An XPS characterization of FeCO3 films from CO2 corrosion

The objective of this study was to systematically characterize iron carbona te (FeCO3) using X-ray photoelectron spectroscopy (XPS) to aid in the ident ification of potentially passive films on specimens exposed to carbon dioxi de (CO2) corrosion. To achieve this, an FeCO3 precipitate was prepared in a chemical reactor under anaerobic conditions and Ostwald ripened for 48 hou rs at 75 degrees C. Its characteristic binding energies were determined, an d its decomposition and oxidation behavior were studied. The examination re vealed that FeCO3 is stable in the ripened form and does not alter its stru cture with extended exposure to dry air. In the unripened form, however, Fe CO3 is unstable and quickly decomposes into Fe2O3 in air. These results are applied to the XPS analysis of films on actual specimens exposed to CO2 co rrosion in an experimental flow loop. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.