USE OF A SCANNING-KELVINPROBE IN THE INVESTIGATION OF ELECTROCHEMICAL REACTIONS AT THE METAL POLYMER INTERFACE

It is possible to measure the work-function of polymer coated materials with a Kelvin-probe. In a humid atmosphere this work-function is mainly given by the corrosion-potential of the metal substrate. The use of a scanning Kelvinprobe then allows to map the corrosion potential of polymer coated material with a local resolution of approx. 20-mu-m and to follow the delamination of polymer coatings as well in the vicinity of defects as on metal substrates, which are contaminated at the metal/polymer interface. Simultaneously, the diffusion of oxygen can be followed with a high local resolution after a jump of the oxygen activity within the gas phase. - The same techniques are used to analyse intrinsic defects within mono-molecular LB-films. In a dry gas phase the Volta potential map corresponds to the distribution of dipole-potentials and therefore allows to distinguish between covered and uncovered parts of the substrate, as the ordered LB-film shows rather large dipole-potentials. In a humid atmosphere the Volta potential map again is dominated by the corrosion potential of the substrate and therefore the delamination of the LB-film in the vicinity of defects can be studied as well as the stability of the film on the metal substrate far away from any defect.