Corrosion behavior of metals and alloys in Ionic Liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl)-imide

I&EC 144

Ilaria Perissi, ilaria.perissi@unifi.it1, Stefano Caporali, stefano.caporali@unifi.it1, Ugo Bardi, bardi@unifi.it2, Alessandro Lavacchi1, and Alexander Tolstoguzov1. (1) Chemistry Department, University of Firenze, via della Lastruccia 3, Sesto Fiorentino, 50019, Italy, (2) Dipartimento di Chimica, Universita' di Firenze, Via G. Capponi 9, 50121, Firenze, Italy
This work reports the results of the characterization of the corrosion phenomena occurring in the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl)-imide ([C4mim][Tf2N]). Several of the most common metals and alloys used in thermal and chemical plants have been considered (Copper, Nickel, Brass, AISI 1018, Inconel). The corrosion behavior has been investigated both by electrochemical and gravimetric techniques. Room temperature potentiodynamic curves have been acquired in order to determine the active/passive behavior. The corrosion rates have been determined by extrapolation from Tafel plots and by polarization resistance measurements. Gravimetric measurements have also been performed after the immersion tests carried out for time up to 1000 h in the range of temperature between 150°C up to 325 °C. The morphology of the samples subjected to the tests has been investigated by Scanning Electron Microscopy, showing the occurrence of both uniform and localized corrosion phenomena. The test solution also showed a dramatic coloration change possibly due to the thermal decomposition of the Ionic Liquid. After the immersion tests some of the samples exhibited the formation of a dark brown layer at the surface. The composition of such layer has been investigated by Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy. Compositional surface analysis data provide that such layer is due to both the oxidation of the metal and the thermal decomposition of the IL.