Metal dusting corrosion initiation in conversion of natural gas to synthesis gas

Ni-based industrial alloy samples (INCONEL® 601) were subjected to oxidizing conditions, followed by exposure to a high carbon activity gaseous mixture containing 10% CO in Ar at 550°C in order to reveal factors critical to the initial carbon-formation. Fresh and treated samples were studied via optical-microscopy, SEM, Auger depth-profile analysis, TEM and EPMA. The results show that the extent of carbon formation is dependent on the oxidation parameters, since these affect both the composition and the structure of the 20-60 nm thick oxide layer formed. A high oxygen partial pressure during oxidation appears to promote inclusion of Ni or Fe species in the oxide, which subsequently reduce and catalyse the growth of carbon filaments. Surface pre-treatment (i.e. polishing before oxidation) is also found to affect the carbon formation.