Zinc Versus Aluminum

Hi All,
I spend very little time in fresh water and am currently up in the Anacortes WA area. My zincs seem to be going a bit fast, especially my pencil zincs. For best protection would you recommend keeping with Zinc or Aluminum? I have tested most of my boat I think the marina is just a bit hot. Im getting 4 months on a 2" pencil in the engine.
Thanks in advance!
AC

Arthurc said:

Hi All,
I spend very little time in fresh water and am currently up in the Anacortes WA area. My zincs seem to be going a bit fast, especially my pencil zincs. For best protection would you recommend keeping with Zinc or Aluminum? I have tested most of my boat I think the marina is just a bit hot. Im getting 4 months on a 2" pencil in the engine.
Thanks in advance!
AC

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If the anodes are going more quickly then they are doing their job. I check my engine anodes every 3 months and replace typically every 6-9 months. I did just switch from zinc to aluminum anodes last month since I've started doing a fresh water flush of the engine when I return to the dock. So my engine sits with fresh water in its cooling system instead of salt water.

Engine zincs should not be affected by whether a marina is "hot" or not if you mean leaks through the AC ground wire from another boat back to your boat. Your hull zincs should be the only ones affected by a hot marina.

On my two Yanmar 6LYs over a ten year period, some zincs would waste at about that rate, probably those in an area where the raw water didn't drain down and was left full of raw water between engine runs. You learn which go first and check them more often.


Hull zincs would last a little longer 6-12 mo and I either kept my boat on a mooring where shore power leaks couldn't affect me or in an isolated slip with no adjacent boats nearby.


DHays makes an interesting observation, one which led to a heated exchange some years ago between me and the venerable Tony Athens. If you fresh water flush then maybe you need aluminum engine zincs because 95% of the time they sit in fresh water. Aluminum works better than zinc in fresh water.

David

If you're spending time in fresh water, then I'd recommend aluminum. Zinc just isn't good in fresh water any more than magnesium is in salt water. Aluminum handles both.

Ok Zinc it is.

Thoughts on what is causing my zincs to go so quick? I'm at every 9-12 months on the rudder zincs but these feel super quick. In fact I think I had the last service in June which means about 2 1/2 months to be 1/2 gone. (2" 1/2 zinc)

AC

djmarchand said:

DHays makes an interesting observation, one which led to a heated exchange some years ago between me and the venerable Tony Athens. If you fresh water flush then maybe you need aluminum engine zincs because 95% of the time they sit in fresh water. Aluminum works better than zinc in fresh water.

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I read through that entire thread on Boat Diesel between you and Tony. Notice, I elected to start using AL anodes rather than zinc when I started doing the fresh water flush.

One of the concerns is that many knowledgeable folks report that zinc anodes develop a surface coating that becomes less reactive when used in situations where they are intermittently exposed to fresh water. Some boaters think this is a good thing as they don’t have to replace them since they then last a very long time. However, I don’t want my anodes to last a long time. They are supposed to be sacrificial anodes after all.