High energy-resolution x-ray photoemission spectroscopy (XPS) is used in conjunction with scanning probe microscopy to investigate the influence of calcium carbonate coatings on the adsorption of aqueous CrO@sub 4@@super 2-@ on epitaxial Fe@sub 3@O@sub 4@/MgO(001) surfaces prepared by oxygen plasma assisted molecular beam epitaxy (OPA-MBE). Deposition of calcium carbonate films was accomplished with the use of a polymer-induced liquid-precursor (PILP) process, which utilizes polyaspartate to suppress growth of crystal aggregates and results in the formation of flat films. Of the three polymorphs of CaCO@sub 3@, the films primarily consist of a combination of vaterite and calcite with undetectable amounts of aragonite. X-ray photoemission analysis and atomic force microscopy reveal a thin polymer interfacial layer between the underlying Fe@sub 3@O@sub 4@ and carbonate overlayer which acts as a template for vaterite growth. An increase of the intensity in the low binding energy shoulder of the Fe 2p@super 3/2@ core-level and a decrease in the Fe(III) non-charge transfer satellite is evidence of an increase in Fe(II) at the magnetite surface as a result of the aqueous growth environment. This result is consistent with surface reduction found during the interaction of Fe@sub 3@O@sub 4@/MgO(001) with liquid water. The effects of carbonate coating on substrate reactivity, emphasizing electron transfer reactions responsible for the reductive immobilization of Cr(VI)O@sub 4@@super 2-@ will be discussed. These results have application in chromate remediation efforts centered on the reduction of chromate contamination by Fe(II).