Multidimensional Modeling of Nickel Alloy Corrosion inside High Temperature Molten Salt Systems

Abstract

One challenge with concentrated solar power (CSP) systems is the potential corrosion of the alloys in the receivers and heat exchangers at high-temperature (700–1000°C), which leads to a reduction of heat transfer efficiency and influences the systems durability. In this work, a corrosion model has been developed to predict the rates and mechanisms for corrosion of a nickel-based alloy that is in contact with a molten salt heat transfer system. In addition to accounting for heat and mass transfer effects on the corrosion, the model takes into account the electrochemical kinetics. Coupled with computational fluid dynamics (CFD), the local electrochemical environment and corrosion rates in a high-temperature molten salt system can be predicted. The kinetic, heat and mass transfer parameters used in the model are based on experimental studies conducted in a thermosiphon. The immersion cell was designed to expose coupons to the molten salt at isothermal or non-isothermal conditions between 700–1000°C. The model can predict the effect of thermal gradients between the top and the bottom of the reactor which induce natural convection of the molten salt. The model has been validated against experimental results at different isothermal and non-isothermal conditions and good agreement has been achieved between the model predictions of the corrosion rates and corrosion potentials with the experimental observations.