Technical Note: On the So-Called Linear Polarization Method for Measurement of Corrosion Rates

A metal corroding in contact with a solution containing oxidizing agents (for example, O₂, H⁺, H₂O) acquires a potential—the corrosion potential Φ_k—which is a mixed potential representing a compromise between the potential Φ_r1, which the metal would display in the absence of the oxidizing agent, and the potential Φ_r2, which the oxidizing agent would engender on an inert metal. Under these conditions, the current,⁽¹⁾ i_k, representing the corrosion rate of the metal, is exactly balanced by an equal current representing the reduction rate of the oxidizing agent. Whereas no net current flows at the corrosion potential, a current flow can be measured if the metal is polarized slightly either anodic or cathodic to Φ_k. In this way, a plot of current i versus potential Φ may be constructed which crosses the potential axis...