An XPS study of passive film formation on Fe30Mn9Al alloy in sodium sulphate solution

The passive film formed on the surface of the Fe30Mn9Al alloy in 1 M sodium sulphate (Na2SO4) aqueous solution has been studied by X-ray photo-electron spectroscopy. The results of depth-concentration profiles analysis suggest that the passive film consists of bound water, hydroxyl species, Fe3+ hydroxide, oxides of Fe3+ and Fe2+, oxides of Mn4+ and Mn2+, Al3+ hydroxide and Al3+ oxide. The passive film is probably hydrous. It seems that there is a transition layer constituting of the low valent oxides and the metallic elements between the passive film and alloy matrix.