Determining zinc use

[Mkfcdl]

Quick question:

I used to have (at a different marina) problems with zincs -- a zinc fish would last about 3 months. Checked my boat and fixed some problems, still zinc use. Now, I'm in a different marina and my zinc fish doesn't get used up and in fact just gets growth. I checked the zinc fish's connection to my bonding system with voltmeter/ohmeter--good solid connection.

So, does growth on the zinc mean it's not getting used or should I keep it cleaned as it just may be very slowly used up?

[sailingdog]

It really depends on the water in your new marina. Zinc-based "zincs" are not recommended for freshwater, as they will grow a coating of zinc oxide and stop to work. If your new marina is brackish, with a fair amount of freshwater, I would look at Aluminum "zincs" instead. Magnesium "zincs" are too reactive and should only be used in pure freshwater...not brackish.

[Mkfcdl]

Thanks for the info on brackish water with zincs. This marina probably is a bit brackish but it's enough to run a LectrSan so must have decent salt content.

Since my last post, I measured the current flow between the zinc fish in the water and my bonding system--about 6 milliamps and 0.3 volts. Not much but something. So I think I'll keep my zinc fish in and just give it a good scrapedown every so often.

[Fstbttms]

Originally Posted by Mkfcdl

So, does growth on the zinc mean it's not getting used or should I keep it cleaned as it just may be very slowly used up?

It is common for "fish"-type zinc anodes to get fouled fairly rapidly. This is a large zinc and should last quite a long time, everything else being as it should. Do not take the growth on the zinc to mean that it is not working, but do check it for signs that it is depleting (as it is supposed to) when you clean it.