Corrosion Behavior of Yttria-Stabilized Zirconia-Coated 9Cr-1Mo Steel in Molten UCl3-LiCl-KCl Salt

Compatibility of 3D-Printed Oxide Ceramics with Molten Chloride Salts for High-Temperature Thermal Energy Storage in Next-Generation CSP Plants

“…This implies that corrosion of the 3D-printed ZrO 2 ceramic in molten MgCl 2 /KCl/NaCl, as metallic alloys [4,5,7] and C/C-SiC composite [16] caused by corrosive salt impurities like MgOHCl [5], does not occur at 700 • C under Ar atmosphere. This observation is supported by the literature [11,12] and the result of our thermodynamic simulations with the commercial software FactSage, which was used for a corrosion mechanism study of a C/C-SiC composite in our previous work [16], finding that the reactions of ZrO 2 and Y 2 O 3 with HCl (decomposition product of MgOHCl at >555 • C [6,27]) have a positive ∆G • of 156-182 and 88-208 kJ/mole at 500-900 • C, respectively (see Equations ( 5) and ( 6 (5) Y2O3 (s) + 6HCl (g)↔2YCl3 (l) + 3H2O (g) ∆G° = +(88-208) kJ/mole (500-900 °C) (6) Al2O3 (s) + 6HCl (g)↔2AlCl3 (g) + 3H2O (g) ∆G° = +(321-323) kJ/mole (500-900 °C) (7) Al2O3 (s) + 3MgCl2 (g)↔2AlCl3 (g) + 3MgO (g) ∆G° = +(11-78) kJ/mole (500-900 °C) (8) Al2O3 (s) + 3MgCl2 (l)↔2AlCl3 (g) + 3MgO(g) ∆G° = +(310-231) kJ/mole (500-900 °C) (9) Figure 7. SEM-EDX images of the cross section of ZrO2 samples before (left) and after (right) molten salt exposure.…”

“…Thus, the transformation of the metastable tazheranite T phase to the thermodynamically stable baddeleyite M phase should be attributed to the presence of the molten MgCl 2 /NaCl/KCl salt-that is, molten salt treatment could have a beneficial effect on the T→M transformation. It was reported in [11] that the M↔T phase change in a 8-9 wt.% Y 2 O 3 -stabilized ZrO 2 coating was not observed after 2000 h exposure in molten LiCl-KCl-UCl 3 (5-6 wt.%) salt (mainly alkali metal chlorides) at 600 • C under argon atmosphere. Based on this finding, the aforementioned results from the phase diagrams of ZrO 2 stabilized with Y 2 O 3 and MgO and the calculated ∆G • values with FactSage in Equations (1-4), the reaction of the Y 2 O 3 -stabilized ZrO 2 with MgCl 2 (mainly Y 2 O 3 and ZrO 2 with gaseous MgCl 2 ) may be the main reason for the T→M transformation.…”

“…The ceramics generally have a better chemical compatibility with corrosive media like molten salts than metallic materials [10]. Yttria-stabilized zirconia (YSZ) ceramic coatings on alloys have demonstrated resistance to the hot corrosion of molten chlorides like LiCl-KCl at high temperatures [11,12]. For instance, Jagadeeswara Rao et al showed that 8-9 wt.% yttria-stabilized zirconia (YSZ) ceramic coating on an alloy was corrosion resistant to molten LiCl-KCl-UCl 3 (5-6 wt.%) salt at 600 • C under argon atmosphere in a 2000 h molten salt exposure test [11].…”

“…Yttria-stabilized zirconia (YSZ) ceramic coatings on alloys have demonstrated resistance to the hot corrosion of molten chlorides like LiCl-KCl at high temperatures [11,12]. For instance, Jagadeeswara Rao et al showed that 8-9 wt.% yttria-stabilized zirconia (YSZ) ceramic coating on an alloy was corrosion resistant to molten LiCl-KCl-UCl 3 (5-6 wt.%) salt at 600 • C under argon atmosphere in a 2000 h molten salt exposure test [11]. Thus, the oxide ceramics are often used for molten chloride laboratory experiments (e.g., corrosion, electrochemistry, crucibles) [10,13].…”