EFFECT OF ZETA POTENTIAL ON ADHESION OF ORGANIC COATINGS

The force of adhesion of an aqueous phase (pH 9.6 borate) to steel in the presence of a xylene solution of hydroxy-terminated polybutadiene increases below the potential of zero charge (-550 mV vs Ag/AgCl). Incorporation of a high molecular weight quaternary ammonium cation in the xylene phase inhibits displacement of the organic phase at cathodic potentials. These results suggest that cathodic polarization of steel below the potential of zero charge can initiate cathodic disbonding. The disbonding will then irreversibly propagate by the alkaline attack of the cathodic electrolysis product on the organic film.