The Molten Salt Corrosion Lab is focused on understanding the corrosion of high temperature molten chloride and fluoride salts for applications in molten salt thermal storage and next generation molten salt cooled nuclear reactors. Molten salt corrosion is highly dependent on the concentration of impurities in the salt, so all experiments take place inside gloveboxes with highly controlled inert argon atmospheres. The lab has 4 gloveboxes for this purpose, equipped with either drop-in or front opening furnaces. The drop-in well furnaces reside below the gloveboxes and have external heating and feedthroughs, so during long term corrosion tests additional work can still be performed in the glovebox.
Current Projects
Optical Basicity for Halide Salts
Much like pH for water, the concentration of free halide ions in molten salts, known as basicity, can greatly affect corrosion behavior. However, there is no direct means of measurement for the optical basicity and no set of standards to use for correlation. This project seeks to construct an optical basicity scale and standard to quantitatively determine the effect of salt composition on structural material corrosion.
For this project, Kailee Buttice has coupled a UV-vis spectrometer with her glovebox for in-situ measurements of salts doped with metal probe ions in her custom furnace.
Molten Salt Loop Experiments
In collaboration with TerraPower, this project seeks to study corrosion of chloride salts (e.g. NaCl – MgCl2 eutectic) on SS316 and Alloy-625. In experiments, a section of tube is irradiated with 16 MeV protons, producing radioisotope markers of different elements in the alloys. The tube section is then welded into the hot leg of the natural convection salt loop, and the activity of the radionuclides can be tracked through different sections of the loop. This provides in-situ data on the attack depth and on the mass transport and deposition of the corrosion products.
Molten Salts for Thermal Storage
Due to their their low melting points, high-temperature stability, good thermal conductivity, low viscosity, and excellent heat transfer characteristics, molten salts are seen as a great candidate for thermal batteries for concentrated solar power (CSP). As such, the corrosion of chloride salts containment vessels and in heat exchangers needs to be well-understood. This project aims to characterize the behavior of a suite of potential materials (alloys, ceramics, and ceramic composites) due to corrosion of a MgCl₂-KCl-NaCl eutectic.
High Throughput Molten Salt Corrosion
Compositionally complex alloys (CCAs) have shown significant promise for advanced materials applications, partially due to their enhanced corrosion resistance. A high throughput technique for evaluating corrosion resistance was developed combining additive manufacturing and salt droplet corrosion tests with a specially engineered probe electrode. This data was used to train a machine learning algorithm to predict corrosion behavior in untested areas of the compositional space, as well as uncover correlations among measured and simulated material properties.
Molten Salt Spectroscopy and Purification
Since corrosion of molten salts is driven principally by impurities in the salt, high purity salts are required for controlled experiments. MaDCoR has a walk-in fume hood equipped for hydro-fluorination purification of fluoride salts, as well as a vacuum purifier that can be used for chloride and fluoride salts. Additionally, the lab is equipped with a UV-vis spectrometer and a Laser Induced Breakdown Specrometer (LIBS) for composition measurement.