Electrochemical corrosion of iron-magnesium-alumina spinel (FMAS) in molten potassium salts and coal slag
Iron, magnesium-alumina spinel (FMAS) (0.25 Fe/sub 3/O/sub 4/ . 0.75 MgAl/sub 2/O/sub 4/) has been considered for use as an electrode in magnetohydrodynamic (MHD) generator channels. Predominantly an electronic conductor, FMAS has adequate electrical conductivity (>1 S/m) above 520/sup 0/K. In addition, FMAS can be easily fabricated into a form and sintered in air to >90% theoretical density and has a melting point of 2124 +- 20/sup 0/K. Laboratory tests to measure both the electrochemical and chemical corrosion of FMAS in molten K/sub 2/CO/sub 3/, K/sub 2/SO/sub 4/ and coal slags were developed at the Pacific Northwest Laboratory to evaluate the relative corrosion of FMAS. Under isothermal conditions, a direct electric current was passed between an anode and a cathode through a molten electrolyte. The molten coal slags were synthetic high-calcium, low-iron Montana Rosebud and low-calcium, high-iron Illinois No. 6. Evaluations of electrochemical corrosion were made as functions of current density, temperature, and slag composition. These results were compared to those of FMAS tested without electric current. The corrosion rates and reaction products were investigated by optical microscopy and scanning electron microscopy. Overall, FMAS has too-high an electrochemical corrosion rate to be considered as MHD electrodes in Montana Rosebud coal slag or in systems where only molten potassium salts are present. However, FMAS may be considered for use in high-iron coal slags although the corrosion rates are still quite high even in these slags.
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 6651706
- Report Number(s):
- PNL-3627
- Country of Publication:
- United States
- Language:
- English
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300103* -- MHD Generators-- Materials
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Cermets
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ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBONATES
CHALCOGENIDES
CHEMICAL REACTIONS
COAL-FIRED MHD GENERATORS
CORROSION
CORROSION RESISTANCE
CORROSIVE EFFECTS
DATA
DIRECT ENERGY CONVERTERS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CORROSION
ELECTRODES
EXPERIMENTAL DATA
INFORMATION
IRON COMPOUNDS
IRON OXIDES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MATERIALS
MATERIALS TESTING
MELTING POINTS
MHD CHANNELS
MHD GENERATORS
MINERALS
MOLTEN SALTS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POTASSIUM CARBONATES
POTASSIUM COMPOUNDS
POTASSIUM SULFATES
SALTS
SLAGS
SPINELS
SULFATES
SULFUR COMPOUNDS
TEMPERATURE DEPENDENCE
TESTING
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE