  X-ray photoelectron spectroscopy combined with Ar+ ion etching is a powerful
concept to identify different chemical states of compounds in depth profiles,
important for obtaining information underneath surfaces or at layer interfaces.
The possibility of occurring sputter damage is known but insufficiently
investigated for corrosion products of Zn-based steel coatings like ZnCr.
Hence, in this work reference materials are studied according to stability
against ion sputtering. Indeed some investigated compounds reveal a very
unstable chemical nature. On the basis of these findings the reliability of
depth profiles of real samples can be rated to avoid misinterpretations of
observed chemical species.
