NUMERICAL SIMULATION OF CORROSION RATE DETERMINATION BY LINEAR POLARIZATION

摘要

The polarization resistance technique is an accepted method of quantifying the corrosion rate of reinforcing steel in concrete. However, in the literature some doubt has been expressed regarding the reliability of polarization resistance measurements when applied to structures significantly influenced by macrocell action. As experimental tests are mostly performed in a laboratory environment using small specimens, correlations to quantify the effects of macrocell versus microcell action have not been performed. In order to elucidate this possible problem, the polarization behaviour of a planparallel arrangement of a two-component active/passive macrocell was investigated by a numerical analysis. The electrochemical behaviour of the concrete electrolyte and the steel/concrete interface have been modelled by a network of discrete linear and nonlinear resistive elements, respectively. The numerical results obtained clearly demonstrate that the polarizing current is distributed over the two components. For the corroding component of the macrocell the corrosion rate was slightly underestimated by the polarization resistance measurement. However, the corrosion rate of the passive component was extremely overestimated. Based on the results of the numerical simulation it was concluded that passive steel is erroneously identified as actively corroding steel, both from potential as well as from polarization measurements.