51314-4362-Contactless Kelvin Probe Electrode for Potential and Polarization Resistance Measurements of Reinforcing steel in concrete

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Product Number: 51314-4362-SG

ISBN: 4362 2014 CP

Author: Alberto Sagues

Publication Date: 2014

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The practical feasibility of using a Kelvin Probe as a novel reference electrode in the measurement of both potential and polarization resistance of reinforcing steel in concrete is demonstrated. The use of a Kelvin Probe in applications of this type offers a contactless means by which measurements with very high stability and modest sensitivity to working distance can be made. Unlike conventional wet-tip (e.g. Cu/CuSO4 (CSE) or saturated calomel (SCE)) reference electrodes which yield potential values that can drift more than 40 mV within three minutes of being placed on a dry sample surface the Kelvin Probe almost instantaneously provides values that drift less than +/- 1 mV over the course of the same time period. Multiple reinforced concrete beam test subjects with well-differentiated centrally corroding rebar segments were analyzed using both the Kelvin Probe and a SCE. The shapes of test subject potential profiles and the ranges of individual recorded values provided by use of the Kelvin Probe were found to be offset but comparable to those obtained independently by means of the SCE successfully identifying the corroding region of the rebar. The same beams were subjected to a small (i.e. 1-100 uA) galvanostatic polarizing current and potential variations in both the active and passive regions were recorded using the Kelvin Probe. The observed potential response and recovery curves were consistent in shape and magnitude with curves provided by conventional reference electrodes. The nominal polarization resistance was successfully obtained from the polarization data acquired with the Kelvin Probe. The Kelvin Probe’s use as a reference electrode shows promise to facilitate fast automated field corrosion data acquisition in cases where the use of a conventional wet-tip electrode would be disruptive or time consuming. Promising applications include facilitating assessment of corrosion condition of existing systems and related operations such as cathodic protection depolarization measurements.