One way to potentially reduce the costs of concentrated solar power (CSP) central receiver systems is to operate the central receiver at high temperatures that allow for more efficient thermodynamic power conversion cycles. Molten salts are one potential heat transfer fluid at that can operate efficiently at these temperatures, but their use will introduce other technological challenges, such as corrosion and mass transfer reactions.  The corrosion of alloys at high-temperature (700-1000°C) in the receivers and heat exchangers cause a reduction in heat transfer efficiency and durability. Cathodic protection may mitigate corrosion of metal surfaces by shifting the potential of the alloy below its oxidation potential.  The behavior of molten salt cooled concentrated solar power (CSP) systems under cathodic protection can be obtained by developing a 3-D model. A simplified model was designed for and benchmarked against a  thermosiphon reactor.  This thermosiphon reactor exposed alloy coupons to non-isothermal conditions expected in concentrated solar power (CSP) plants. When the cathodic current density is equal to the protection current density and the potential is a protective, the model calculates the corrosion rate and the corrosion potential. Magnesium was used as a sacrificial anode. The rate of Mg consumption, the corrosion potential, and the corrosion current are dependent on several studied variables. Kinetic parameters were obtained from experimental coupon exposures conducted between 700-1000 °C in molten salt in the thermosiphon reactor.  Results were in good agreement with experimental values at different conditions.

     Fig. 1 shows a comparison of the model prediction of corrosion rate distribution, i (A/cm²) at coupon surfaces for both Hot-Zone and Cold- Zone without (a) and with (b) cathodic protection.

Acknowledgements

The authors gratefully acknowledge the financial support for this work from the DOE EERE SunShot Initiative (DE-AC36-08GO28308) under a subcontract from SRNL to the University of South Carolina. The authors also thank the University of South Carolina Center for Fuel Cells and the CD-adapco group for their support.