Corrosion of Nickel-Containing Alloys in Molten LiCl-KCl Medium

• Published in: Corrosion (Houston, Tex.) Vol. 69; no. 1; pp. 48 - 57
• Main Authors: RAVI SHANKAR, A, KANAGASUNDAR, A, KAMACHI MUDALI, U
• Format: Journal Article
• Language: English
• Published: Houston, TX NACE International 2013
• Subjects: Alloys; Analytical methods; Applied sciences; Breeder reactors; Chloride; Chlorides; Chromium; Chromium oxides; Corrosion; Corrosion environments; Corrosion mechanisms; Corrosion rate; Corrosion resistance; Corrosion resistant alloys; Corrosion tests; Electron microscopy; Exact sciences and technology; Exposure; Fast breeder; Ferrous alloys; High temperature; Lasers; Lithium; Lithium chloride; Metal fuels; Metals. Metallurgy; Molten salts; Molybdenum; Morphology; Nickel; Nickel base alloys; Nickel oxides; Nuclear fuels; Oxides; Potassium; Potassium chloride; Raman spectroscopy; Reprocessing; Salts; Scale (corrosion); Scanning electron microscopy; Spallation; Superalloys; Thin films; X rays; X-ray diffraction; Scanning electron microscopy; super alloys; Temperature; high-temperature corrosion; x-ray diffraction; Lithium chloride; High temperature; Potassium chloride; X ray diffraction; High temperature corrosion
• ISSN: 0010-9312; 1938-159X
• DOI: 10.5006/0627

Pyrochemiccd reprocessing utilizing molten chloride salt has been considered one of the best options for reprocessing of spent metallic fuels of future fast breeder reactors. Materials for pyrochemical reprocessing applications should possess high-temperature strength, corrosion, and scale resistance. The present work discusses the corrosion behavior of Ni-based alloys 600 (UNS N06600), 625 (UNS N06625), and 690 (UNS N06690) and alloy 800H (UNS N08810) exposed to molten lithium chloride-potassium chloride (LiCl-KCl) eutectic salt at 673, 773, and 873 K for 2 h in the presence of air. The corrosion rates of the samples were determined and surface morphology of the exposed samples and scales were examined using scanning electron microscopy (SEM), x-ray diffraction (XRD), and laser Raman spectroscopy (LRS). The results indicated that Ni-based alloys (UNS N06600 and UNS N06690) offer better corrosion resistance compared to Ni-based alloy (UNS N06625) and alloy 800H (UNS N08810) because the presence of Mo in Ni-based alloy (UNS N06625) is not beneficial for molten salt environment in air. Based on the surface morphology, XRD, and cross-sectional energy-dispersive x-ray (EDX) analyses of scales and exposed samples, the mechanism of corrosion of alloys appears to be from the formation of Cr-rich and Ni-rich layers of chromium (III) oxide (Cr sigma ub 2 omicron sigma ub 3 less than or equal to nickel oxide (NiO), and spinel oxides at the surface and subsequent spallation. The paper highlights the results of the present investigation.