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The study explores the corrosion mechanisms and kinetics that are related to materials dissolution, oxidation, and diffusion of Ni-based alloys (Hastelloy N and Hastelloy X) and Fe-based alloy (SS316) in molten fluoride salt (LiF-NaF-KF, known as FLiNaK) at 750 °C for various exposure times in Ni crucibles. These three alloys were chosen to study the effects of kinetics and corrosion of major constituents commonly found in materials such as Ni, Fe, and Cr. FLiNaK salt and its oxygen concentrations were characterized before and after tests. The results showed Cr2O3 formation and dissolution in higher Cr alloys (SS316 and Hastelloy X) but not in low Cr alloys (Hastelloy N). The diffusion rate of Cr from the bulk limits the corrosion at alloy/salt interface in the low Cr alloy. In the high Cr alloys, Cr2O3 formation and dissolution dominate the initial oxidation (1 day), while Cr2O3 formation and dissolution continue to dominate the oxidation in higher Cr alloys. However, Cr diffusion to alloy/salt interface eventually governs the processes for long-term exposure (21 days) due to the instability of oxides in molten salt. [ABSTRACT FROM AUTHOR]

Corrosion of aluminum alloy 1100 exposed to the boron‐containing alkaline solutions was studied. Test solutions were in the pH 7.5–8.2 range at 25, 55, and 85 °C. Both post‐tested aluminum alloy and alkaline solution were analyzed to characterize corrosion. The results indicate that the oxide layer at 25 and 55 °C was gibbsite Al(OH)3, and at 85 °C was boehmite AlOOH. Colloid deposits were found on the sample surface at 85 °C because of the phase transition of dissolved corrosion products with aging. The physics‐based aluminum release model for each test condition was developed to simulate the progression of aluminum concentration in the solution. Based on the model, the mass transfer coefficient of each test condition can be obtained. [ABSTRACT FROM AUTHOR]

• Corrosion and precipitation behavior of aluminum alloy in H 3 BO 3 , NaTB and TSP solutions at high temperatures were studied. • The phase transition of aluminum hydroxide preferentially occurs in NaTB solution. • Zinc inhibits the aluminum corrosion more effectively than fiberglass. • Kinetic equation is developed to describe Al loss as a function of mass transfer coefficient and solution pH. • The aluminum alloy suffers severe corrosion and precipitation in strong alkali solution. The aluminum (Al) alloy corrosion and precipitation tests were carried out in a high-temperature flow loop under different hypothesized post-LOCA chemistry conditions. The effect of the temperature, pH, flow rate and presence of other potential ions on Al corrosion was studied. The Al hydroxide phase transition from less-stable forms to thermodynamically stable forms during isothermal stage preferentially occurred in NaTB-buffered solution. The presence of Zn in solution could effectively inhibit Al release. The solution pH has a strong influence on Al corrosion and the volume of formed precipitate. A kinetic equation was developed to describe Al loss as a function of mass transfer coefficient and solution pH, the effect of OH- concentration on Al corrosion was more pronounced than the rate of mass transfer. [ABSTRACT FROM AUTHOR]

• Corrosion of alloy 230 in molten KCl-MgCl 2 -NaCl salt was impurity driven. • Corrosion due to molten salt vapors was more severe. • The corrosion process was driven by intergrannular corrosion. • Magnesium in the molten salt intensified corrosion in alloy 230 due to Mg-Ni interaction. The impurity-driven corrosion behavior of HAYNES ® 230 ® alloy in the molten KCl-MgCl 2 -NaCl salt was studied at 800 °C for 100 h with different salt purity conditions. It was found that HAYNES ® 230 ® alloy exhibited better corrosion resistance in the salt with lower impurities. Furthermore, the corrosion (non-immersion) due to molten salt vapors was more severe at higher temperature. The attack was localized and driven by outward diffusion of chromium through the grain boundaries. The presence of Mg in its metal form in the salt resulted in an even higher mass-loss in HAYNES ® 230 ® alloy due to Mg-Ni interaction. [ABSTRACT FROM AUTHOR]