Observations on the Behavior of Steel Corroding under Cathodic Control in Soils

Abstract

Observations and measurements were made on the behavior of steel corroding under cathodic control in a wide variety of soils. The criterion for cathodic control was the relatively slight change in the potential of the anode produced by increasing the current density, as compared with the potential change of the cathode. The more positive open‐circuit potentials assumed by the cathode with time indicated that the potential of the cathode tended to approach the potential of the oxygen electrode for the particular environment. Approximately linear correlations between the loss of weight of the anodes of the corrosion cell, the maximum short‐circuit current developed by the cell and the current at the corrosion potential suggested a possible electrical method for measuring the corrosiveness of soils. The development of corrosion products in soils was observed through glass in specially designed corrosion cells. The most characteristic development in the soils studied was the formation of a dense membrane of iron oxide between the anode and the cathode. A probable relation between membrane formation and rate of corrosion is suggested.