For the design of high-temperature devices for the developed technology for high-temperature reprocessing and subsequent regeneration of spent nuclear fuel, it is necessary to select corrosion-resistant materials and a set of measures to reduce the corrosion rate in molten salts. Nickel-chromium alloys alloyed with refractory metals are highly resistant to both corrosion in low-temperature electrolytes and gas corrosion at high temperatures [1–7]. That is why Hastelloy-type alloys are traditionally considered promising for the creation of parts for nuclear and chemical reactors, containers with toxic waste, as well as valves and pipes for chemical production. The aim of this work is to study the process of corrosion of metallic materials, the characteristics of the process of corrosive electrochemical interaction in the system alloy – melt of alkali metal salts, containing additives of trichlorides of f-elements. The object of investigation is a system formed by a melt of a eutectic mixture of lithium and potassium chlorides with the addition of 0.5–2 wt % LaCl3, CeCl3, NdCl3, imitating uranium and plutonium compounds, in the temperature range of 500–650°С. Hastelloy C-4 alloy was used as the test material. Atmosphere above the melt: Ar + 10% O2. Research methods: gravimetric, chemical-analytical (atomic absorption). To analyze the products, an X-ray microspectral research method was used. It is shown that oxygen-containing compounds of complex composition based on nickel(II) oxide and lanthanide oxychlorides are formed on the surface of the alloy under study, which retard the corrosion of the material as shielding inhibitors.