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Electrolysis in water wood stove, and how to prevent

 

We have a marine aluminium wood stove for our hot tub and it is developing electrolysis on the outside of the stove. We do have a pump and filter taking care of the tub and believe that may be the cause of the problem. By hanging a piece of zinc in the tub near the stove, do you think that will help. We have also run a copper wire and a copper bar directly from the pump to the ground. Is this the corrective action we should take? We never had this problem before and have had the tub for 16 years. Recently we had to replace the pump to the filter and feel it is the cause. Please advise.

Joan Stoermer
- Quincy, California, USA

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Electrolysis, or galvanic action, is the creation of a battery by connecting dissimilar metals with both an ionic path (the liquid) and a metallic path (the piping system). The way to stop the electrolysis is either to make everything out of one metal (impractical), or to eliminate the liquid path (impractical), or to eliminate the metal-to-metal path. My suspicion is that, in replacing the pump, some insulator was left out between the two metals--perhaps a piece of hose, a plastic bushing or coupler, or a dielectric union. You have to get it back in there.

Zinc would probably do little good in such a position anyway, but zinc cannot protect aluminum in unsalted water. Grounding the pump may be good for electrical safety but it can't stop the electrolysis action.

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