Elucidation of corrosion phenomena with high lateral resolution using scanning probe techniques

• Applicants: Privatdozent Dr. Michael Rohwerder; Professor Dr. Wolfgang Schuhmann
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 33258059

Delamination at polymer/metal interfaces is a problem of widespread technological importance: The reasons for degradation of the interface can be manifold: mechanical stress, chemical degradation at the interface or electrochemically driven delamination starting at defects. The latter case is the most vicious one, as it can be extremely fast and often precedes other degradation reactions. A reliable prediction of long-term corrosion performance is not available yet, since the processes involved in the overall corrosion process - especially for degradation processes at buried interfaces - are not known in detail. To overcome this deficiency it is important to especially gain an in depth understanding of the electrochemical processes during delamination at high lateral resolution. Kelvin probe techniques, the most powerful tools so far for the investigation of delamination, provide only indirect information on electrochemical processes at the buried interface. Since even the high resolution achievable with scanning Kelvin probe force microscopy (SKPFM) will only provide sufficiently high resolution, if model coatings of just a few tens of nanometer thickness or even thinner are prepared. The project will hence focus on ultra thin model coatings. In order to obtain more detailed information about the electrochemical processes and the correlated interface degradation, for the first time a synergetic application of optical spectroscopy and different scanning probe techniques such as scanning electrochemical microscopy (SECM) and scanning Kelvin probe force microscopy (SKPFM) will be integrated and combined with specific imaging modi such as the O2 competition mode of SECM. This should allow for the first time direct investigation of the electrochemical behaviour at the buried interface. This approach will be first tested on simple corrosion problems such as corrosion at aluminium alloy surfaces with active inclusions and then it will be applied for delamination problems. The final aim is to establish a correlation between electrochemical activity at the buried interface and the corresponding delamination behaviour.

• DFG Programme: Research Grants