This research takes a new approach to understanding the changes occurring in solution chemistry during localized corrosion. Ion chromatography is employed to probe the progression of solution chemistry within occluded cells. Ion chromatography is capable of detecting nanogram quantities of a wide variety of ions in solution volumes as low as 10 microliters. This technique permits the analysis of changes in solution chemistry at localized corrosion sites such as in crevices. New insights can be obtained into the fundamental processes that control corrosion pit formation and propagation. Surface analysis techniques (Auger spectroscopy and X-ray photoelectron spectroscopy) are used to examine the composition of passive films and surface corrosion layers that form before and after the onset of corrosion. %%% Localized corrosion of metals and alloys in aqueous environments is an especially damaging form of environmental attack. It has generally been accepted that the cause of the initiation and propagation of a localized corrosion site is the formation of a highly aggressive environment in an occluded cell that comprises the area of attack. Understanding obtained from the approach described in this study could have a significant impact on the development of strategies for mitigating pitting and crevice corrosion.