Development of a Coal Ash Corrosivity Index for High Temperature Corrosion

Current development of Advanced Steam Cycle coal-fired power plants requires superheater and reheater tubing alloys which can withstand severe conditions for high temperature corrosion. A corrosion equation to predict corrosion rates for candidate alloys has been developed by a study of deposits removed from steam generator tubes and from test probes installed in a boiler, supplemented by laboratory studies using synthetic coal ash. The corrosion equation predicts corrosion for a particular coal as a function of its content of sulfur, acid-soluble alkalies, and acid-soluble aklaline earths. Good agreement was obtained between the corrosion equation and 6000-hour tests using probes of TP347H and 17-14 CuMo.