Technical Note: The Need for Caution in the Use of Cyclic Voltammetry for Predicting Iron Corrosion Behavior

The potentiodynamic scan technique has been extensively used as an accelerated electrochemical test to establish the active and passive characteristics of numerous metals and alloys in various environments.^1-5  The maximum anodic current in the active-potential region, called the critical current density, indicates the ease of passivation for the particular specimen-environment combination. In this way, a series of alloys (or environments) can be ranked according to their tendency to passivate and long-term performance characteristics can be predicted. There has been considerable discussion in the literature about the most appropriate scan rate to use for reliable ranking and predicting (slow vs intermediate vs fast)^6-8  and the fact that certain material corrosion properties, such as pitting potentials, are strongly influenced by the scanning rate used.⁹  Nevertheless, the potentiodynamic approach has been reasonably successful as a rapid, accelerated test of long-term corrosion susceptibility. In this note, results pertaining to iron passivation...