Potentiodynamic Purpose

The potentiodynamic technique is used to examine the overall corrosion behavior of a system. In a typical potentiodynamic scan, the potential of a metal specimen is slowly swept over a very wide range. During the sweep, the metal sample may undergo different electrochemical reactions, resulting in anodic and cathodic cell currents which may vary over many orders of magnitude. The graphical output of the experiment is a plot of log(current) versus potential. Analysis of the curve often can yield the following types of information:

• Corrosion potential.
• A rough estimate of corrosion current.
• Potential region for passivity.
• Mechanistic information.

ASTM Standard G5, “Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements,” contains useful information about potentiodynamic measurements.

NOTE: The above description describes the “classical corrosion” use for the potentiodynamic technique. You can also use the potentiodynamic technique as a general-purpose tool to obtain controlled-potential current-versus-potential curves. The curves can cover narrow potential ranges, be run quickly, or be used for purposes quite different than those described above.