AbstractThis study investigates the corrosion of Hastelloy‐N and Hastelloy‐G35 alloys in an environment of vapors generated from FLiNaK (LiF–NaF–KF: 46.5–11.5–42.0 mol%) salt in an argon and partial (5%) oxygen at 800°C for 48 h. The result of the experiment showed that Hastelloy‐N and Hastelloy‐G35 experienced corrosion in the salt vapor/oxygen environment, causing an increase in the final weight of the samples. The corroded layer had fluorides and oxygen‐bearing compounds in the Hastelloy‐N samples, and oxide‐containing compounds in the Hastelloy‐G35 samples. The elemental mappings of the surface area, of a line across the surface (line scan) and of a cross‐section of the Hastelloy‐N samples showed Mo‐deficient areas and Mo‐rich areas, which reacted differently with the corrosive environment in the case of Hastelloy‐N samples. On the other hand, the elemental mappings of Hastelloy‐G35 samples showed a significant amount of chromium and iron oxides, as chromium had diffused out to the surface and reacted preferentially with oxygen (rather than fluoride) to form part of the corroded layer.