Erratic impedance measurements of steel in concrete were traced to variability in the contact configuration between the counter electrode (CE) and the surface of the concrete. A stable contact over a small portion of the concrete surface improved reproducibility. The relative placement of the CE, reference electrode (RE), and working electrode (WE) could be manipulated to select effective solution resistance over a wide range (4.66:1) of values. Results agreed with predictions from a numerical model of the primary current distribution of the system. Except for the offset in the real component, the electrochemical impedance response of the specimens essentially remained unchanged by controlled variations of the CE configuration. However, this may not be the case when the interfacial impedance is not distributed evenly over the surface of a WE.
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Pech‐Canul et al. (1998) studied this question.
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