STP558: Electrochemical Technique for Determination of the Instantaneous Rate of Atmospheric Corrosion

    Kučera, V
    Senior research scientist and director of research, Swedish Corrosion Institute, Stockholm, Sweden

    Mattsson, E
    Senior research scientist and director of research, Swedish Corrosion Institute, Stockholm, Sweden

    Pages: 22    Published: Jan 1974


    Abstract

    The aim of this investigation was to develop a technique and equipment for the measurement of the instantaneous rate of atmospheric corrosion of metals. An electrochemical method was chosen for this purpose and a technique was developed for continuous measurement and recording of the currents generated in models of the electrochemical corrosion cells which occur on the metal surface when exposed to the atmosphere. Two types of cells were used, galvanic cells consisting of steel and copper electrodes and electrolytic cells consisting of only one type of electrode, namely, steel, zinc or copper. In the latter type of cell an external emf was applied. The cell current was found to vary between 10-10 and 10-3 A in accordance with changes in climatic conditions, the changes being at least in qualitative agreement with changes in the rate of atmospheric corrosion as earlier reported in the literature. An inexpensive electronic integrator was developed for estimation of the accumulated quantity of cell current over a certain period of time. This device integrates separately on two counters the amount of current during periods with low current and during periods with high current. A time counter also records the exposure time during which the current exceeds a chosen value. This time counter can be used to measure the time of surface wetness, that is, that part of the period of exposure when the corrosion current is of practical importance. Efforts are now being made to find the quantitative relation between the cell current and the atmospheric corrosion rate. It is believed that the technique will prove to be a useful tool for the investigation of atmospheric corrosion in the laboratory as well as on test sites out of doors and in industrial applications.

    Keywords:

    atmospheric corrosion testing, electrochemical measurements, corrosivity of atmosphere, time of panel wetness, relative humidity, sulfur dioxide, carbon steel, copper, zinc


    Paper ID: STP32166S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP32166S


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