Conducting Polymers and Corrosion PPy—PPy-PDAN Composite Films Electrosynthesis and Characterization

We describe the electrosynthesis of a composite film consisting of polypyrrole and poly(1,5-diaminonaphthalene) (PPy-PDAN) on iron in neutral aqueous medium. The film structure was characterized by Raman and Fourier transform infrared spectroscopies. The composite film is composed first of layers of PDAN at the metal/film interface onto which PPy film is deposited. The first PDAN layers increase the film adhesion compared to PPy films alone. In addition, the composite redox potential is more anodic than that of PPy. The protective properties of PPy-PDAN composite were measured by plotting the open-circuit potential (E oc ) vs. time. Iron can be maintained in the passivation region for two days by PPy films while the duration with the composite films lasts up to two months. This latter result can be explained by a more anodic redox potential and a better adhesion of the composite film. In situ Raman spectroscopic analysis is used to characterize the film before and after the passivity breakdown.