Zincs- More is better?

cantolina
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Posts: 16
Joined: Mon Mar 25, 2019 4:21 pm

Zincs- More is better?

Postby cantolina » Wed May 08, 2019 10:42 am

I'm replacing zincs on my 32' Sedan FB, and currently, there is 9' ! of anodes on each side of the keel, and the rest are as typically specified.

What would be the reason for 9', vs the recommended 3' on the keel?

Is more better, or is this overkill? Just curious before I order from Boatzincs.com

Chuck
Chuck
32' Sedan FB
Venture II
Soon to be slipped in Port Colborne, ONT

jralbert
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Re: Zincs- More is better?

Postby jralbert » Wed May 08, 2019 12:52 pm

Overkill is not good according to all I've read. It sets up what I'd describe as an inbalance. A "little" more won't hurt but tripling is not warranted from either protection or cost considerations. I wish I had a citation for you - if I dig one up, I'll put it here

(An update: David Pascoe, a surveyor, maintains a web site with lots of useful info. I can't tell you whether Pascoe is the reigning authority on everything he writes about but he seems to make sense on many issues. In his section on corrosion (which is directed at boats in general, not aluminum M's specifically) he writes "...Over zincing, putting too much zinc, on causes the opposite problem. It will reverse the flow of current in the other direction and actually cause corrosion. Over zincing is discernible when you find your props all covered with a coarse layer of zinc oxide. It will feel like sandpaper. This condition will reduce your boat's speed significantly and increase fuel consumption. I'll bet that statement got your attention!!!..."

So, there's one viewpoint.
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

cantolina
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Re: Zincs- More is better?

Postby cantolina » Wed May 08, 2019 1:21 pm

Thanks, Joel.

I had a hunch. Thanks for the reference too. Good reading.
Chuck
32' Sedan FB
Venture II
Soon to be slipped in Port Colborne, ONT

CallMeCaptain87
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Re: Zincs- More is better?

Postby CallMeCaptain87 » Thu May 09, 2019 3:57 pm

I am replacing my anodes as well. I ordered some extra anode material to cut into spacers to put behind mine. I will drill them and use them like a washer between the anode and the hull. This will keep the anodes in contact with the hull where bolted, but leave a space behind them to allow the whole anode to be exposed on both sides.
1990 37' Marquis
Twin 454
Louisville, KY

jralbert
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Re: Zincs- More is better?

Postby jralbert » Thu May 09, 2019 5:07 pm

Hmmm...I'm not sure that is right - though it may be. OK, class, a homework assignment - someone look up the contact question. I always believed the more contact between zinc and surface the better. No paint, of course, on the zinc and where it contacts the surface. Here is what Boat US says (I have done my part of the homework):
Electrical contact is essential---
There is an unfortunate misconception that a sacrificial anode can be mounted anywhere, even hung over the side on a string, and it will still perform its appointed duty. That is dead wrong!

For a zinc anode to provide any protection, it must be in electrical contact with the metal being protected. The conductivity of the water is not adequate. We need low-resistance, metal-to-metal contact — either by mounting the zinc directly to the metal being protected or by connecting the two with a wire. A hanging anode can provide protection if it is connected by a wire to the metal being protected.

Where the zinc is mounted directly to the protected metal — bolted to the side of a metal rudder, for example — it is essential to make sure the surface under the zinc is bare and bright before the anode is installed. This is to ensure good electrical contact
-joel-
former owner 1988 '32 FB Sedan
Chesapeake Bay
twin 318 / 240 hp
Potomac MD

cantolina
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Posts: 16
Joined: Mon Mar 25, 2019 4:21 pm

Re: Zincs- More is better?

Postby cantolina » Sat May 11, 2019 4:44 pm

I agree. Although I am kind of a newbie to big boats, my understanding of the science is that direct, full-surface contact is required for the anode to do its work. "high-impedance-air-gaps" do very little in the electrical world.
Chuck
32' Sedan FB
Venture II
Soon to be slipped in Port Colborne, ONT

CallMeCaptain87
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Joined: Sat Aug 20, 2016 5:12 pm

Re: Zincs- More is better?

Postby CallMeCaptain87 » Sat May 11, 2019 6:32 pm

The direct contact would be made through the spacers. The purpose of the gap is to allow more surface area of the anode (that is in contact with the hull) to provide protection. When bolted directly to the hull you have the exact same thing as what I am talking about, only it gets buildup behind the anode and the painted areas where it is not bolted. I agree if not connected to the boat it does nothing.
1990 37' Marquis
Twin 454
Louisville, KY

barkleydave
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Location: Kentucky

Re: Zincs- More is better?

Postby barkleydave » Sun May 12, 2019 11:47 am

There is still confusion regarding galvanic protection. I have used a mag. hang over anode for 15 years now to bring my numbers up. I have the correct anodes on my 29 provided by BoatZincs.com. While the numbers increase they still fell short of the recommended -.95- -105 . mv By using the mag anode it brings my number up to the correct range. What some may be confusing is the continuity factor as mentioned in an earlier post. Just hanging an anode for the side on a FG boat it pointless. It must have continuity. Now our Big M's do just that. By attaching the cable to a stanchion for example the stanchion is bolted directly to the aluminum deck and completes the circuit. If I remove anode the numbers drop immediately!

I hang mine over the side on the stern directly over the location of struts, rudders and props. I have NO evidence of galvanic corrosion anywhere on my Big M. I pulled the boat late last summer for a complete bottom strip and repaint and everything was absolutely perfect. (We did find where a strut bearing had come loose and almost backed completely out of the strut! (caught that in time!)

When we pull the boat (every 4th season) we remove the bar anodes clean and re-install or replace as required. Even with clean anodes making complete contact with the hull numbers improve but only for a short time.
Now you can expect your numbers to run slightly lower in fresh water. (the cleaner the water the less continuity)
Clean your over the side anode at least once a month and use ONLY a stainless steel brush! My anode is full of deep pits which shows it is working and has been for at least the past 9 years and still has plenty of life left.

In summary; by connecting a mag (fresh water only !) to a stanchion protection is thereby provided. " A hanging anode can provide protection if it is connected by a wire to the metal being protected."
1987 Marinette 29 FB Sedan
Retired Boat Accident UL and USCG trained investigator
Retired USCG Captain

cantolina
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Posts: 16
Joined: Mon Mar 25, 2019 4:21 pm

Re: Zincs- More is better?

Postby cantolina » Wed Jun 05, 2019 7:10 am

Has anyone ever used a carbon conductive assembly grease when installing new anodes? Just seems like it would be a good idea?
Chuck
32' Sedan FB
Venture II
Soon to be slipped in Port Colborne, ONT

cantolina
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Posts: 16
Joined: Mon Mar 25, 2019 4:21 pm

Re: Zincs- More is better?

Postby cantolina » Wed Jun 05, 2019 6:24 pm

I spoke to a fella at boatzincs.com who told me to absolutely not use conductive grease. Metal to metal contact only.

So there it is. :)
Chuck
32' Sedan FB
Venture II
Soon to be slipped in Port Colborne, ONT