Impedance based method for non-contact determination of the corrosion rate in buried metallic structures

The electrochemical impedance spectroscopy has been employed in the present investigation to assess the polarisation resistance of carbon steel rebars in different electrolytes. The measurements have been performed using the classical 3-electrode arrangement, where the element under test is the working electrode of the potentiostat, and a new 4-electrode arrangement where the element under test is floating from the electrical point of view (e.g. contact-less technique). The polarisation resistance values obtained using the contact-less technique are very close to those obtained using the traditional 3-electrode arrangement. The measurements, performed in a wide range of electrolyte resistivity values (including mortar) have thus demonstrated the applicability of this new technique for on-site corrosion rate assessment.