The premature deterioration of concrete structures due to corrosion of the steel reinforcement is often a major problem in civil engineering. Polarization and electrochemical impedance spectroscopy can be used to study the development of passivity and corrosion mechanisms, and assess electrochemical kinetics on the steel reinforcement. However, in-situ corrosion rate measurements on reinforcing steel in laboratory test cubes, or structures on-site, are not always easy to obtain with either dc or ac techniques. This is because it is often virtually impossible to measure polarization resistance (Rp) at zero frequency or even measure the charge transfer resistance (Rct) due to the large diffusion components associated with the overall mechanisms.
This paper discusses the implementation of harmonic analysis as a corrosion rate measurement technique on laboratory concrete specimens prepared with and without the addition of sodium chloride to the mix. The analysis technique, which is an extension of electrochemical impedance, is rapid to use. Harmonic analysis also has the advantage over other electrochemical measurements in that it enables the corrosion rate to be determined by simultaneous determination of the corrosion current and evaluation of Tafel constants. The data showed that there was a good agreement between the corrosion rates and the corresponding corrosion potentials.