The reaction of water vapor with metals or metal oxides to form volatile hydroxides at elevated temperatures is an important mechanism of corrosion in combustion environments. We are studying the reaction of zinc oxide with water vapor in the temperature range 600-900°C. Zinc oxide is placed in a quartz transpiration apparatus and a flowing stream of inert gas and water vapor is passed over the sample. Volatile zinc hydroxide species are transported downstream and collected in the cooler collection tube for analysis. Variation of the partial pressure of water vapor allows the determination of the vaporizing species. Measurements over a range of temperatures will permit determination of the enthalpy for the reaction at the average temperature of the experiments. Initial results will be discussed.