Application of the Kelvin Probe method for screening the interfacial reactivity of conducting polymer based coatings for corrosion protection

In our recent studies we could show that intrinsically conducting polymers definitely possess promising potential for application in intelligent corrosion protection coatings. One prerequisite for this was shown to be that macroscopic networks of the conducting polymers have to be avoided in the coating in order to avoid predominant and disastrously fast cation incorporation during the corrosion induced reduction of the polymer. Only then anions serving as inhibitors and safely stored in the conducting polymer will be efficiently released during a corrosive attack. This mechanism is more or less independent of the metal that has to be protected, i.e. it is a property of the composite coating derived from dispersing micro-clusters of conducting polymer in a non-conducting matrix and unspecific for the metal onto which it is to be applied. In this paper we focus on specific electrochemical reactions at the interface between the conducting polymer and the metal that were found to define further criteria for successful application. The aim should be that the conducting polymer is in electronic contact with the passive metal surface. However, the formation of an insulating interface, i.e. loss of electronic contact and hence functional inactivity of the conducting polymer, and enhanced corrosion are also possible. We will show how by application of the Kelvin Probe method a fast and easy screening between these three cases can be achieved.