Measurement of corrosion rate of reinforcement has become an essential procedure in maintenance, repairing and service life prediction of RC structures. One of the most widely used methods in the field is the linear polarisation resistance (Rp) technique. With the aid of a "sensorised guard ring", this electrochemical technique has many advantages for its ability to estimate corrosion rate (Icorr). The principle for the estimation of corrosion rate is based on the confinement of the polarised surface of the reinforcement and on the Stern-Geary equation (Icorr = B/Rp). However, there are two problems in the application of this technique: (1) Theoretically, the polarised surface of steel rebar can not always be fully confined by the "sensorised guard ring"; and (2) The estimated value of parameter B, which is estimated to fall within the range of 26 mV to 52 mV, and which has widely been used in the determination of the corrosion rate, is actually not suitable for all the corrosion cases of RC structures. This paper theoretically analyses the errors arising from neglecting the implications of the problems mentioned above, and their possible misleading outcomes. (A)
Abstract