Study of the carbon steel/alkyd coating interface with a scanning vibrating capacitor technique

Degradation of the carbon steel/alkyd coating interface is studied with a s canning vibrating capacitor technique. This method is shown to provide info rmation on the state of the metal under the coating, that is, the nature of the metal/polymer electrical double layer, as well as the diffusion rates for water, oxygen, and ionic forms of electrolyte to the steel/alkyd interf ace. Processes of the hydrolysis of adhesion bonds, metal corrosion, and th e polymer's cathodic delamination are investigated. The processes that limi t corrosion of the metal under the coating are discussed. It was found that the metal activation and corrosion are determined, for the steel/alkyd sys tem under study, by the oxygen diffusion flux through the polymer and by th e formation of differential aeration couples under the coating.