Investigation of Metal-H2O Systems at Elevated Temperatures: I. Development of a Solubility Apparatus Specialized for Super-Ambient Conditions

Abstract

Abstract In industrial settings such as nuclear power plants, metals are often subjected to high temperature and pressure aqueous environments, where failure to control corrosion has economic and safety consequences. To extend corrosion modelling tools, such as Pourbaix diagrams, to harsh aqueous conditions, there is a need for experimental thermochemical data performed at elevated temperatures. This is particularly true for metal and alloy systems where such information is unavailable or unreliable. A relatively simple approach to obtaining temperature dependent thermodynamic properties is the investigation of solid-liquid phase, or solubility, equilibria. However, this requires specially designed instrumentation that can withstand harsh temperatures and extreme pH conditions, while providing accurate data. In this work, an apparatus developed for super-ambient highly acidic and alkaline solubility experiments, is presented. The instrumentation and analysis process was validated by examining the solubility of the well-studied zinc oxide system, where the resulting equilibrium data could be compared to literature. A constant volume, batch reactor system with in-situ pH measurement is described along with a brief presentation of the ZnO dissolution equilibria results at 358.15 K.