Abstract
Low energy ion‐scattering spectrometry has been used to obtain the composition‐depth profiles of air‐formed oxide films on a series of iron‐chromium alloys. By using iron, chromium, 
, 
, and 
as standards, the atom composition ratios Cr/Fe and 
have been obtained quantitatively as a function of sputtering time. The air/oxide interface appears to be oxygen‐rich or metal‐deficient. The Cr/Fe ratio is low at this interface but increases and peaks a few angstroms inside it. This ratio then diminishes continuously to its value in the alloy at the oxide/metal interface. The 
ratio diminishes continuously from the air/oxide to the oxide/metal interface and appears to be independent of alloy composition. There is no region of constant concentration of any of the components. The average Cr content of the oxide varies linearly with alloy composition but exceeds the Cr content of the alloy. This may be associated with the method of surface preparation. Based on differences in the shape of the composition profiles, it is speculated that the distribution and bonding of cations in the oxide phase, not their concentration, differentiate the stainless from the nonstainless alloys.