Intelligent Corrosion Protection by Conducting Polymers

Use of intrinsically conducting polymer (ICP) coatings for corrosion protection has been discussed controversially for years. Quite a number of possible protection mechanisms are proposed, of which the possible passivation of the metal through the high potential of redox ICPs such as polypyrrole or polyaniline is maybe the most frequently stated. In this presentation the focus will be on the dynamic response mechanisms that such redox ICPs will show when a delamination front approaches them. Of special interest is the possibility of intelligent self-healing by conducting polymers that show a true electrochemically driven on-demand release of inhibitor anions. The trigger for the release is the potential decrease that occurs during delamination at the polymer/metal interface. It will be shown that the efficacy of conducting polymers for corrosion protection very much depends on how they are applied and on the conditions of the corrosion experiment, i.e. depending on the exact conditions a conducting polymer may have excellent protection capability or may lead to a disastrously enhanced corrosive attack. This paper will discuss how to counteract the negative properties of the conducting polymer, so as to truly benefit from the positive ones.