The use of electrochemical impedance spectroscopy with segmented electrodes to study inhibition at the cut-edge of coil-coated systems

The use of multiple metal segmented electrodes has been applied to study the inhibition mechanisms for several anti-corrosion pigments that are commonly used in organic coatings. The relatively novel experimental methodology involves, firstly, polarisation of the coupled metal system at the common coupled potential but with the currents on the separated electrodes recorded individually and, secondly, the application of electrochemical impedance spectroscopy at the same coupled potential. For example, at the cut-edge of a coil-coated galvanised steel sheet, electrochemical data may be gathered simultaneously at an anodic potential for the zinc and at a cathodic potential for the steel substrate. Using this methodology the inhibitive efficiency for strontium chromate, calcium ion-exchanged silica and zinc molyphosphate inhibitors were determined under the electrochemical condition expected in service.