Electrochemical measurements on concrete bridges for evaluation of reinforcement corrosion rates

The study was undertaken to obtain data for developing of a methodology and standard for instruments to evaluate the corrosion rate of steel in concrete structures. Measurements of the polarization resistance of reinforcing steel were made with three devices, two of which operated on the principle of linear polarization with or without signal confinement. The third was based on superimposed current pulses of high and low frequency with signal confinement. Bridges were chosen as representative of three environmental conditions: marine environments regions with mild winters and low use of deicing agents, and regions with cold winters and characterized by extensive use of deicing agents. Measurements procedures were described, and the data obtained were presented on plots of corrosion current (i_c) vs corrosion potential (E_c). Values for i_c were low almost independent of E_c when E_c was more noble than about -0.25 V (Cu/CuSO₄), currents increased as shifted in the negative direction. Values of i_c were inversely proportional to concrete resistance. The i_c results were discussed in terms of the resistance and moisture content of the concrete. The guard electrode confined signal distribution, with confinement dependent upon the resistivity of the concrete.