size and pit density at regular intervals.
The results indicate that a properly applied coating can boost the metal dusting resistance of
low chromium alloys to a level comparable with alloy 693, for which generally no metal dusting
attack is observed. Finally, the effect of micro cracks on the coating performance was
assessed.
Keywords: metal dusting, syngas, austenitic and ferritic materials, slurry coatings, diffusion
coatings, aggressivity of gases