This paper describes a new experiment for studying crevice corrosion. A wire beam electrode was employed in this experiment to measure electrochemical parameters directly from crevice area and these parameters were used to calculate instantaneous crevice corrosion kinetics. A clear correlation between calculated corrosion depth map and real corrosion appearance was obtained. Although crevice corrosion has been studied extensively and been modelled mathematically over the past decades, some aspects of crevice corrosion remain unclear and the completeness and accuracy of the proposed crevice corrosion mechanisms and models are often not experimentally verified. This situation may largely be due to technical difficulties associated with conventional crevice corrosion experiments.
Crevice corrosion is a heterogeneous electrochemical process in nature.
When crevice corrosion occurs, there is a distinct separation of the anodic and cathodic regions on the metal surface and different electrochemical reactions occur on the anodic and cathodic areas. Electrons continuously travel from the anode areas to the cathode areas through the electrode body and at the same time ions travel between anode and cathode areas through the electrolyte, resulting in rapid corrosion penetration on crevice areas. To characterise a crevice corrosion process, electrochemical parameters at local areas of a working electrode surface such as local anodic reaction current, have to be determined. However, conventional electrochemical techniques have major difficulties in doing this. This is mainly because conventional electrochemical techniques use a one-piece electrode, an electrode which is constructed by a single piece of metal or other electrically conductive material of a chosen size.