Used zinc annodes

[Mambo42]

I have searched the history of this forum, but could not find anything, so herewith the question.

I replaced all my zinc annodes about 2 months ago, boat went into the water, but was taken out last week again to install the stabilizers. In total I will spend about 1 month on the dry, then the boat will go in the water again.
Obviously all the zinc annodes are more or less new, but what would be the correct thing to do ?
1. Can I leave them the way they are and just keep using them ?

2. Should I clean them with a brush and then keep using them ?

3. Should I just take them all off, throw them away and install new ones ?

Fun part is that over here I hear all three opinions, but nobody is sure about it. If they would be fairly old I would change them, but they are brand new and in very good condition. Worst part is that some of those annodes I cannot even find here.

Appreciat the input.

 

[jgwinks]

If there's growth on them, clean it off. That's it. Being on the boat on the hard isn't much different than being in the package in the store. There's no electrical activity without the sea water.

 

[Old Sea Dog]

I am not an expert on the subject, but from my experience I would not replace them. Unlike some antifouling bottom paints, I do not believe that newer sacrificial anodes loose their effectiveness after a month or two out of the water.
Previous owner of our boat replaced "zincs" when it was hauled for survey. A month later I hauled it to add a coat of bottom paint and work on a few thruhull fittings. Zincs were good so after 3 weeks on the hard we splashed and moved her from Marathon FL to Crisfield MD.

 

[Circumnavigator]

#2 would not be a bad idea, but not necessary. A zinc is good until it is gone, so if your boat lives in a benign electrical environment you can often get more than one year out of them. Replace them if they are half gone after a year.


The lightship Nantucket, across from us at Fintry's berth in Boston, had zincs left after 13 years without being hauled. As steel vessels both the lightship and Fintry had a lot of big zincs.


Jim



Jim

 

[Mambo42]

Most of the zincs look still very good, a little bit of wear on them, but for the rest they are in good condition. The ones on the swim platform are actually the best. Bow thruster has some more wear, but the boat will be out again during the winter season, they only need to hold until mid November / beginning of December.
So I guess I will just keep them, brush them off a bit and leave it at that. As anti-fouling I have copper coat, works perfect, hull was completely clean.

 

[jgwinks]

Yeah. They're good till wasted away down to half or maybe even a quarter of new. If you haul out every winter (I'm in Michigan so that's a given here) just check them in the fall along with all the other underwater stuff. That's the only upside to our short boating season here, we get lots of opportunity and time to take care of these things.

 

[slowgoesit]

Most of the zincs look still very good, a little bit of wear on them, but for the rest they are in good condition. The ones on the swim platform are actually the best. Bow thruster has some more wear, but the boat will be out again during the winter season, they only need to hold until mid November / beginning of December.
So I guess I will just keep them, brush them off a bit and leave it at that. As anti-fouling I have copper coat, works perfect, hull was completely clean.

I'm in the "it can't hurt to give them a light brush and splash her!" crowd, but I want to address another comment you made based on our recent experience.

If one or more anodes are in much better shape, as you mentioned above with the ones on the swim step, use a multimeter and ensure that you have zero,or near zero resistance between all the anodes, and between anodes and any below waterline metal. (rudders, shaft, prop, skeg, through hulls, swim platform supports, etc).

We hauled out last month, and, through the use of a multimeter and some long wires, solved why OUR swim step anode lasted WAY longer than any of the others . . . . for some reason, it was not connected to the rest of the boat bonding system . . . . now corrected.

 

[Mambo42]

I'm in the "it can't hurt to give them a light brush and splash her!" crowd, but I want to address another comment you made based on our recent experience.

If one or more anodes are in much better shape, as you mentioned above with the ones on the swim step, use a multimeter and ensure that you have zero,or near zero resistance between all the anodes, and between anodes and any below waterline metal. (rudders, shaft, prop, skeg, through hulls, swim platform supports, etc).

We hauled out last month, and, through the use of a multimeter and some long wires, solved why OUR swim step anode lasted WAY longer than any of the others . . . . for some reason, it was not connected to the rest of the boat bonding system . . . . now corrected.

Thanks for the tip and come to think of it, am not sure that the swim platform is connected to the rest of the boat system. It was a later add on, but it also has 6 zincs on it. Each prop shaft has only 2. Rudders have 2 each and bow thruster has 1.

 

[Fish53]

Zinc is zinc, if there's some there and exposed it'll work, how long is the question. Just remember it needs a good electrical connection to what it's supposed to protect.

 

[Comodave]

Anodes should be replaced when they are 1/2 wasted away. If they look new then clean them up and launch.

 

[Fish53]

Anodes should be replaced when they are 1/2 wasted away. If they look new then clean them up and launch.

Mass and surface area have a sizable affect on anode life, as does the nature of where you have your boat. In my harbor I have a 2 lb. block zinc and two shaft zincs (1.25"). After about 12 weeks the shaft zincs are almost gone and the block zinc is down to 50 percent. Obviously I put new on every time I launch, this may not be necessary depending on where you operate and the type of anode used.

 

[Comodave]

In my area, Great Lakes, I have people tell me that their anodes last for years with no wastage. I tell them that they want the anodes to gradually waste away. And that the reason theirs are not wasting away is that they are using zinc anodes. The I explain that zinc anodes don’t work in freshwater and that they need either aluminum or magnesium anodes.

 

[jgwinks]

In my area, Great Lakes, I have people tell me that their anodes last for years with no wastage. I tell them that they want the anodes to gradually waste away. And that the reason theirs are not wasting away is that they are using zinc anodes. The I explain that zinc anodes don’t work in freshwater and that they need either aluminum or magnesium anodes.

True. Fresh water is not nearly as electrically active as salt. The zincs don't waste away but neither do your underwater metals, hopefully. This probably masks a lot of electrical problems and if those boats ever move to salt water they're in for a rude awakening. My "zincs" are actually aluminum, good for fresh or salt. Magnesium is for fresh only, it's too active for salt water.

 

[OldDan1943]

For recreational boats, replacing zincs is cheap insurance.
As I recall, the US Navy used the 1/3 rules for replacing zincs rule. The also used something akin to a chipping hammer to insure the zincs were not a shell.

 

[klee wyck]

I hauled in March for the stabilizer project on LIBRA after 2 1/2 years since new zincs. Steel boat, lots of zinc. They looked good so I put her back in the water without touching them. I will haul again in a couple of years.

 

[Fish53]

True. Fresh water is not nearly as electrically active as salt. The zincs don't waste away but neither do your underwater metals, hopefully. This probably masks a lot of electrical problems and if those boats ever move to salt water they're in for a rude awakening. My "zincs" are actually aluminum, good for fresh or salt. Magnesium is for fresh only, it's too active for salt water.

While aluminum does work in saltwater I've found that it forms a layer of aluminum oxide after a short time and becomes passified. Not an issue if you can clean them off frequently. Anodes can and should be tested with an ohm meter before launching or anytime their function is in question.

 

[Gypsy Diver]

Number 2 is the correct answer.

 

[Steve DAntonio]

Corrosion industry wisdom dictates that anodes should be replaced when 50% depleted. Past that point their ability to drive voltage of protected metals -200 mV is too far diminished. If a vessel is hauled and anodes are at 70% I'd change them.

If anodes seemingly last "forever" there's something wrong, they usually aren't making contact with the metal they are supposed to be protecting. If you have growth on them, that's also an indication they are not working.

You do not need to replace anodes if they are less than 50% depleted and being out of the water will not hinder them from working when relaunched.

 

[Hobbit]

Its very important to brush them with a clean stainless steel wire brush that has not been used to brush any other types of metal or it will prevent the zincs from working properly. You should get a least a year out of them....if not you might have some stray current from another boat or yours.
IMO ....Nigel Calder's book on boat maintenance is the gold standard. Lots of good information.

 

[Steve DAntonio]

Only non-metallic abrasive devices should be used to clean anodes, ScotchBrite, or Nylon bristle brushes for instance. Stainless is too aggressive and over kill, and it can embed stainless in the anode, which can affect its protection of the metal to which it's attached.

 

[luna]

What is the point of brush cleaning the slightly used zinc anode when you are on the hard?

Who here cleans their anodes regularly while the boat is afloat?

 

[CharlieO.]

What is the point of brush cleaning the slightly used zinc anode when you are on the hard?

Who here cleans their anodes regularly while the boat is afloat?

I just wiped mine down (aluminum) a couple weeks ago while were anchored and swimming. One on the rudder and one on the transom.

 

[Hobbit]

Thanks sounds like good advise.