STP1056: Comparison of Current Interruption and Electrochemical Impedance Techniques in the Determination of Corrosion Rates of Steel in Concrete

    Berke, NS
    Senior research engineer associate, senior technician specialist, and marketing specialist, W. R. Grace & Co., Cambridge, MA

    Shen, DF
    Senior research engineer associate, senior technician specialist, and marketing specialist, W. R. Grace & Co., Cambridge, MA

    Sundberg, KM
    Senior research engineer associate, senior technician specialist, and marketing specialist, W. R. Grace & Co., Cambridge, MA

    Pages: 11    Published: Jan 1990


    Abstract

    Steel reinforced concrete is a widely used construction material. It is often the material of choice in bridges, parking garages, and marine structures because of its good durability and resistance to corrosion. However, over time, even well designed concrete is susceptible to chloride intrusion from deicing or marine salts or both, resulting in corrosion of embedded steel.

    By the time corrosion of steel in concrete is readily noticeable, major repairs are often required. A nondestructive means of determining the corrosion rate of inaccessible steel is thus needed. Electrochemical techniques such as polarization resistance are useful, however resistivities of concrete range from 1000 to greater than 30 000 ohm-cm. Furthermore, reference electrodes are usually greater than 25 mm from the working electrode (rebars). Thus, large ohmic electrolyte resistance is present, even at the low current densities associated with steel in concrete, and must be accounted for to accurately measure corrosion rates.

    In this paper we compare the use of current interruption correction for ohmic resistance to an electrochemical impedance measurement at 20 KHz. In general, we find a good correlation between the two techniques, and demonstrate that substantial ohmic resistances are present.

    Keywords:

    concrete resistivity, current interruption, electrochemical impedance, polarization resistance, reinforcing steel, ohmic electrolyte resistance, ohmic electrolyte compensation


    Paper ID: STP25289S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP25289S


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