Electrochemical studies of iron and oxides of iron

Aspects of the electrochemistry of iron and its oxides have been reviewed, emphasis has been placed on discussion of the factors relevant to the dissolution processes. The preparation of electrodes of magnetite (Fe3O4) with suitable characteristics for electrochemical studies is described. The responses of stationary electrodes to potentiostatic, potentiodynamic and alternating currents have been investigated. The results can be interpreted in terms of solid phase reactions at the electrode at short times. Subsequently nucleation and growth processes have been identified at negative overpotentials. Dissolution processes giving rise to cathodic currents are investigated at positive overpotentials. The role of the flux of dissolution products from the electrode on dissolution rate is also discussed. The semi conducting nature of iron oxides is shown to have a profound effect on the electrochemistry of these materials. Parallels are drawn between the semiconducting properties of the crystals and their electrochemical response. The dissolution of magnetite under potentiostatic control has been studied. Faradaic processes are followed coulometrically and the overall removal of iron species (crystal dissolution) followed analytically using atomic absorption spectroscopy. The results have indicated a variation in current efficiency of the dissolution process with applied potential.