Cyclic voltammetry, electrochemical impedance spectroscopy and surface enhanced infrared absorption (SEIRA) spectroscopy have been applied for the study of the electrical double layer of the magnetron sputtered thin film Pb|1-ethyl-3-methylimidazolium tetrafluoroborate room-temperature ionic liquid system. A wide potential range of ideal polarizability has been established for the system between −1.6 and −0.1V vs. Ag|AgCl in the same ionic liquid, in which the differential capacitance-potential curve is shown to have two maxima with a minimum at the perceived potential of zero charge. The first application of the in situ SEIRA technique for the study of Pb electrodes in an electrolyte solution is shown and the results are put into context of the latest developments concerning screening of metal interfaces in ionic liquid medium. Slow kinetics of oxide reduction reaction is demonstrated, which may limit the application of dry ionic liquids in lead-acid batteries.