Study of the corrosion of different alloys in molten carbonate salts by electrochemical impedance spectroscopy

In the present work the corrosion behavior of different alloys (AISI 304, A ISI 430 and TiAl6V) in molten carbonates at 650EC are compared. By using th e Electrochemical Impedance Technique different corrosion parameters such a s the corrosion rate and the oxyde concentration and others features of the different layers of corrosion products are "in situ" determined. Take into account, the corrosion product characterization by X-ray Diffraction (XRD) , Scanning Electron Microscopy (SEM) and Electrochemical impedance Spectros copy (EIS) a corrosion mechanism for every tested alloy is proposed. In all cases, the corrosion mechanisms during the first hours are similar to a hi gh temperature oxidation mechanism. When the equilibrium is established, th e lithiation began by the formation of different double-layers on the surfa ce of Li-metal oxydes. At the end of the corrosion process, one or two inne r layers of metallic oxydes and one or two outer layers of Li-metal oxydes were formed. The corrosion mechanisms of the stainless steels (AISI 304 ans AISI 310S) are a function of their chromium contents. TiAl6V alloy showed the best behavior against the corrosion of molten carbonates by the formati on of a protective layer of mixed Li-Ti oxydes.