Heat exchanger zinc

[jhwelch]

I have a heat exchanger custom made by Sendure. When it was being
designed I was asked if I wanted a fitting for a zinc. My old heat exchanger
had one so I had them put one in.

Now I'm wondering just how important that zinc is. It's in the salt water
flow and gets eroded somewhat quickly. The heat exchanger is
mounted on a bulkhead, so the only "electrical" connections to anything
are the fresh and salt water lines.

Should I keep replacing this pencil zinc or not worry about it?

-jonathan

[Kelly]

Hello Jonathan,

While not an expert, I would think that you're actually protecting quite a few items with your zinc in the exchanger, including the exchanger itself.

The electrolysis you're fighting can come from stray current in the salt water and it isn't necessarily coming from your boat (hence the term "hot marina"). Also, the makeup of dissimilar metals immersed in salt water (a conductor) can cause more or less rapid degradation of the "weaker" metal. Isn't the fact that your sacrificial zinc deteriorates rapidly proof positive that it could be some other metal in the vicinity that would suffer if the zinc weren't there?

Food for thought.

Kelly

[msauntry]

If the copper tubing has one side in salt water and the other in fresh/glycol solution, is there still an electric current set up?

I'm guessing the heat exchanger is not made of just one metal, hence the need for the pencil zinc.

[jhwelch]

Kelly, like a flagpole in a strong breeze, my pencil zinc gets a strong flow
of salt water past it, so it is eroded away fairly quickly.

I may know more today; I am hauled out for repairs and am going to
have the heat exchanger cleaned, so will have the end cap off
for the first time since I had this exchanger made about 4 or 5 years ago.