Corrosion protection by organic coatings: electrochemical mechanism and novel methods of investigation

The application of electrochemical techniques for corrosion studies of organic coatings on reactive metals is considered from the analytical and mechanistic standpoint. Techniques such as electrochemical impedance spectroscopy (EIS), scanning vibrating electrode and scanning Kelvinprobe (SKP) an powerful tools to better understand the fundamental processes of corrosion at defects and underneath coatings. In the first part of this paper these three techniques are discussed in more detail as they present a very complementary approach to understand the ensemble of coating degradation, processes in defects and corrosion underneath coatings, respectively. The second part of this paper focuses on the two important mechanisms of cathodic delamination and filiform corrosion (FFC). Since both forms of corrosion are characterised by certain electrochemical reactions underneath coatings and are localised in nature, the discussion focuses on the application of the SKP to give new insights in these corrosion phenomena. (C) 2000 Elsevier Science Ltd. All lights reserved.