Delamination of Poylmer Coatings from Metal Substrates: Submicroscopic and Molecular Aspects

Abstract

Delamination of organic coatings from metal surfaces can occur in a number of different ways, e.g. as pure cathodic delamination, as Filiform corrosion or a mixture of these. In fact, in most technical systems the pure cases are the exception and, of course, delamination is usually very slow. It has been shown that in fast delaminating systems the length scales may range between several 100 μm and several millimetres, while in systems which show slow delamination the reaction zones can be confined to submicroscopic distances [1]. This underlines the importance of investigation methods with submicroscopic resolution. As a very promising new technique Scanning Kelvin Probe Force Microscopy (SKPFM) was applied for the investigation of cathodic delamination and filiform corrosion on a submicroscopic scale [1, 2]. Indeed, these first investigations have shown that SKPFM gives basically the same information as the standard Scanning Kelvin Probe (SKP), but with a much improved resolution. It could be shown, for instance, that the extension of the reaction zone seems to be much narrower than would have to be assumed from the SKP measurements. Based on the knowledge about the different delamination types that was obtained from investigations with the standard SKP [3–12] the SKPFM should be the ideal tool to get information on the submicroscopic scale. However, SKPFM alone is not sufficient for revealing the underlying fundamental mechanisms; of even higher importance is the knowledge of the molecular and mesoscopic structure at the buried interface. In this paper a design for suitable model samples is proposed and first results are presented.