The Mechanism Research On The Anti-corrosion Of Conducting Polymers For Metals

Metal corrosion causes great economic loss and damage to industry and society. With the progress of industry and technology, it is important to research new materials of anti-corrosion. Coating technique for anti-corrosion holds the important position in the metal protection project, and they are playing the more and more vital role in the national economy construction. Due to the limit of its properties and technology, the anti-corrosion property of the conventional coating to metal is not very ideal. And lots of the coatings contain poisonous matters that may pollute the environment. So the exploration of green coating becomes one of the targets of the corrosion protection field. Since in 1985, Deberry reported firstly that conducting polymer can offer corrosion protection, conducting polymer has been extensively researched on corrosion protection, and now some paint coating containing conducting polymers have been developed. Although many researchers found that conducting polymers can reduce the corrosion rate of metal, but some researchers have different views. Because of the conductive polymer preparation, doping, research methods, as well as the different corrosive media, the results are inconsistent. Yet the mechanistic of corrosion protection of conducting polymers has not been reported exactly.Polyaniliane and polypyrrole are selected for their usage in this paper. Firstly research is carried out that whether conductive polymer's redox potential impact the anti-corrosion. In this paper, polyaniline and polypyrrole are synthesized on the 304 stainless steel matrix by cyclic voltammetry under the same scope of potential, and polypyrrole coatings are relatively compact. The corrosion behaviours of the coatings have been determined by electrochemical corrosion testing methods in 3.5 wt% NaCl solution for for various immersion times. Studies have shown that they have anti-corrosion on 304 SS, and polyaniline coating was found to be more effective than polypyrrole coating. As redox potential of polyaniline is higher than polypyrrole, and oxy-potential of conducting polymers will play an important role on the protection corrosion.Secondly, because of polyaniline has a special doped mechanism, redox properties, how does the different redox state of polyaniline protect metal by anti-corrosion? Polyaniline coatings are synthesized on the 304 stainless steel matrix by constant voltammetry under different potential, and with the increase of potential, polyaniline films become more loose and have different redox structures. The corrosion behaviours of the coatings have been determined by electrochemical corrosion testing methods in 3.5 wt% NaCl solution for various immersion times. Studies have shown that the corrosion potential are moving corrosion potential and orrosion current decline, so they have anti-corrosion on 304 SS. But with the increase of potential, anti-corrosion of polyaniline films are declining.Finally, as polypyrrole has advantages of environmental stability, no poison, Polypyrrole coatings are synthesized on the 304 stainless steel matrix by constant voltammetry under different potential, and with the increase of potential, polypyrrole films become more loose and have different redox structure. The corrosion behaviours of the coatings on 304 SS have been determined by electrochemical corrosion testing methods in 3.5 wt% NaCl solution for for various immersion times. Studies have shown that the corrosion potential are moving corrosion potential and corrosion current decline, so they have anti-corrosion on 304 SS. With the increase of potential, anti-corrosion of polypyrrole films are declining.