High-Temperature Corrosion, Corrosion Mitigation, and Materials Durability Improvement for Hydrogen Production
LaboratorySavannah River National Laboratory (SRNL)
Capability ExpertBrenda L. Garcia-Diaz
Node Readiness Category3: Hybrid Thermochemical (HT)
3: High-Temperature Electrolysis (HTE)
This capability consists of characterizing corrosion in high temperature systems and identifying methods to mitigate corrosion in the high temperature systems. SRNL has furnaces and reactors that can operate at temperatures up to 1200 °C for immersion testing, a thermosiphon for testing corrosion in systems with flow, and electrochemical cells to provide additional characterization methods for corrosion reactions and corrosion mitigation. SRNL has used a variety of external vessels, including stainless steel, Inconel, and quartz for use with different chemical environments including molten chlorides, molten fluorides, and high-temperature steam. The gas environment in the systems can be controlled to accurately simulate different operational scenarios. Crucibles made with materials including alumina, pyrolytic boron nitride, and vitreous carbon have been used for compatibility with different solutions and flow-through cells have also been used. SRNL has utilized physical vapor deposition (PVD) and galvanic deposition for creating coatings for preventing material degradation. SRNL also utilizes gloveboxes and glove bags for handling air-sensitive materials used in preparing tests. These capabilities have been used for examining corrosion in high-temperature solar thermal heat transfer systems using molten salts which have been for thermal storage using latent heat or thermochemical reactions. They have also been used for examining coatings for accident tolerant fuel or other applications. Improved materials durability has been achieved through the proper application of chemistry, physics, and materials science using these capabilities.
The furnaces used for high-temperature testing are limited to 1200 °C. Pressures in high temperature cells are limited to below 15 psig with the exception of Parr reactors that can go up to 290 bar at 600 °C. The maximum vessel diameter is 6 inches. Electrochemical testing is limited to +/- 10 V and 5A.
The high-temperature materials degradation facilities enable a high degree of control for testing novel systems. The ability to handle air sensitive materials and couple that with corrosion characterization methods has led to the ability to identify corrosion degradation mechanisms and corrosion rates as well as evaluate mitigation methods. The availability of a variety of testing vessels and setups allows for tailored tests to be configured quickly. In addition, the high-temperature electrochemical testing capabilities exceeding 1000 °C were described by a SunShot program manager as being unique among the groups performing corrosion research that he had been involved with. SRNL also has co-located SEM/EDS capabilities, XRD, and scratch testing. Analytical laboratory testing for molten salt composition, metals composition, and a variety of other tests can also be performed by SRNL analytical laboratories.
SRNL currently has 2 large dual zone vertical furnaces, 1 medium vertical furnace, 1 multi-sample horizontal furnace, 4 high current potentiostat channels with EIS.
The high-temperature corrosion characterization and mitigation efforts at SRNL led to the identification of Mg as a corrosion inhibitor in MgCl2-KCl and FLiNaK. The combination of Mg and MgCl2-KCl is now a leading candidate for corrosion control in the heat transfer systems in concentrating solar power (CSP) applications. Both MgCl2-KCl and FLiNaK are being investigated as high temperature heat transfer fluids that could be used in systems for high temperature electrolysis or thermochemical cycles. Initial tests at SRNL have demonstrated the effectiveness of MAX phase coatings applied by PVD at preventing corrosion in molten salts for CSP systems. Also, the synthesis of MAX phase coatings using PVD has also been shown to mitigate material degradation for Zr cladding exposed to high temperature steam at 1200 °C and enable systems to meet INL targets for oxidation of cladding exposed to Loss-of-Cooling Accident (LOCA) conditions. PVD coatings of MAX phases, refractory alloys, or other materials are one of the methods of corrosion mitigation for high temperature electrolyzers and thermochemical cycles that can be investigated using the capabilities at SRNL.
Image of furnaces and cells for corrosion testing in the Energy Materials Testing Laboratories (EMRL) at SRNL.
L. Olson, R. Fuentes, M. Martinez-Rodriguez, J. Ambrosek, K. Sridharan, M. Anderson, B. Garcia-Diaz, J. Gray, T. Allen, "Impact of Corrosion Test Container Material in Molten Fluorides"; Journal of Solar Energy Engineering: Including Wind Energy and Building Energy Conservation. Vol. 137, Dec. 2015.
D Hyun-Seok Cho, J. W. Van Zee, Sirivatch Shimpalee, Bahareh A. Tavakoli, John W. Weidner, Brenda L. Garcia-Diaz, Michael J. Martinez-Rodriguez, Luke Olson, and Joshua Gray. "Dimensionless Analysis for Predicting Fe-Ni-Cr Alloy Corrosion in Molten Salt Systems for Concentrated Solar Power Systems." Corrosion. June 2016.
L. Olson, R. Fuentes, M. Martinez-Rodriguez, B. Garcia-Diaz, J. Gray, "Reducing Agent Effects on Haynes-230 in Molten Halide Salts"; Transactions of the American Nuclear Society, Vol. 110, Reno, Nevada, June 15–19, 2014, pp. 859-862.