ABSTRACT
References ............................................................................................................ 461
12.1 INTRODUCTION
When a corrosion process proceeds by an electrochemical mechanism, electrochem-
ical methods can be applied in addition to chemical, surface analytical, and other
methods. Electrochemical corrosion processes consist of anodic and cathodic partial
reactions that are coupled with an electronic current in the metal and an ionic current
in the electrolyte. The partial processes and with them the partial current densities are
uniformly distributed in time and location over the surface, forming a homogenous
mixed electrode resulting in uniform corrosion (1). In the case where the anodic and
cathodic partial current densities are spatially separated, anodic and cathodic regions
are formed. Such electrodes are designated heterogenous mixed electrodes. Many
localized corrosion phenomena such as, for example, pitting, crevice, galvanic,
erosion and stress corrosion cracking (SCC), and corrosion fatigue are the result of
the formation of heterogenous mixed electrodes.
