Coke formation in metal dusting experiments

Selected samples of carbonaceous deposit from metal dusting corrosion have been investigated. The morphology and the internal structure were examined by light microscopy, environmental scanning electron microscopy, and energy -dispersive analysis of X-rays. Alternating structures within the carbonace ous deposits have been observed, which suggest that metal dusting is an osc illatory corrosion process. The results are discussed in the light of repor ted examples of oscillatory high-temperature reactions. Nonequilibrium phas es have been observed, and it is speculated on their origin and influence o n metal dusting. The localized character of this corrosion type is emphasiz ed. Conclusions about the influence of oxygen in the mechanism of metal dus ting are given, leading to the idea of alternating carburizing and oxidizin g conditions occurring in the metal dusting process.