Molten Salt Corrosion of Stainless Steels and Low-Cr Steel in CSP Plants

• Published in: Oxidation of metals Vol. 78; no. 5-6; pp. 329 - 348
• Main Authors: Fernández, A. G., Lasanta, M. I., Pérez, F. J.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.12.2012; Springer
• Subjects: Applied sciences; Chemistry and Materials Science; Corrosion; Corrosion and Coatings; Corrosion environments; Exact sciences and technology; Inorganic Chemistry; Materials Science; Metallic Materials; Metals. Metallurgy; Original Paper; Tribology; Concentrated solar power plants; Corrosion; Differential scanning calorimeter; Molten salt; Electric power plant; Stainless steel; Salt corrosion; Solar energy; Oxidation; Application; Fused salt corrosion; Molten steel
• ISSN: 0030-770X; 1573-4889
• DOI: 10.1007/s11085-012-9310-x

The corrosive effects of 60 % NaNO 3 /40 % NaNO 3 have been tested at 390 and 550 °C, in order to simulate the working conditions in two principal concentrated solar power (CSP) plants, on stainless steel (AISI 304, 430) and on a low-Cr alloy steel (T22) containing 2.25 % Cr. The corrosion rates were determined by gravimetric tests, measuring the weight gain during 2,000 h, identifying the corrosion products via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Thereby, Fe 2 O 3 and Fe 3 O 4 were the most prominent products formed from the tests performed at 390 °C, being observed also the formation of some stable compounds due to the impurities of the salt, as magnesium ferrite (MgFe 2 O 4 ) and NaFeO 2 . The study at 550 °C of stainless steels revealed a better behavior under corrosive environments than T22 steel, identifying the formation of FeCr 2 O 4 protective spinels mainly. To complete the corrosion tests, thermo-physical studies were carried out in binary mixture, using DSC and TGA. Also the most important parameters of the salt before and after corrosion test were tested.