Surface Analysis of the Iron Wire Undergoing the Corrosion on Contacting with Frozen Aqueous Salt Solutions

In this study, we investigated the surface properties of iron subjected to corrosion in contact with frozen salt solutions, focusing on the effects of solution aeration and salt type on ferrous iron dissolution behavior. X-ray photoelectron spectroscopy (XPS) was used to examine the surface conditions after corrosion. Image analysis of the frozen media indicated that dissolved oxygen in freeze-concentrated solutions (FCS) plays a crucial role in the dissolution process. XPS analysis confirmed the formation of iron hydroxide and iron oxyhydroxide on the iron surface, suggesting a reaction mechanism similar to that observed under atmospheric conditions. Additionally, surface analysis revealed that specific salt ions—such as F−, Cl−, and Cs+—exhibit a tendency to adsorb onto the iron surface under conditions of pronounced dissolution. These hard anions form complexes with Fe (II) ions, thereby promoting their dissolution. Moreover, Cs+ ions readily adsorb onto FeOOH, creating a concentration gradient near and beyond the iron surface that further promotes iron dissolution.