On the sulfation reaction of protective and transient oxides at 650 °C and its role in the low temperature hot corrosion mechanism

MxOy-Na2SO4 (with M = Ni, Cr, Fe, Al, Ti, Nb) and NiSO4-Na2SO4 mixtures were prepared and their reactivity was examined at 650 degrees C in air + SO2 (400 and 1000 ppm). The formation of a molten phase for NiSO4-Na2SO4 mixtures and the rapid sulfation of NiO in these conditions were demonstrated. NiO sulfation should be considered when explaining the Type II hot corrosion attacks. Cr2O3, Fe2O3 and Al2O3 also react with the gas phase showing these oxides dissolved according to an acidic-fluxing mechanism in air + SO2/SO3 (400 and 1000 ppm) environments. Al2O3 is more soluble than Cr2O3 in these conditions.

Automated summary

MxOy-Na2SO4 (M = Ni, Cr, Fe, Al, Ti, Nb) and NiSO4-Na2SO4 mixtures were prepared and their reactivity at 650 degrees C in air + SO2 (400 and 1000 ppm) was investigated. It was found that a molten phase was formed in NiSO4-Na2SO4 mixtures, and rapid sulfation of NiO occurred under these conditions. The sulfation of NiO should be considered in explaining Type II hot corrosion attacks. Cr2O3, Fe2O3, and Al2O3 also reacted with the gas phase, indicating dissolution of these oxides through an acidic-fluxing mechanism in air + SO2/SO3 (400 and 1000 ppm) environments. Al2O3 exhibited higher solubility than Cr2O3 under these conditions.