Abstract
A scanning electrochemical microscope (SECM) was used to evaluate heterogeneity of passive films formed on iron in deaerated pH 8.4 borate solution. The probe current image and specimen current image for the specimen electrode, which consists of two iron plates embedded into epoxy resin, were measured with a tip-generation/substrate-collection (TG/SC) mode in deaerated pH 8.4 borate solution containing [Fe(CN)6]4- as a mediator. The distinctions between epoxy resin and each iron plate were more clear in the probe current image than in the specimen current image. Moreover, the difference in thickness of passive film between two iron plates was distinguishable in the probe current image. The lateral resolution of the probe current image was about 40μm which was two times as much as the diameter (20μm) of the probe electrode.
