Corrosion Behavior of Two Kinds of Stainless Steels in a Novel Ternary Nitrate/Nitrite Molten Salt

ABSTRACT The corrosion behavior of 316 L stainless steel (316 L) and 347 stainless steel (347) at 500°C in a novel molten salt (KNO 3 –NaNO 2 –KNO 2 , KNK) is investigated. The corrosion behavior is determined by recording the weight changes of the stainless steels at different time intervals and analyzing the KNK compositional changes before and after corrosion, combined with changes in the morphology and intrinsic characteristics of the stainless steels. X‐ray diffraction (XRD) and inductively coupled plasma mass spectrometry are employed to characterize the phase and component of KNK; XRD, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy are used to characterize the composition, morphology and microstructure of the corrosion products on the surface. Analyses of the changes in KNK composition before and after corrosion, as well as the surface morphology and composition of the stainless‐steel sheets, show that the corrosion product of 347 is more prone to Fe 3 O 4 , whereas the corrosion product of 316 L is more prone to Fe 2 O 3 . Fe 3 O 4 formation devitalizes the corrosion reactions to some extent; consequently, 347 exhibits stronger corrosion resistance than 316 L.