Corrosion Of Ceramics Research Articles

Scandia-stabilized zirconia for resistance to molten vanadate-sulfate corrosion

Following an acid-base theory of ceramic corrosion developed at the Naval Research Laboratory, we have identified scandia as a stabilizer potentially more resistant to molten sulfate-vanadate attack than yttria, the commonly used zirconia stabilizer. This prediction is supported in the present work where, for example, scandia-stabilized zirconia (SSZ) gave no detectable reaction or destabilization after 160 h exposure to 900 °C molten NaVO 3, whereas yttria-stabilized zirconia (YSZ) reacted strongly with the NaVO 3 (with YVO 4 formed) and was extensively destabilized. Other tests confirmed the superior resistance of Sc 2O 3 over Y 2O 3 to reaction with both molten sodium vanadate and Na 2SO 4/SO 3. The additional cost for scandia, which is expensive, was calculated to be about $0.15 cm -2 of 10 × 10 -3 in (250 μm) coating, or less than half the cost, e.g. for platinum in current platinum-augmented aluminade coatings. Development of molten sulfate- and vanadate-resistant SSZ coatings could give large savings by allowing cheaper, low quality sulfur- and vanadium-containing fuels to be burned in gas turbine or diesel engines.