Scanning vibrating reference electrode technique: a calibration study to evaluate the optimum operating parameters for maximum signal detection of point source activity

Abstract

The application of scanning electrochemical techniques to evaluate and spatially resolve corrosion activity has progressively increased over the last 20 years. Electrochemical scanning techniques are based principally upon the assumption that localised corrosion, where the anodic and cathodic processes take place at separate sites, can be represented as point sources. The electric field generated by sites of localised corrosion consists of equipotential lines which can be measured and graphically represented as a contour map. Many modern day systems use either a static or vibrating reference or quasi-reference electrode, to measure the electric field, more specifically the field normal (perpendicular) to the surface. The latter of these systems, namely the vibrating electrode, allows for improved resolution and a lower minimum detectable signal. The following paper presented here discusses a study conducted to evaluate the influence of the operating parameters on the resolution and minimum detectable signal measurable using a scanning vibrating electrode system. Measurement of the electric field generated at a point source, namely, a gold point in space (PIS) electrode, is used to evaluate the effect of parameters such as probe scan speed, vibration amplitude and probe–sample distance on the peak output potential and the resolution, defined here as the ratio of the peak potential to the full width at half-maximum peak potential (FWHM).