Corrosion of Fe-(4.8,9.2,14.3) Wt%Al alloys at 700 and 800 A°C in N2/H2O/H2S gases

Fe-(4.8, 9.2, 14.3)wt%Al alloys were corroded at 700 and 800 A degrees C for up to 70 h in 1 atm of N-2/H2O and N-2/H2O/H2S gases. Oxidation prevailed in N-2/H2O gases. Fe-(4.8, 9.2)Al alloys formed a duplex scale that consisted of an outer iron oxide layer and an inner (Fe, Al, O)-mixed layer. The Fe-14.3Al alloy formed a thin layer consisting of alpha-Al2O3. Sulfidation dominated in N-2/H2O/H2S gases, resulting in rapid corrosion. Fe-(4.8, 9.2)Al alloys formed a duplex scale that consisted of an outer FeS layer and an inner (Fe, Al, S, O)-mixed layer. The high growth rate of FeS impeded the formation of a continuous, protective aluminium-rich oxide. The Fe-14.3Al alloy formed a thin layer consisting of alpha-Al2O3 that was incorporated with a bit of sulfur.