Proposed Metal Dusting Mechanism in Lower Temperature, High Steam Syn Gas

Aggressive metal dusting attack of nickel-based alloys was encountered in a high steam containing syn gas application at 1050^oF (566^oC).  Metallurgical analysis of the corroded samples revealed enrichment of oxide forming elements, such as chromium and aluminum, at the corroding surface.  However, the corroding base metals were essentially free of carbon ingress contrary to the industry accepted metal dusting mechanism.  The current findings indicate a different corrosion mechanism exists at lower temperatures and high oxygen partial pressures involving spallation of non-protective spinel-like oxides via catalytic carbon deposition at the base metal-oxide interface.  Metallurgical evidence and thermodynamic calculations support this proposed mechanism are described herein.