Refurbishing a Zinc Anode

[AlanR]

If your anode lasts for two or three years, it probably is not working effectively. Check the wiring back to the engine, from the actual zinc, not the attaching bolts. It is possible for the zinc to become detached from the steel backing, rendering it useless. You should have less than one ohm resistance in the path back to the engine and other fittings.

I scrub mine with a rotary wire brush, on an electric drill, to remove the white crust, and replace it when it is down to 30% of its original size. After 20 plus years, my bronze prop still looks good, after I scrub the barnacles off it.

I once had some advice from a bystander when I was painting the bottom of my boat with antifouling paint. He said I should paint over the anode, and it will last longer. Of course it will, but do you really want it to? Not this way.

Remember, you are sacrificing it, to protect all other fittings in contact with the sea.

Alan

[SVRocinante]

Originally Posted by AlanR

...It is possible for the zinc to become detached from the steel backing, rendering it useless. You should have less than one ohm resistance in the path back to the engine and other fittings...

This brings up another question that's been bothering me.
I've met several people that hang a "Zinc" from a line off their boat.

Once again, having only the most basic understanding of how the zinc is supposed to do it's job, I don't understand what possible good it can do to dangle a zinc that is not somehow "connected" to the boat.

info?

[fstbttms]

Originally Posted by SVRocinante

I don't understand what possible good it can do to dangle a zinc that is not somehow "connected" to the boat.

It doesn't do any good. An anode must be in direct electrical connection with the part being protected.

[rwidman]

Originally Posted by AlanR

If your anode lasts for two or three years, it probably is not working effectively. ...........

That's it in a nutshell. It's not connected or it's the wrong anode for the water you are boating in.

[FabioC]

Actually, I tend to disagree with this one.
Salt water is conductive, so strictly speaking the anode is always connected to your boat, as long as it is in the proximity of it.
This is confirmed by this other observation (ask the guy who changes the zincs for a living at your marina): if the boat in the slip next to yours has no working zincs, your zincs will consume more rapidly, because your neighbor's boat starts getting to use yours (assuming that you have them, and only when the boat is next to yours, of course). Your zincs are certainly not connected with your neighbor's boat, but still, they work for his boat.

[fstbttms]

Originally Posted by FabioC

...(ask the guy who changes the zincs for a living at your marina)

That would be me.

Originally Posted by FabioC

...if the boat in the slip next to yours has no working zincs, your zincs will consume more rapidly.

Nope, not even remotely true. Twenty three years in the business and over 30,000 hulls cleaned. Have never once seen evidence of this.

[Rough Magic]

Electrical connection is essential. Here's what BoatUS has to say

BoatUS – BoatTech – Sacrificial Zincs by Don Casey

Anodes (zincs) are made of different alloys for protection of different kinds metals and in different types of water; salt, fresh, or brackish. I learned this the hard way with an outdrive.

[boatpoker]

Once an anode is encrusted with any calcareous deposit it is "insulated" and can no longer function as it should. Many people grind an anode in place and clean off the calcium, this is only half the job. The underside of the anode ( the contact side ) must also be cleaned to ensure good electrical connection to the metal it is connected to.

A simple test (on the hard) is to set your multimeter to ohms and touch the anode with one probe and the metal to which the anode is affixed with the other. You should see a reading of less than 1.0ohm with 0.0ohm being ideal.

Many boats in fresh or brackish water using zinc anodes develop a calcareous coating veryy quickly and render their zinc anodes useless. The upside is they will last for decades
.... Retired Certified Corrosion Analyst.

[a64pilot]

As far as recasting zincs, first there is a health issue as molten zinc gives off some kind of poisonous gas, but also the metal is a different alloy as I believe the zinc wastes away leaving behind other metals, melt it down and it’s a different alloy, that may not provide the correct protection.

[boatpoker]

Originally Posted by a64pilot

As far as recasting zincs, first there is a health issue as molten zinc gives off some kind of poisonous gas, but also the metal is a different alloy as I believe the zinc wastes away leaving behind other metals, melt it down and it’s a different alloy, that may not provide the correct protection.

+1

Also any impurities in the casting could create a galvanic cell within the anode.
Best stick with name brand (not Chinese) mil spec anodes where purity is guaranteed.

[newhaul]

Originally Posted by SVRocinante

This brings up another question that's been bothering me.
I've met several people that hang a "Zinc" from a line off their boat.

Once again, having only the most basic understanding of how the zinc is supposed to do it's job, I don't understand what possible good it can do to dangle a zinc that is not somehow "connected" to the boat.

info?

I hang a bar zinc off my boat on a heavy copper wire that is run into the vessel and attached there to the bonding system .

[Bruce K]

I always use galvanized anodes, the are much better!!!!

[frant]

No reputable anode manufacturer will use recycled anodes as a source of raw material. The QA system will not allow this and risks are simply too high. eg Zinc SHG (99.995%) Aluminium AP180 (99.8%) Magnesium (99.95%) and other alloying ingredients are the highest commercial grade purity and are required to meet anode specifications and make anodes that do not passivate.
Our zinc anodes are made in 400kg batches (approx AU$1600 material) one single kilogram of out of spec anode material or the fe pickup from melting down a single recycled anode could render that entire batch as scrap. Alternatively any moisture contained within the oxide coating or in crevices could explode showering employees in zinc.
There is also a huge difference of anode performance between various anode manufacturers as the specification tolerances and manufacturing procedures are tweeked to optimise the anode electrochemical performance.

[nwdiver]

Originally Posted by Kenomac

At $65 for a new primary anode, I decided it was worthwhile to spend 15 minutes refurbishing the old one using a grinder.

It looks fine, I wouldn't have spent the time removing it to spend time grinding it........i replace when necessary

[buzzstar]

Someone else said it, but differently. There are courses for horses, and horses for courses. There are anodes (zincs usually) for salt water, brackish water, and even fresh water. I recall prior discussions, in some depth, on CF, and strongly recommend that you searchers and questioners check there. It can save you a lot of money and grief.