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Shaft anode small bubbling

Dec 13, 2010
123
Hake 32RK Red Bank
The zinc is an anode in the battery cell. It is emersed in water- the electrolyte. The pressence of a voltage difference actoss the cell drives a current. Off gassing iccurs at both the annode and cathodes of the cell. One stream will be Hydrogen the other oxygen. The more vigorous the bubbling the more current that is flowing. Thats how it works. Now as to why the potential difference could be everything from potential due to different metals in close proximity to external stray voltage due to improper wiring etc. Good luck
 
Feb 26, 2011
1,196
Achilles SD-130 Alameda, CA
And if there aren't two streams of bubbles? Because in my experience, there is invariably only one.
 
Jun 2, 2016
4
Hunter Legend 36 West Mersea
The area of the anode is small. The area of the cathode (shaft, prop, keel, hull fittings, etc.) is large. You will see the oxygen at the anode but the hydrogen generated across the other various surfaces will be more difficult to spot.
If you clean up one small area (e.g. a bit of bronze prop) you will see the hydrogen being given off...
As the anode does its job, the reaction will slow and the bubbling will get less furious; if it stops completely, you are in trouble because it will no longer be offering sacrificial protection of all the cathodic parts.
By the way zinc is zinc. Chinese zinc has the same galvanic properties as American zinc - and you have to thank an Italian for discovering those...
 
Sep 24, 2013
36
looking looking Corpus Christi
As mauruuru said "Now as to why the potential difference could be everything from potential due to different metals in close proximity to external stray voltage due to improper wiring"...

This usually comes from some rewiring project that used inferior wire... i.e. the crap you buy from Walmart is NOT meant for use on your boat.

I had to replace several yards of wire that was not up to the task of being on a boat, including the rewire job with 6 splices to the running lights on the bow. Only 6 you say?... on 27 foot boat I reply.

Point? My anodes no longer crumble. People cut corners when the boat is a weekend use type of thing... And yes I had to replace the wire that went up to the newly-installed-before-I-bought-it masthead light.

I first realized there was an issue because of the corrosion that practically ate the fresh water cooling tank for the engine, the anode in it didn't even last a summer...
 
Jul 26, 2015
42
Watkins 29 Ft. Lauderdale
Today I drove underwater and clean ed the hull. While there I changed out the shaft anode. I noted the new anode was bubbling!!?? Really small bubbling trailing out from between the two halves anode gap. What gives?

It had beans for dinner last night?
 
Feb 14, 2014
5,050
Hunter 430 Waveland, MS
By the way zinc is zinc.
Well not if it is for a sacrificial anode.
It takes a pinch of Indium to prevent zinc form forming Zinc Oxide. Here is the USA specifications for the anode alloy. Also the way the zinc is cast is a key. I am not pointing fingers at any country. I have done my homework on suppliers here. I suggest you do the same on your suppliers.
http://stoprust.com/sacrificial-anodes/
Minor gassing should be only when you are approaching "steady state" protection. That is what you see when you brush and expose new propeller metal.
Basically it will stop when the Zinc anode works.
If it continues...
Do an electrical survey.
Jim...
 
Feb 14, 2014
5,050
Hunter 430 Waveland, MS
Dammit Jim I'm a doctor not an electrician!
I am almost a Doctor (of Chemical Engineer;)).
Doctor Laser, it is just a another type of a chemical battery, discharging. Hopefully the zinc is the source of electrons and NOT your prop.:biggrin:
Jim...
 
Jan 30, 2012
1,054
Nor'Sea 27 - "Kiwanda" Portland/Anacortes
Dammit Jim - Indium is for aluminum anodes not zinc.

See US Military Specification A-18001K for zinc and US Military Specification A-24779 for aluminum.

Additional tip - keep/buy zinc anodes from plastic containers - no metal. A very small amount of iron will render them passive thus useless.

Edit: Another additional tip - Do not clean zincs with a wire brush for the same reason.

Charles
 
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Feb 14, 2014
5,050
Hunter 430 Waveland, MS
Dammit Jim
Well who you told my first name is Dammit and my Middle name is Jim. My parents, friends and Marine Drill instructor always called me "Dammit Jim":laugh:

Well the Military 1983 :snooze:zinc anode spec was worried about Iron contamination and shape (as I noted above). The Aluminum anode spec 1992 has Indium. Guess why? Indium also prevents Aluminum from forming Aluminum Oxide which "passivates/stops" the Aluminum from corroding (check out you Aluminum Mast).

The newest zinc anode alloys have Indium in them. Refer to the spec in my post#26.
But my point is still...
a Zinc anode (like Aluminum anodes) are are alloys and not pure metals.
I wonder why you didn't use my first name in this thread?
http://forums.sailboatowners.com/index.php?threads/aluminum-anodes.177362/#post-1280252
Take Care and refer to my post#5 about my advice...:)
Jim...

PS: Most common metals form an Oxide passivate the surface. We don't want our sacrificial anodes to passivate.
 
Jan 30, 2012
1,054
Nor'Sea 27 - "Kiwanda" Portland/Anacortes
Well who you told my first name is Dammit and my Middle name is Jim.
Fact of matter is no one really gets to choose the anode chemistry because the foundry and its actual spec compliance conspire to give us what is on the shelf.

My point on Indium was diminutive and trivial (means very small) but Indium is no part of an alloy recipe for zinc anode if the zinc alloy is supposed to be military specification compliant.

In any case, one needs to see a 200 mv negative shift from no anodes to good anodes.

Hence -- embrace measurement and reject guess work. In general, about 800 mv negative shaft potential is a pretty good index for an FRP boat well zinced.

Very much to the contrary for a wood or metal boat by the way.

Charles
 
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Oct 29, 2005
2,121
Hunter Marine 326 303 Singapore
Question is the boat plugged into shore power?
Yes. Boat was plugged in to shore power when at berth. I'll try to take a look this weekend to see if its still bubbling. If it still do, I try capture a video of it.
 
Jan 26, 2016
11
Hunter 41 Huntington,
I have a question, I have a 2006 Hunter 41AC with Isolators (which hum when boat is on shore power) and installed a single Zinc on my shaft September 1st last year and it was gone by haul out November 1st. I added two zincs to the shaft his year at commissioning April 1st and just had the bottom cleaned and both were gone August 1st.. Diver replaced it with a single. I've replaced the 30amp receptacle on board and the marina replaced the dock side as well and I purchased a new 30amp cable. My old Hunter 29 had the zinc just about last from April till November one finger over but I only would plug in once or twice a month to charge the bateries. Has anyone had the isolators stop functioning? How can I test them or am I looking at the wrong cause? Help!
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Bill; Yes, an isolator can definitely blow. My instruction manual includes methods to test the isolator. That hum is suspicious.
 

Oliver

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Mar 16, 2014
114
Oday 25 Bradenton Beach Florida
So we live on a oxygen filled rock, energy causes oxygen to escape, it gets in the way, bubbles under water etc... Who would of guessed. So I take two 2ft iron rods. I hit them together and create a spark. You may not see the spark but the energy was created none the less. If I hit them together 17 million times a second and plug into it I can feed a city all the power it needs, old school. Scientist fine tune, us crazy people invent. I got more, come get it. ⚓⚓⚓ good luck with the bubbles for real.
 

Allex

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Aug 1, 2016
4
Almond 31 Havre de Grace
I have seen this at our marina when plugged in there we found a positive charge in the ground circuit this was causing bubbling at the anode the fix was unplugging the shore power and the bubbles stopped
 
Feb 14, 2014
5,050
Hunter 430 Waveland, MS
I have seen this at our marina when plugged in there we found a positive charge in the ground circuit this was causing bubbling at the anode the fix was unplugging the shore power and the bubbles stopped
That comes from another source, who perhaps has a incorrect grounding to the ground circuit (green wire).
In this case, the bubbles are Hydrogen.
Jim...