Studies on Galvanic Couples: II. Some Potential-Current Relations in Galvanic Corrosion^*

A graphic method of expressing the electrical characteristics of a galvanic couple was developed by the application of Kirchoff’s laws to a couple consisting of separate electrodes, each with an ammeter in series. When an external emf was impressed between the couple and a third electrode, also with an' ammeter in series, a definite current pattern was established, depending on the relative directions and magnitudes of the impressed emf and the potential of the couple. These relations were demonstrated with the iron-magnetite couple. Under the conditions used, a discontinuity in the potential-current relation was observed, when the couple was cathodically polarized over a sufficient range of current. This discontinuity or “break” coincided with reduction of current, circulating within the couple, to zero.