Metal dusting: what determines aggressivity?

The degradation mechanism metal dusting occurs in low and high pressure syngas environments between 500 and 700 C. Metal dusting is a combination of both oxidation and carburization effects, in which a (ferritic or austenitic) alloy matrix is supersaturated with interstitial carbon, usually originating from gaseous carbon monoxide. At sufficiently high temperatures, the alloy matrix will decompose into graphite, metal, metal oxide and metal carbide particles, leading to loss of containment. A previous joint industry project (JIP) established a general ranking of the resistance of materials. As yet, it is not known -but vitally important- which material can be used in a certain given gas atmosphere. The ongoing research programme aims to predict the aggressivity of any given syngas atmosphere, thus coupling it to a range of appropriate construction alloys or coatings. ©2007 by NACE International