Task 6.7.2 - Improved Corrosion Resistance of Alumina Refractories

In order to increase the efficiency of advanced coal-fired power systems, higher working, fluid temperatures must be reached. To protect some system surfaces, they are covered with corrosion-resistant refractories. Corrosion is the degradation of material surfaces or grain boundaries by chemical reactions with melts, liquids, or gases, causing loss of material and, consequently, a decrease in strength of the structure. In order to develop methods of reducing corrosion, the microstructure that is attacked must be identified along with the mechanism and rates of the attack. Once identified, methods for reducing corrosion rates can be developed. In order to determine the reactivity of a refractory to a slag, several tests have been developed. The most common are the cup slag test, drip slag test American Society for Testing and Materials ([ASTM] C768), gradient slag test, rotary slag test (ASTM C874)and the dip-and- spin test. Among these tests, the cup slag test is the only static test method and the most commonly used. Previous static testing at the University of North Dakota Energy & Environmental Research Center (EERC) has shown that alumina-based castable refractories are among the least expensive and most corrosion-resistant materials for the highest-temperature coal-fired power system applications.