INSTANTANEOUS CORROSION RATE MEASUREMENT WITH SMALL-AMPLITUDE POTENTIAL INTERMODULATION TECHNIQUES

With the intermodulation technique, a potential distortion using two s ine waves is applied to a corrosion system. The alternating current (A C) response consists of amplitudes measured at different frequencies. Simple relations are derived from the current-vs-potential relation fo r a corroding process under activation control, from which the corrosi on rate and Tafel parameters can be calculated. These are valid when t he amplitude of the applied potential distortion is sufficiently small . With the intermodulation technique, the corrosion rate and Tafel par ameters can be obtained within one measurement, which makes this techn ique an ideal candidate for application as a corrosion monitoring tool . Results obtained with this technique were shown to be in agreement w ith other electrochemical methods for corrosion rate measurement, such as Tafel extrapolation, linear polarization resistance (LPR), and ele ctrochemical impedance spectroscopy (EIS).