Investigation of processes occurring at the metal/polymer coating/electrolyte interface

The methodical approach and the cell to study electrochemical processes occ urring during cathodic disbondment of a polymer coating are worked out. The y permit one to investigate the role of each process separately when superv ising the metal substrate potential, electrolyte and polymer coating compos ition at a metal/polymer/electrolyte interface. The cathodic disbondment of ethylene-vinyl acetate copolymer, polyisoprene and poly(vinyl chloride) co atings are studied. It is found that the cathodic disbondment rate for ethy lene-vinyl acetate copolymer coatings depends on double layer parameters at the interface. These parameters are determined by specific volume charge o f hydrated cations of the electrolyte, potential of the substrate, the pres ence of oxygen, surface active substances, etc. Based on the data of IR spe ctroscopy in internal reflection applied to disbonded films, it is establis hed that during the cathodic disbondment an electron transfer to polymer fu nctional groups, as well as an attacking of the adhesion bonds by active in termediates of oxygen reduction, occurs resulting in an electrochemical deg radation of the polymer and an adhesion loss. It is shown that the electroc hemical transformations at the steel/poly(vinyl chloride) interface can lea d to the appearance of new adhesion bonds, increasing adhesion strength and decelerating the cathodic disbondment.