Electrochemical techniques for studying corrosion of reinforcing steel: Limitations and advantages

This paper presents a comparison of the results obtained by different electrochemical techniques when applied to passive and active steel embedded in mortar or in simulated pore water solutions. The techniques investigated include polarization resistance by means of current or potential steps, potentiodynamic tests at different polarization rates, the application of potentiostatic and galvanostatic pulses, and electrochemical impedance spectroscopy (EIS). The differences between the corrosion current density (i(corr)) values obtained using different techniques, or by applying the same technique in different conditions, are predicted by theory, and are often greater than an order of magnitude. Many of these errors, particularly in passive systems, are a result of incorrect application of the electrochemical techniques, rather than the techniques themselves being inadequate for probing the behavior of the steel/concrete system. When electrochemical techniques are used correctly, they can provide fast, quantitative, and trustworthy data, although not precisely exact, regarding the corrosion rate of steel in concrete.