THE PROTECTION OF IRON AGAINST CORROSION WITH POLYMER-FILMS PREPARED BY CATHODIC POLYMERIZATION OF HALOGENATED XYLENES

Polymer films were prepared by cathodic polymerization of halogenated xylenes at an iron electrode in a non-aqueous electrolyte solution. The ability of the films to protect against corrosion was examined in an aerated 0.5 M Na2SO4 solution by polarization measurements of an iron rotating disk electrode uncoated and coated with the polymers. The best protection of the electrode was obtained with a polymer film prepared by cyclic sweeps of potential in an oxygen-saturated acetonitrile solution of α,α′-dibromo-p-xylene. Mechanisms of the corrosion protection were investigated on the basis of the Koutecky-Levich equation. Diffusion of oxygen in the aqueous bulk solution was not a rate-determining step in the corrosion process of the iron electrode coated with the polymer film. Rate constants of anodic and cathodic charge transfer reactions and diffusion coefficients of oxygen and ferrous ion through the film, obtained by computer simulation of the polarization curves, provide evidence for the protective mechanisms. © 1990.