Potentiodynamic Polarization Testing of Zinc Anodes in Natural Waters

Project ID: 8623
Principal Investigator: Roger Turcotte
Research Topic: Repair and Maintenance
Funded Fiscal Years: 2015
Keywords: cathodic protection, galvanic anodes, sacrificial anode cathodic protection

Research Question

Will zinc anodes, boldly exposed to natural waters within the areas of Reclamation's responsibility, remain active or will they passivate and loose protective capabilities?

Need and Benefit

Zinc anodes when used in natural waters are not surrounded by activating, sulfate rich backfill material but must be boldly exposed. In some waters, this can lead to their forming a passive film and loosing protective capabilities. As a result Reclamation tends to avoid the concern by using magnesium anodes, which seem less likely to passivate. However, zinc anodes are considerably more efficient than magnesium (90% vs. 50% is typical)
and are not likely to cause coating damage if directly mounted to a coated structure. Potentiodynamic polarization testing could help to verify which waters might be a problem and which would not; this could provide
considerable benefit when Reclamation needs to cathodically protect structures.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

Potentiodynamic Polarization Testing of Zinc Anodes in Natural Waters (final, PDF, 2.7MB)
By Roger Turcotte / Daryle Little
Publication completed on September 30, 2015

Anodic potentiodynamic polarization is a common electrochemical research technique used to study the active and passive behavior of a metal in a particular environment. This technique forces the electrochemical potential of the metal across a range of potentials, while measuring the current density associated with a given potential. Passivating metals demonstrate a characteristic potentiodynamic polarization curve; the current required to shift the potential anodically beyond some point does not increase and often decreases. The current associated with metal in the passive range is characteristically small, indicating a very low level of metal corrosion. In this study, potentiodynamic polarization was attempted and, in fact, showed passivation of zinc in some artificial laboratory solutions.


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Last Updated: 4/4/17