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Residential Marine Seawall -- Corrosion of Metallic Components




I have carbon steel tie-back rods going between the concrete anchors in the yard and the stainless steel (T304)horizontal whaler that restrains the PVC sheet piling of the bulkhead. This is a marine application. The stainless steel whaler is submerged as is the ends of the tie-backs. I attached an aluminum block to the stainless steel whaler to serve as a self-sacrificing anode - thereby protecting the carbon steel rods. The aluminum is corroding AND the steel rods are also corroding. There are a LOT of people with marine water front homes that have similar problems. Any thoughts? Would this be an application for a impressed voltage system? Zinc Anode? This is a problem facing a jillion water front homeowners and home owner associations. People have tried stainless steel tie backs, plastic covered steel tie backs, wooden whalers, plastic coated wooden whalers. They all fail eventually and a very expensive job ensues in which a lot of very valuable landscaping is destroyed or compromised. I am a PE, but not in this field.

Robert Elmer Running
marine seawall construction - Wrightsville Beach, North Carolina
2006



Nothing is forever; you won't stop corrosion in its tracks, Robert. But it sounds like a problem if you have galvanized rods touching the stainless whalers. The galvanized coating will try to galvanically protect the whaler; when it is gone, the steel rod will try to galvanically protect the whaler. Since the rods are small in surface area compared to the whaler, they won't be able to do so for long.

It's not easy but I think the galvanized rods need to be properly insulated from the stainless whalers.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006


Try titanium-maybe expensive but best. Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia
2006



Sorry but I do not understand what you have described, but may be some advice anyway. Galvanic Series for metals Zn (as in galvanized) lowest, then Al, steel and finally 304 you mentioned. You are working with both the potential difference in these metals and the amount of exposed surface in your corrosion fight. As I understand it you are trying to protect the steel tie-back. Could this be painted with epoxy of powder coated? Could you exchange UHMW for one of the metal parts?
Regards, Jim

Jim Wood
- Concord, California
2006


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