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Old 02-15-2013, 10:51 PM   #1
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Zincs

I was doing some routine maintenance today. Changed out the pencil zincs on the heat exchangers. Donít know how long the old ones were in there (the PO didnít keep records or notes). More than a year for sure. Zincs were gone. The tube bundle openings however, were surprisingly clean and open.
Picked up some spares with the new ones. KJ
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Old 02-16-2013, 04:29 AM   #2
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Wow! Good thing you checked them!

I have a related question. Recently my boat was moved from saltwater to a freshwater marina. We keep her on the Freemont cut east of the Ballard Locks in Seattle. We intend to do most of our boating in Puget Sound though. Question: should I change to magnesium "zincs"? Or doesn't it matter much? I suppose I could install both on the shaft and rudder, but the heat exchanger has only one zinc.
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Old 02-16-2013, 07:19 AM   #3
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Or doesn't it matter much?

I would be more concerned with how the energized water is if you keep her in a marina.

This can be measured.
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Old 02-16-2013, 10:01 AM   #4
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Question: should I change to magnesium "zincs"? Or doesn't it matter much?
I can't answer your question with any factual accuracy but if it were me I'd continue to use the zincs. What I can say, with assurance, is that I absolutely love the area you slip your boat in! Talk about "Boat Porn"! There's just about every type of water vessel known to man there.
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Old 02-16-2013, 11:31 AM   #5
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Would there be a problem if dielectric grease were applied to the threads?
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Old 02-16-2013, 12:08 PM   #6
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Magnesium "zincs" do a better job in fresh water.

Dielectric grease won't hurt anything and may make it a bit easier to tighten up and remove later.

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Old 02-16-2013, 01:24 PM   #7
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Would there be a problem if dielectric grease were applied to the threads?
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Since the anodes need to make electrical contact with the metal they are supposed to protect and since dielectric grease is an insulator, it's probably not the best choice.

Screwing the anode into place would probably scrape away enough of the grease to make electrical contact, but why chance it?

I think you would do better to install them with no lubricant.
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Old 02-16-2013, 01:26 PM   #8
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"Zincs" that are not made of zinc are not "zincs". They are "anodes". Anodes made of zinc are anodes as well.
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Old 02-16-2013, 01:39 PM   #9
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Thanks, I'm aware of that which is why I put the word zincs in "quotes", rather than say cathode.
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Old 02-16-2013, 01:50 PM   #10
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Would there be a problem if dielectric grease were applied to the threads?
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I keep one of those little squeeze tubes (think: ketchup packet) of spark plug grease I pick up at the check-out counter at the local auto parts store in my toolbox for that very reason. Haven't had to buy a brass base for my pencil zinc in three years.

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Old 02-16-2013, 02:17 PM   #11
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Copper-based never-seize on the threads is a good idea. I have a set of tapered pipe-taps which are ideal for cleaning the hole in the brass plug and the hole in the heat exchanger. Clean the male threads on a rotary wire brush.
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Old 02-16-2013, 02:24 PM   #12
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From my understanding of dielectric grease and threads is it fills voids but doesn't prevent continuity between the threads and the threaded hole as the threads eventually make enough contact.

That said...most advice is no sealants, etc..

But always trying to "better" standard thinking...if you do a continuity check between the brass cap and the part you are trying to protect you should be OK...I forget what number of ohms it should be under but is probably available in searching the web. I just read 1 ohm as being max and should be as low as possible...hopefully less than 0.1 ohm.
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Old 02-16-2013, 09:14 PM   #13
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Wow! Good thing you checked them!

I have a related question. Recently my boat was moved from saltwater to a freshwater marina. We keep her on the Freemont cut east of the Ballard Locks in Seattle. We intend to do most of our boating in Puget Sound though. Question: should I change to magnesium "zincs"? Or doesn't it matter much? I suppose I could install both on the shaft and rudder, but the heat exchanger has only one zinc.
I was just reading about this topic in the latest issue of Passagemaker (March 2013). Steve D'Antonio has an article about corrosion control and among the many items he wrote about, he suggested that using aluminum anodes are better than zinc in both fresh and salt water with aluminum having better electrical characteristics than zinc.

He also wrote that when zinc is exposed to fresh water it gets a coating on it that inhibits its usefulness when going back to salt water. I didn't know that and here in the PNW it is not uncommon for boats to have that scenario where they moor in fresh water and cruise in salt water.

The good news is when I was in the Fisheries store this morning I was told that aluminum anodes are about half the price of zinc anodes.


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Old 02-17-2013, 03:00 AM   #14
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Thanks Ron! Sounds like good advice in my situation to change from zinc to aluminum.

As for dielectric grease, since it is an insulator I would refrain from using it on threads, but I would use copper based grease instead.
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Old 02-17-2013, 03:31 AM   #15
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Here's some additional information about aluminum, from the February issue of a local publication

digital.turn-page.com/i/106931/82
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Old 02-17-2013, 03:42 AM   #16
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Here's some additional information about aluminum, from the February issue of a local publication

digital.turn-page.com/i/106931/82
Thanks Chuck!
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Old 02-17-2013, 08:06 AM   #17
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I would probably change to aluminum anodes as I am up the river about 12 miles from the ocean but I still have a spare set of zinc anodes and during the year my diver changes anodes as necessary. I would have to find a way to make sure he used aluminum as well or I would end up with a mixed set.
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Old 02-20-2013, 08:22 AM   #18
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The good news is when I was in the Fisheries store this morning I was told that aluminum anodes are about half the price of zinc anodes.


Ron
Ron, that's interesting... but I guess that might be the case depending on where you get your zincs...

I read an article yesterday that was linked by go2marine...and the zincs they were talking about were "Navalloy"....that only have about 5% zinc, the balance being primarily aluminum.... While they look interesting.... I did note that these zincs were the same price as the "all" zincs.....except on this site where I buy my zincs....

100% Zinc:
USAzincs.com :: Shaft Anodes-Barrel Collar :: ZINC for Salt Water Use :: X-7 SHAFT ZINC ANODE-CAMP CO. 1-1/2"

Navalloy zinc:
USAzincs.com :: Shaft Anodes-Barrel Collar :: ALUMINUM for All Water Types :: X-7 ALUMINUM SHAFT ANODE 1-1/2"

The navalloy zincs are reputed to last 30% longer or more than 100% zincs. It would be interesting to find out if they actually do...since it could effectively make them a little more cost effective....
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Old 02-20-2013, 08:54 AM   #19
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......... The navalloy zincs are reputed to last 30% longer or more than 100% zincs. It would be interesting to find out if they actually do...since it could effectively make them a little more cost effective....
Only if they are still protecting your underwater metal.

I don't know how we figure that out, but I don't want to save money on anodes only to see my prop eaten away.
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Old 02-20-2013, 10:31 AM   #20
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Thanks Ron! Sounds like good advice in my situation to change from zinc to aluminum.

As for dielectric grease, since it is an insulator I would refrain from using it on threads, but I would use copper based grease instead.


I would not change to aluminum if the boat is moored in fresh water most of the time. Galvanic rating of zinc is 3 and aluminum is 7. Might be Ok to change to aluminum if the boat was in salt and the zincs where going to fast. Why would you want to go to a high galvanic rating if the zincs are lasting and working?


We where moored at the very south end of lake union for 11 years, going back and forth between the fresh and salt , Zincs lasted 3 to 5 years. In Everett brackish they last 3 years if lucky. In fresh make sure your boat does not have any stray electricity as fresh does not conduct electricity very well so there is a higher change a person can get an electric shock in fresh water.

When we retire we might moor the boat back on fresh water. The reason we are moored in Everet, I hated the locks, and the water is brackish, first several feet are fresh and changes to salt about 4 ft. So with a 6 ft draft the majority of the boat sits in fresh water and its only the deep keel that gets growth. The only growth you will get in fresh water is green slime.

Anyway, I would not change to aluminum!

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