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 engine ...

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 Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

layer on the surface of the metal, usually from

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

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

metastable In chemistry and physics, metastability is 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 is onl ...

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 in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

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