Polyaniline-related ion-barrier anticorrosion coatings: I. Ionic permeability of polyaniline, cationic, and bipolar films

Ionic permeabilities of coating films were studied with a variety of experimental methods including measurements of membrane potential, salt diffusion, and electron spectroscopy for chemical analysis (ESCA). The results show that polyaniline (PAn) allows diffusion of anions (if PAn is dispersed in a cationic polymer matrix, the resulting film may have cationic defects that allow the passage of cations), a cationic film is permeable to cations, and the combination of a PAn containing primer with the cationic topcoat is an ion-barrier which delays penetration of both anions and cations.