Room temperature electrochemistry results. Corrosion studies in ethyl-dimethyl-propyl-ammonium bis(trifluoromethylsulfonyl)imide in view of its application as diathermal fluid. U. Bardi, S. Caporali, A. Lavacchi, I. Perissi Chemistry Department, Università di Firenze, via della Lastruccia, 3 - 50019 Sesto Fiorentino - Italy Introduction. P.M. 396.37 Density 1.41 g cm-3 Ionic Liquids experienced a rising interest as fluids for heat exchange and storage because they match most the requirements for thermal application fluids. We chose ethyl-dimethyl-propyl-ammonium bis(trifluoromethylsulfonyl)imide, EdMPNTf2N, (viscosity 71.63 mm2s-1 @ 20°C, Tdec close to 320 °C) to study the interaction of such IL with several metals and alloys employed in the construction of solar plants: Stainless Steel (AISI 304), Carbon steel (AISI 1018 and S275-J0). Electrochemistry Gravimetric method SEM+EDX Room temperature electrochemistry results. Potentiodynamic curves: both AISI 1018 and S275-J0 show tendency to pitting corrosion OCV curves: a quite stable corrosion potential is reached after 30000-40000 s Tafel plots and Rpol measurements: Low values of corrosion current densities, valuated with Tafel extrapolation and Resistance polarization method, result for all the alloys investigated (<2 A/cm2) with AISI 304 the most performing material. AISI 1018 Icorr (An) (A/cm2) Icorr (Cat) Rpol () βa (mV/dec) βc Icorr Rpol 1,74 0, 360 27740 133 484 1,63 0,555 0,234 63500 128 450 0,681 1,35 0,124 35900 121 554 1,20 AISI 304 Icorr (An) (A/cm2) Icorr (Cat) Rpol () β a (mV/dec) βc Icorr Rpol 0,022 0,011 1330000 131 257 0,028 1620000 146 310 0,026 0,0076 0,021 2360000 154 273 0,018 S275-J0 Icorr (An) (A/cm2) Icorr (Cat) Rpol () β a (mV/dec) βc I corr Rpol 0,0230 0, 201 970000 169 626 0,060 0,0240 0,206 735000 204 420 0,081 0,0590 0,186 663300 313 660 0,139 SEM and EDX analysis After the 10 days treatment, the IL solution remains yellow-clear and localized corrosion phenomena are detected on both the alloys surfaces. Comparison of the qualitatively trend of wt% of F and S ,deriving from IL anion, detected by EDX analysis on the specimen surfaces of AISI 304 (*) and AISI 1018 (°) after the immersion in EdMPNTf2N for 48 h and 10 days at 220°C. This behaviour denotes a no pronounced tendency to decomposition also after 10 days respect to imidazolium based ILs. AISI 304 AISI 1018 The nine points analyzed derive from 3 sites for each sample (3 disks of AISI 1018 and 3 disks for AISI 304, individually immersed in distinct beakers). SEM image showing localized corrosion on AISI 1018 and AISI 304 after 10 days immersion test at 220°C. ICP-OES analysis Alloys Cr (mg/KgIL) Fe Mn Ni AISI 304 22,86 71,19 - 23,02 70,83 188,8 56,00 70,49 285,0 11,22 AISI 1018 272,5 4,377 364,2 6,72 146,1 4,490 AISI 1018: wt% 0.14–0.20 C, 0.60–0.90 Mn, 0.035 P, 0.040 S, Fe balance density 7.87 g/cm3 AISI 304: Cr 17-20%, Mn < 2%, Ni 8-11%, C < 800, Fe balance density 7.93 g/cm3 After 10 days of immersion in the IL at 220 °C no negligible amounts of metals in solution is detected for both the alloys. Conclusion If EdMPNTf2N has to be used as fluid for high temperature applications in room atmosphere the surface of the containing vessels will have to be protected against corrosion.