Abstract
The basic operation of the Pearson bridge, a circuit for measurement of electrode potentials of remote electrodes in the presence of current flow, is described. Data on the effect of impressed current on the potential of steel electrodes in various systems containing corrosion inhibitors are presented. Certain oil-soluble inhibitors appear to form a film on the metal surface which causes a high rate of change of electrode potential with change in impressed current. The semi-quantitative relationship of this change, called for simplicity a film resistance, is demonstrated. Adsorption and desorption rates can be determined from this relationship. Inhibitors which adsorb rapidly invariably give nearly 100 percent protection in weight loss tests, whereas inhibitors which adsorb more slowly show a percent protection which is dependent on the relationship between adsorption time and duration of test. Water-soluble organic inhibitors do not exhibit this type of film, which may actually be dependent on the oil phase itself for its formation.
