Semiconducting properties of surface oxide films
The Kelvin probe technique directly provides information about the work function of the surface oxide, which can be interpreted also as electrode potential, providing useful information about reactivity of surfaces and interfaces. An important topic in this context are novel Zinc-Aluminium-Magnesium alloys (ZAMs) where in earlier works the native oxide layer was shown to play a crucial role in the delamination behaviour (see e.g. ).
An important finding was that at the cut edge or at defects down to the steel, the beneficial effect of magnesium at least at the initial stages of exposure is mainly due to enhancing the effect of the zinc cations, which were found to replace reactive Fe2+ sites in the iron oxide layer and thus significantly decrease the oxygen reduction rate .
Further it was investigated how different pretreatments, such as alkaline and acidic cleaning, change the semiconducting properties of alumina as well as ionic mobility. A strong correlation between OH fraction and Fermi level position in the oxide was found [3-6].