Effects of cerium and manganese on corrosion of Fe–Cr and Fe–Cr–Ni alloys in Ar–20CO2 and Ar–20CO2–20H2O gases at 650 °C

Sulfur Effect on Corrosion Behavior of Fe-20Cr-(Mn, Si) and Fe-20Ni-20Cr-(Mn, Si) in CO2-H2O at 650°C

“…No carburization was observed in Fe-20Cr-0.5Si alloy exposed to sulfur-free wet CO 2 gas. 18 The Fe-20Cr and Fe-20Cr-0.5Si alloys exposed to SO 2 -containing gas developed only intergranular carbides (Figs. 8c and 8d), lying deeper within the alloy below the intergranular sulfide (Fig.…”

“…13d) The Fe-20Cr-20Ni-0.5Si alloy partially developed a thin scale which was frequently interrupted by iron oxide scale when exposed to wet CO 2 gases in the absence of SO 2 . 18 The apparent fluctuations in weight uptakes are due to random variations in the nucleation of iron oxide nodules on different alloy specimens. No scale spallation was observed on this Si-containing alloy in wet CO 2 gas.…”

“…The beneficial effect of Si addition is due to the formation of an SiO 2 scale which acts as a diffusion barrier. 18 However, the addition of 0.5% Si had no significant improvement on the corrosion kinetics for Fe-20Cr-20Ni alloy in sulfur-free wet CO 2 gas (Fig. 9), and breakaway oxidation occasionally occurred on both the undoped and Si-doped alloys.…”

“…Carburization was suppressed in Si-bearing alloys in sulfur-free gas, with no carbide formation in the Fe-20Cr-0.5Si alloy. 18 This phenomenon was explained by the formation of an additional, continuous silica layer which blocks carbon penetration and carburization underneath the scale. However, in the presence of sulfur, very limited intergranular carbides were identified (Fig.…”

“…The critical Si content to maintain the growth of a continuous silica layer is: [5] where k S is the parabolic rate constant for silica layer thickening. These calculations have been carried out, 18 yielding N −3 for the austenitic alloy in sulfur-free wet CO 2 gas, the actual Si level (9.8 × 10 −3 ) in Fe-20Cr-20Ni-0.5Si is marginal for silica layer maintenance. Thus more Si may be required for enhanced corrosion resistance of this alloy in wet CO 2 gas.…”