Linear Polarization Resistance Sensor Using the Structure as aWorking Electrode

A direct method of measuring corrosion on a structure using a micro-linear polarization resistance (mLPR) sensor is presented. The sensor includes three electrodes, where each electrode is fabricated on a flexible substrate to create a circuit consisting of gold-plated copper. The first two electrodes, or the counter and reference electrodes, are configured in an interdigitated fashion with a separation distance of 8mil. The flex cable contains a porous membrane between the pair of electrodes and the structure. A third electrode, or the working electrode makes electrical contact to the structure through a 1mil thick electrically conductive transfer tape placed between the electrode and structure. The reference and counter electrodes are electrically isolated from the working electrode and physically separated from the surface of the structure by 1mil. The flex cable can be attached to the structure through the use of adhesives or in the case of placement in a butt joint or lap joint configuration, by the joint itself. Corrosion is computed from known physical constants, by measuring the polarization resistance between the electrolytic solution and the structure. A controlled experiment using the ASTM G85 Annex 5 standard verifies the precision and accuracy of sensor measurements by comparing the estimated mass loss with witness coupons.