Corrosion behavior of stainless steel types AISI 316L, 316Ti and 321 was studied at 750 0C in NaCl-KCl equimolar melts. Iron, chromium and manganese species constitute the major corrosion products. The following mechanism of stainless steel corrosion in molten chlorides was proposed: 1) chemical interaction between the alloy and the salt intensified by the formation of microgalvanic pairs; 2) formation of chromium and molybdenum carbide-containing phases in steel as a result of heating to 750 0C; 3) additional formation of galvanic pairs between the grains of austenitic alloys and the carbide phases at the grain boundaries resulting in enhanced intergranular corrosion.

The corrosion behavior of the corrosion-resistant alloy Hastelloy G-35 (manufactured by Haynes International, Inc.), corrosion and heat resistant alloy VDM Alloy 600 or Nicrofer 7216 and corrosion-resistant alloys VDM Alloy C-4 or Nicrofer 6616 and VDM Alloy 625 or Nicrofer 6020 (all produced by VDM Metals) was studied at 450–650 °C in fused KCl–AlCl₃ mixture with the initial AlCl₃-to-KCl ratio of 1.1. Time of exposure varied from 6 to over 1000 h. The corrosion rates of all the nickel-based alloys studied were determined by the red-ox processes resulting in dissolving the most electronegative alloy components (Cr, Fe and Mn) indicating that the processes taking place had electrochemical nature. Increasing temperature led to a noticeable increase of corrosion rates and a change of the corrosion process nature. Transmission electron microscopy revealed that intermetallic phases (such as sigma-phase in case of Hastelloy G-35 and Alloy 625 or Ni₂(Cr,Mo) secondary phase in VDM Alloy C-4) can be formed during prolonged high-temperature exposure. These phenomena can accelerate the processes of intergranular corrosion and stress corrosion cracking of studied materials in industrial conditions. The results obtained agreed well with thermodynamic analysis, mechanical and thermophysical properties of the alloys and constructed "time-temperature-precipitation" diagrams.

The corrosion resistance of Haynes 230, Hastelloy S and X high-temperature alloys and Hastelloy N, B-3, G-35, C-2000 corrosion-resistant alloys was investigated in a wide temperature range (450–650 °C) in fused KCl-AlCl₃ mixtures. It was found that the mechanisms of corrosion of high-temperature alloys and corrosion-resistant alloys in KCl-AlCl₃ based melts are different. At a critical temperature phase structure of the high-temperature alloys changes after contact with chloroaluminate melts resulting in formation of intermetallic or carbon-containing phases along the grain boundaries that result in increasing strength of the alloys but initiate intense intergranular corrosion. The structural changes in most of the corrosion-resistant alloys take place at higher temperatures but they also can cause structural changes in the materials. It was shown that both types of alloys undergo intergranular corrosion up to the critical conditions. Formation of different secondary phases was detected and their influence on the corrosion processes mechanism is analyzed.

High-temperature spectroelectrochemestry was applied to study corrosion of various types of stainless steel in molten salts. The electronic absorption spectra of products of anodic dissolution of stainless steel major components (iron, chromium, nickel, molybdenum, manganese, titanium) were measured in NaCl-KCl melt at 750 °C. The effectiveness and limitations of applying spectroscopic method for studying alloys corrosion was demonstrated on example of anodic dissolution of AISI 316L, 316Ti and 321 austenitic steels. The major corrosion products of steels are iron, manganese and chromium species. Prolongation of anodic dissolution leads to increasing chromium-to-iron ratio in the melt. Titanium in steels forms very stable carbonitride species that aren't dissolved during anodic oxidation.

Corrosion of nickel alloys in molten salts is a complex process dependent on many factors. The paper describes the influence of microstructural changes in several nickel-based alloys (Hastelloy^® G-35^®, VDM^® Alloy 59, KhN62M-VI, Hastelloy^® B-3^®) on the mechanism of their corrosion in molten fluoride salts. The corrosion experiments were performed in LiF–NaF–KF and (LiF–NaF–KF) + UF₄ melts at 550–750 °C. Formation of excess secondary phases along the grain boundaries of the alloys led to heterogeneity of the alloy microstructure. As a result of these changes, microgalvanic couples formed on the surface of the alloys, leading to the development of intergranular corrosion upon contact with molten electrolytes. Secondary phases acted as microanodes or microcathodes depending on a number of factors. Formation and composition of the secondary phases affected the depth and extent of the corrosion damage to nickel alloys.