The passivation and corrosion of polycrystalline iron have been investigated using combined ultrahigh vacuum/electrochemical methods (UHV-EC) in berate electrolytes with and without sulfate contamination under a variety of experimental conditions. The presence of sulfate ions leads to enhanced anodic dissolution of iron under all circumstances, along with an increased hydroxylation of the surface film. Fitting of the iron surface is also observed. We report an unexpected effect : exposure of the electrode surface to sulfate solution significantly retards subsequent passivation in berate solution. This inhibition is observed even if the sulfate exposed sample is cleaned to the atomic level in UHV, prior to immersion in berate. This retardation manifests itself by way of a systematic trend toward higher potentials for the active-passive transition and the observation of increased anodic currents in the passive region. We attribute this effect to changes in surface morphology brought about by pitting of iron in sulfate solutions.