XPS STUDY OF PASSIVE FILMS FORMED ON AN IRON-ALUMINUM INTERMETALLIC COMPOUND IN ACID-SOLUTION

Surface films grown on the intermetallic B2-FeAl alloy after wet-mechanical polishing and after a wide range of anodic polarization conditions in 1N H2SO4 have been analysed by x-ray photoelectron spectroscopy. The results clearly indicate a remarkable enrichment of aluminium within all the films regardless of the growth conditions. Analysis of the metal-oxygen bonds has made it possible to distinguish several oxidized species. It has been found that most of the iron hydroxides are concentrated on the film surfaces, whereas aluminium hydroxides appear more homogeneously distributed over the depth of the oxide films. The thickness of the film shows an abrupt increase at 1 V, accompanied by a marked increment of Al hydroxide species.