Corrosion reactions which take place during delamination in the vicinity of defects have not been understood up to now. In this paper the delamination of a simple model coating from clean steel and the delamination of technical coatings from petreated steel substrates are analysed with a scanning Kelvin probe. It is possible, with this technique, to follow the delamination in situ and to understand the basic corrosion mechanism at the metal/polymer interface.