Mechanism of metal dusting corrosion by pitting of a chromia-forming alloy at atmospheric pressure and low gas velocity

Aurélien Fabas (1) , Daniel Monceau (1) , Claudie Josse (2) , Pascal Lamesle (3) , Aurélie Rouaix-Vande Put (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 Centre Castaing - Centre de microcaractérisation Raimond Castaing
3 ICA - Institut Clément Ader

FeNiCr samples (800HT) were exposed at 570 °C, 1 bar to a 47.25CO-47.25H2-5.5H2O atmosphere (ac = 33) flowing at 18 μm/s. Pitting corrosion was observed. Pits showed a flattened morphology and a constant pit diameter growth rate. Corrosion rings appeared successively at the surface during pit growth. A four-step mechanism is proposed which includes internal oxidation of carbides, graphitisation and localised enhanced graphitisation. Gas velocity and thermal cycling play key roles in pit morphology. Thermal cycling induces circular cracks. Low gas velocity induces the gas to evolve in crevices, due to local oxygen consumption.

Mots clés: Steel; High temperature corrosion; Carburization; Internal oxidation

Domaines: Matériaux

Aurélien Fabas, Daniel Monceau, Claudie Josse, Pascal Lamesle, Aurélie Rouaix-Vande Put. Mechanism of metal dusting corrosion by pitting of a chromia-forming alloy at atmospheric pressure and low gas velocity. Corrosion Science, 2016, 107, pp.204-210. ⟨10.1016/j.corsci.2016.02.033⟩. ⟨hal-01488950⟩