Hot corrosion study of coated separator plates of molten carbonate fuel cells by slurry aluminides

• Published in: Surface & coatings technology Vol. 161; no. 2; pp. 293 - 301
• Main Authors: Pérez, F.J, Duday, D, Hierro, M.P, Gómez, C, Agüero, A, Garcı́a, M.C, Muela, R, Sanchez Pascual, A, Martinez, L
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 02-12-2002; Elsevier
• Subjects: Alloys; Applied sciences; Coating; Corrosion; Corrosion environments; Electrochemical impedance spectroscopy; Exact sciences and technology; Fuel cell; Hot corrosion; Metals. Metallurgy; Molten carbonate; Coating; Hot corrosion; Molten carbonate; Fuel cell; Alloys; Electrochemical impedance spectroscopy; Austenitic stainless steel; Scanning electron microscopy; Electrochemical method; Stainless steel-310; Aluminium; Steel; Experimental study; Coatings; X ray diffraction; Molten salt; Corrosion; Carbonates; Slurries
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/S0257-8972(02)00417-6

The corrosion behavior of Al coated AISI 310S stainless steel by slurry and ion vapor deposition (IVD) was investigated as an electrolyte seal material in a mounted carbonate fuel cell (MCFC) at 650 °C. The results were compared with uncoated AISI 310S stainless steel and TA6V alloy. The characterization of the samples after exposure to the eutectic 62 mol.% Li
2CO
3–38 mol.% K
2CO
3 mixture at 650 °C up to 1000 h has shown the presence of LiAlO
2 (coated samples), LiFeO
2 and LiCrO
2 (stainless steels), and Li
2TiO
3 (TA6V) oxides at the scale–melt interface. The electrochemical impedance spectroscopy (EIS) technique has shown high values of polarization resistances for TA6V and lower values for coated steels. The uncoated AISI 310S stainless steel have shown the lowest polarization resistance. A mechanism for the corrosion of Al-coated stainless steels in molten carbonate is proposed taking into account thermodynamic simulations, X-ray diffraction (XRD), scanning electron microscopy (SEM) characterizations, and EIS results. This proposed mechanism confirms that a slurry aluminide coating is able to improve the stainless steel behavior in molten carbonate. However, the TA6V titanium alloy is the most resistant material in molten carbonate but the Al-coated stainless steels appear as the best lifetime-cost compromise.