Correlation of Oxidation, Carburization and Metal Dusting; “Controlling Corrosion by Corrosion”

Abstract Metal dusting has been observed in industrial high temperature process components such as waste heat boilers in reformers and gas pre-heaters in direct reduction plants. This corrosion phenomenon is a disintegration of metallic materials into carbon (graphite) and metal dust. The degradation takes place in strongly carburizing atmospheres with carbon activities greater 1 (ac≫1) and at intermediate temperatures between 400 °C - 900 °C. Slight modifications in the process conditions may affect significantly the occurrence and extent of metal dusting attack. To correlate high temperature corrosion mechanisms, e. g. oxidation, carburization and metal dusting for alloy design purposes, results of laboratory investigations are compared with field observations and experience. Most of the work described herein is concerned with gas mixtures of hydrogen and carbon monoxide used in the direct reduction of iron ores (DRI). Considerations are given concerning the process variables as well as on the recent development of new high performance alloys which should form an inherent stable oxide layer formation. A controlled formation of a dense, protective, self-healing alloy surface oxide gives reasonable protection of plant components under most aggressive metal dusting parameters.