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-mecha nical polishing and after a wide range of anodic polarization conditio ns in 1N H2SO4 have been analysed by x-ray photoelectron spectroscopy. The results clearly indicate a remarkable enrichment of aluminium wit hin all the films regardless of the growth conditions. Analysis of the metal-oxygen bonds has made it possible to distinguish several oxidiz ed species. It has been found that most of the iron hydroxides are con centrated on the film surfaces, whereas aluminium hydroxides appear mo re homogeneously distributed over the depth of the oxide films. The th ickness of the film shows an abrupt increase at 1 V, accompanied by a marked increment of Al hydroxide species.