EFFECTIVENESS OF POTENTIAL MEASUREMENTS FOR ESTIMATING CORROSION OF STEEL IN CONCRETE. CORROSION OF REINFORCEMENT IN CONCRETE. PAPERS PRESENTED AT THE THIRD INTERNATIONAL SYMPOSIUM ON "CORROSION OF REINFORCEMENT IN CONCRETE CONSTRUCTION", BELFRY HOTEL, WISHAW, WARWICKSHIRE, MAY 21-24, 1990

In the United States, potential mapping of steel reinforced concrete bridge decks is a common technique for estimating corrosion damage to a structure. Measurements in the laboratory show that open circuit potential is a good indicator of the corrosion rate of steel in concrete, but similar measurements on bridge decks reveal no such relationship between potential and corrosion rate. A small, portable computer system was developed and used to measure the open circuit potential and corrosion current of steel in concrete. The system is designed to control and monitor the potential of the steel by modulating the applied current. The technique of current interruption is used to eliminate iR error during polarization resistance measurements. In the laboratory, the results reveal that under conditions of low corrosion, the potential of steel, vs SCE, can vary from -0.3 to -0.2 V, and the potential of an actively corroding steel can range from -0.6 to -0.4 V. Preliminary measurements in the field, repeated over several weeks on three bridge decks, indicate that this inverse relationship of potential versus corrosion does not exist. The results of this study and sources of error in these measurements are discussed.(A) For the covering abstract of the conference see IRRD 831449.