The Physical Meaning of Electrode Potentials at Metal Surfaces and Polymer/Metal Interfaces: Consequences for Delamination

Abstract

A key parameter that controls the formation of a local galvanic element during the deadhesion of paint from base metals is the potential gradient between a defect in the paint and the intact metal oxide/polymer interface. The suitable development of zinc coatings allows for control of the potential at the intact interface and thus improvement of the delamination behavior. However, no systematic in-depth study on the origin and meaning of electrode potentials at polymer/metal interfaces or even bare metal surfaces has been presented yet, although in many recent publications Volta potential differences between inclusions and matrix measured on the surfaces of alloys are often interpreted as providing information on the galvanic activity during corrosion. It is the focus of this paper to present a detailed analysis of the origin of the potentials measured on the different materials and to point out what conclusion can be drawn from their values. Special focus is given to the technologically important system Zn–Mg.