Electroactive, or 'conductive', polymers are a rapidly expanding area of research with proposed applications ranging from batteries or electronic circuitry to artificial muscles and actuators. An emerging application for these materials is as constituents of corrosion resistant coatings. An important factor in any corrosion resistant coating is the level of porosity it possesses. Minimisation of porosity may be highly desirable for the production of highly protective films. This work aims to study methods for controlling the porosity of polypyrrole films for their possible use as corrosion resistant coatings. It has been observed that surfactants can modify the structure and morphology of polypyrrole on inert substrates such as platinum or indium-tin oxide glass, and on the non-inert substrate mild steel. This has involved the study of the conditions necessary for polymer deposition on mild steel where the tendency for metal dissolution competes with the polymerisation reaction. Corrosion studies were carried out, firstly, to assess the corrosion potentials for such films and, secondly, via Tafel extrapolation to determine the effects of film thickness and anionic surfactant concentration on the corrosion rates obtained. Further corrosion studies were performed on polypyrrole films with additions of molybdate corrosion inhibitor species and anionic surfactants. It was found that polypyrrole with additions of anionic surfactants had little or no effect on the corrosion characteristics of mild steel in saline environments. However, in the presence of molybdate and certain levels of surfactants, excellent corrosion resistance characteristics were observed. It is proposed that the reduction of polypyrrole occurs at large negative corrosion potentials, resulting in the formation of an insulating polymer film that is incapable of acting as a site for displaced corrosion reactions around which many of the theories of electro active polymer corrosion protection have previously been based.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:271450 |
| Date | January 2002 |
| Creators | Breakspear, S. |
| Publisher | University of Portsmouth |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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