We describe the electrochemical behaviour of sputtered IrOx films (SIROF) in dry propylene carbonate and the effects of addition of water to the solvent. Cyclic voltammetry and in situ optical absorption measurements show that only the Ir-III/Ir-IV redox system has to be considered in the various solvents used in this study. Finally, a new insight comes from measurements of laser beam deflections into the nature of mass transfers through the film interface.