Solubilities of and Fe 04 in Fused Na SO, at 1200 K

The solubility of mixed a-Fe203 and Fe304 in fused NaxSO4 was measured at 1200 K as a function of the melt basicity at 2.14 • 10-7 atm 02. At lower Pox, in separate ranges of basicity where either Fe304 or else FeS is the stable phase, the solubilities of these compounds in Na2SO4 were determined. From these solubility measurements, the activity coeffi-cients of NaFeO~, FeS, and FeSO4 in fused NaxSO4 were calculated to be 430, 180, and 0.83, respectively. On this basis, the solubilities of the iron oxides a-Fe203 and Fe304 and the dominant acidic and basic solutes were calculated for the entire regimes of Pox and melt basicity in which these phases are stable in NaxSO4. Hot corrosion occurs at high temperatures in oxidizing environments when a molten salt deposit contacts ametal surface. Hot corrosion by molten Na2SO4 can cause significant damage in gas turbine and other combustion-product environments. Metal oxides are often the stable phases in contact with fused NaxSO4. Therefore, a knowl-edge of the solubility behavior of metal oxides in molten Na~SO4 should assist in understanding hot corrosion pro