Electrochemical transient techniques for the evaluation of reinforcement corrosion in concrete

A galvanostatic pulse technique has recently been developed which enables the transient electrochemical potential response of a corrosion interface to an applied current to be studied. The technique has shown some promise in determining the corrosion rate of steel in concrete in both the laboratory and in the field. However, this technique is less well known in the civil engineering community than other techniques and there are a number of pitfalls to be avoided in carrying outfield measurements. This paper reports on the results of a series of galvanostatic pulse transient response measurements carried out to determine the optimum measurement parameters for assessing corroding reinforcing steel in concrete. Measurements were conducted on bars, which were undergoing a range of corrosion rates, from passive steel to actively corroding steel. The duration of the applied galvanostatic pulse was varied from 5 s to 300 s and the sampling rate used to capture the transient response was also varied from 50 Hz to 10 kHz. The electrochemical potential transient response was analysed to obtain equivalent electronic components that comprise a series of capacitor and resistor pairs, whose values are dependent on the corrosion condition of the reinforcing steel. The corrosion rate was calculated from a summation of those separate resistive components, which could be identified as being associated with the corrosion interface. The selection of measurement parameters to give the most accurate assessment of corrosion rate of steel in concrete was discussed. Guidance is given on the use of the galvanostatic pulse transient technique to assess the corrosion rate of steel in concrete and for the interpretation of the data obtained.