The impact of non-uniformity and resistivity on the homogenised corrosion parameters of rebars in concrete – a circuit model analysis

ABSTRACT When rebar corrosion parameters are characterised from an electrochemical polarisation curve, the non-uniform rebar surface conditions need to be considered. In this research, a circuit model was developed to simulate the polarisation behaviour of rebar in concrete. It is found that the resistivity of concrete leads to non-uniform potential on the rebar, which causes the polarisation curve of the entire rebar to deviate from the Butler–Volmer kinetics. This, in turn, leads to an overestimation of the Tafel constants and the corrosion current density. Such deviations are more pronounced with higher concrete resistivity, especially when the active and passive rebar surfaces have a similar area ratio. The study recommends using potentiodynamic scans of representative reinforced concrete samples of the field conditions or the calculated parameters using an averaging technique, such as the proposed circuit model, to obtain accurate E-I curves or parameters for electrochemical modelling and corrosion rate prediction.