Journal of Industrial and Engineering Chemistry, Vol.1, No.1, 42-48, December, 1995
Fluxing of Iron Oxide by Molten Salt in the Chlorine Containing Environment
Hot corrosion is a type of accelerated metal wastage frequently found in industrial applications especially waste incinerators and fossil-fuel burning boilers. To study the corrosion behavior in real practice, the laboratory tests have been performed. The effect of the temperature, amount of the mixed salt, potentials of oxygen, sulfur oxides(SO2 and SO3, HCl, and water vapor have been studied by Thermogravimetric analysis(TGA) method in the temperature range of 530 and 650℃. The reaction kinetics follow the parabolic rate law for both O2-SO2-SO3 and O2-SO2-SO3-HCl-H2O environments, while it obeys the linear rate law in O2-SO2-SO3-HCl mixture. Corrosion products were characterized by X-ray diffraction, Scanning electron microscopy and Energy dispersive X-ray analysis.
Sulfate induced accelerated attack of low carbon steel in chlorine contaminated environment, occurs by (i) acidic fluxing-the sulfation of the iron oxides to form Fe2(SO4)3, and (ⅱ) vapor phase transfer-vaporization of iron chlorides, FeCl2 and FeCl3, through the oxide scale if PCl2 is high enough to form metal chlorides. Chlorine reacts with salt deposit and iron oxide to produce alkali chlorides and form a complex Na2SO4-K2SO4-Ma3Fe(SO4)3-NaCl-KCl-FeCl2 salt. When the water vapor is added to the dry gas mixture containing HCl, chlorine potential, PCl2, decreases significantly. Below the equilibrium chlorine potentail to form condensed iron chlorides, no vapor phase transfer occurs.
Sulfate induced accelerated attack of low carbon steel in chlorine contaminated environment, occurs by (i) acidic fluxing-the sulfation of the iron oxides to form Fe2(SO4)3, and (ⅱ) vapor phase transfer-vaporization of iron chlorides, FeCl2 and FeCl3, through the oxide scale if PCl2 is high enough to form metal chlorides. Chlorine reacts with salt deposit and iron oxide to produce alkali chlorides and form a complex Na2SO4-K2SO4-Ma3Fe(SO4)3-NaCl-KCl-FeCl2 salt. When the water vapor is added to the dry gas mixture containing HCl, chlorine potential, PCl2, decreases significantly. Below the equilibrium chlorine potentail to form condensed iron chlorides, no vapor phase transfer occurs.
- Kofstad P, High Temperature Corrosion, pp. 465-510, Elsevier, New York (1988)
- Lai GY, High Temperature Corrosion of Engineering Alloys, pp. 145-168, ASM, Materials Park (1990)
- Reid WT, Corey RC, Cross BJ, Trans. ASME, 67, 279 (1945)
- Reid WT, External Corrosion and Deposites, Elsevier, pp. 145-149, New York (1971)
- Barrett RE, Hummell JD, Reid WT, Trans. ASME J. Eng. Power, 88, 165 (1966)
- Levey A, Merryman EL, Trans. ASME J. Eng. Power, 88, 374 (1966)
- Bishop RJ, J. Inst. Fuel, 51, 51 (1968)
- Shi L, Zhang Y, Shih S, Oxid. Metals, 38(5-6), 385 (1992)
- McNallan MJ, Niemczura Z, Lu HH, Park YS, Corrosion/93, Proc. of '93 NACE Annual Meeting, Paper No. 252 (1993)
- McNallan MJ, Thongtem S, Liu JC, Park YS, Shyu P, J. De Physique, Colloque C9, Suppl. J. De Physique III, 3, 143 (1993)
- Halstead WD, Raask E, J. Inst. Fuel, 42, 344 (1969)
- Otsuka N, Natori A, Kudo T, Imoto T, COrrosion/93, Proc. of'93 NACE Annual Meeting, Paper No. 289 (1993)
- Nakagawa N, Isozki T, Corrosion/94, Proc. of'94 NACE Annual Meeting, Paper No. 177 (1994)
- Lee SY, McNallan MJ, J. Electrochem. Soc., 137(2), 472 (1990)
- Gaskell DR, Introduction to Metallurgical Thermodynamics, 2nd ed., p. 586, MacGarw-Hill, New York (1981)
- Lee SY, McNallan MJ, Corrosion, 47(11), 868 (1991)
- Akopov EK, Berman AC, Zh. Neorg. Khim., 4, 1159 (1959)