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Potentiodynamic Polarization Testing to Confirm the Suitability of Zinc Anodes in Natural Waters Specific to Reclamation

Project ID: 6793
Principal Investigator: Roger Turcotte
Research Topic: Repair and Maintenance
Funded Fiscal Years: 2014
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

None

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.

Literature Review: Potentiodynamic Polarization Testing to Confirm the Suitability of Zinc Anodes in Natural Waters Specific to Reclamation (interim, PDF, 447KB)
By Roger Turcotte
Report completed on September 23, 2014

In some fresh waters, zinc anodes can lose their ability to protect an immersed structure. The interplay of the chemical components of a fresh water is complex, so that determining by chemical analysis when zinc anodes can be used and when they will passivate is not straight forward; and field testing to ascertain passivation can take months. It is thought that potentiodynamic polarization might provide quick and simple way to test for this behavior.

In this scoping study, the literature wa
Keywords: cathodic protection, galvanic anodes, sacrificial anode cathodic protection, zinc anodes

This information was last updated on October 22, 2014
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