ELECTROREFLECTANCE SPECTRA OF PASSIVE IRON

The effects of frequency-modulation on the intensity and form of the i ron electroreflectance (ER) spectra in basic solutions over the potent ial ranges of passivity and oxygen evolution cannot be interpreted by the available models for ER of passive metals. A mechanism of the pass ive iron ER was proposed, allowing for electromodulation of optical po larizability of the layer of adsorbed water that forms surface charge- transfer complexes with the energy-nonuniform surface of the passivati ng film. The comparison of calculated and experimental ER spectra show s that changes in dipole component of the potential drop in the adsorb ed water layer due to changes of electrode potential contributed signi ficantly to sustaining the passive state of iron.