Metal dusting is "a catastrophic form of corrosion that occurs when susceptible materials are exposed to environments with high carbon activities." The

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

manifests itself as a break-up of bulk metal to metal powder. The suspected mechanism is firstly the deposition of a

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

layer on the surface of the metal, usually from

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

(CO) in the vapour phase. This graphite layer is then thought to form

metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...

M₃C species (where M is the metal), which migrate away from the metal surface. However, in some regimes no M₃C species are observed indicating a direct transfer of metal atoms into the graphite layer.On the Mechanism of Metal Dusting Corrosion (no date) C.M. Chun, J.D. Mumford and T.A. Ramanarayana

/ref> The temperatures normally associated with metal dusting are high (300–850 °C). From a general understanding of chemistry, it can be deduced that at lower temperatures, the rate of reaction to form the metastable M₃C species is too low to be significant, and at much higher temperatures the graphite layer is unstable and so CO deposition does not occur (at least to any appreciable degree). Very briefly, there are several proposed methods for prevention or reduction of metal dusting; the most common seem to be aluminide coatings,

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

ing with copper and addition of steam. There is a significant amount of literature in existence that describes proposed mechanisms, prevention methods etc. There is also a good summary of metal dusting and some prevention methods in 'Corrosion by Carbon and Nitrogen - Metal Dusting, Carburisation and Nitridation' Corrosion by Carbon and Nitrogen - Metal Dusting, Carburisation and Nitridation; Grabke, H.J., Schütze, M.; ''Woodhead Publishing'' 2007

References

Corrosion {{corrosion-stub