The influence of surface charge density on the fracture of zinc single crystal electrodes

Abstract

This study suggests that variation in the charge density on metal electrode surfaces may affect the plasticity and fracture of model metals such as zinc. It seems likely, moreover, that double layer phenomena may play a role in the environmental embrittlement of other metals and alloys as well. In this view, one might anticipate that phenomena such as stress corrosion cracking -- in which case electrical double layers are clearly present -- may be sensitive, in part, to the charge density on the metal surface. This may be especially true in the range of potentials for a particular system where film formation is unlikely -- i.e., cathodic potentials, for example, at which premature failure is usually attributed to hydrogen embrittlement. It should be appreciated that changes in the charge density on a metal surface may be induced by means other than by applied electrode potentials. If hydrogen behaves as an electropositive adsorbate at the surface of the metal, a change in the charge density will again occur by the transfer of charge from hydrogen to the metal surface atoms. Hence, the model shown in Fig. 3 may be relevant, for example, to the atomistics of hydrogen embrittlement as well as to liquid metal embrittlement.