Reconstituted zincs

[David Mathis]

For the price of zincs, do you really want to go through that process. They're relatively cheap and in fume form, zinc is a significant health risk. Zinc is easy to find; most of the new wheel weights are zinc. EPA stopped the use of lead wheel weights a few years ago.

[GrowleyMonster]

Originally Posted by Jono as 2234

I have a number of old, partially depleted, zinc anodes lying around. I'm wondering if I can melt them down and re cast. I have a small foundry set up in my workshop, and it would be a trivial task to form new teardrop anodes.
Any chemists on line?

Jon

Like Pilott said, zinc sickness is a real thing. It won't kill you but it will make you miserable for days. I have welded a lot of galvanized steel and caught a whiff now and then. Blegh! See to your ventilation. Some sort of hood or helmet with air supplied would not be out of place. A respirator is not good enough. You will need a good flux. Borax might work, not sure.



You really won't be saving much money, though. Sure you want to do this?

[Old fella]

Originally Posted by Bruce K

My previous boat has a custom shaft/prop anode, a mould for the two halves came, and went with the boat. Both the PO and me cast/recycled said anode for at least 20 years with no corrosion problems for either shaft or prop. I just scrounged old anodes from the slip skip.

Yep, my brother in-law used to do the same thing for his 60 ft steel cat, saved himself a small fortune over the years.

[1ercru]

Every zinc anode we remove we put in the chain locker with our galvanized chain. No disposal issues they just keep doing what do until they disappear.

[slug]

Originally Posted by Old fella

Yep, my brother in-law used to do the same thing for his 60 ft steel cat, saved himself a small fortune over the years.

If your anode is poorly formulated and poorly built it will last forever because it is inert

[Old fella]

Originally Posted by slug

If your anode is poorly formulated and poorly built it will last forever because it is inert

Hi slug, yeah, I didn’t say they lasted forever, they were big anodes, and would get 2 years out of them, over the years the zincs did what they should and never had any problems with any electrolysis.

[Toccata]

I asked this question of an anode manufacturer, Maddox, in Aus (at the last Hobart Wooden Boat festival)
The reply fwiw (given it was delivered by a manufacturer with a vested interest) was: The critical ingredient has been lost from an expired anode, the remainder may be reconstituted into an anode shape, but the composition will be different/incorrect to offer proper protection.

[RaymondR]

It's easy enough to check.

Hang a new as manufactured anode in a tin can of water and note the voltage produced then one of the recast ones and see if the voltages compare. If they are the same size and surface area the m amps should also compare.

[boatpoker]

Originally Posted by Jim Cate

I see no reason that the Cd and Al components will be missing from any sound material from the old anode.

Jim

Whether zinc, aluminum or magnesium anodes they are all alloys made from different metals and all these metals have different voltage potentials.
For example, the aluminum in a zinc anode has a higher voltage potential than the zinc, so it depletes faster and is likely gone by the time you melt down an old zinc anodes.

Unless one has a degree in metalurgy and a substantial lab, you have no idea how much of these other metals are gone when a zinc is depleted nor do you know what that effect that will have on the overall voltage potential of the alloy.

Since anodes work according to their voltage potential it's kind of important.
Not life threatening but believing it's any more than a WAG is just more dock talk.

[rslifkin]

A melted down old anode won't be the same as a new one. But it's possible to test voltage potential and determine if it works well enough.

[Jim Cate]

For example, the aluminum in a zinc anode has a higher voltage potential than the zinc, so it depletes faster and is likely gone by the time you melt down an old zinc anodes.

How does the Al, say, get removed from the sound, untouched metal below the surface of the anode? And if it was thus removed, how can an original anode continue to work once its surface has begun to erode? Yet anodes continue to provide protection until mostly consumed. And if they are still capable of offering protection when partly consumed, why can't one simply re-cast them (having removed all the surface crap)?

I'm not following the logic here... can you explain?

Jim

[RaymondR]

Originally Posted by Jim Cate

How does the Al, say, get removed from the sound, untouched metal below the surface of the anode? And if it was thus removed, how can an original anode continue to work once its surface has begun to erode? Yet anodes continue to provide protection until mostly consumed. And if they are still capable of offering protection when partly consumed, why can't one simply re-cast them (having removed all the surface crap)?

I'm not following the logic here... can you explain?

Jim

You are right Jim, it's all happening on the surface which is exposed to the electrolyte ie sea water. Absolutely nothing is occurring within the unexposed metal below the surface except electrons flowing through it and they could do that forever without changing it.

[Dockhead]

Originally Posted by NormanS

. . . In order to do that, it has to be less noble - that's all. . ..

Not so. It has to not only be less noble, it has to not get passivated by a layer of oxidized material and so rendered inert.


Even tiny amounts of iron in the zinc can lead to this.



Which is not to say that you can't make your own zincs successfully. But you would need to start with really pure zinc in the first place and then avoid at all costs getting even tiny amounts of iron into it.


I'm kind of with Fstbttms here, although I think he could have expressed it a bit less abrasively. The price of good anodes from a reputable maker is not a big deal compared to the cost of what they are protecting. For me at least, it's not a good place to save money.

[NormanS]

Originally Posted by Dockhead

Not so. It has to not only be less noble, it has to not get passivated by a layer of oxidized material and so rendered inert.


Even tiny amounts of iron in the zinc can lead to this.



Which is not to say that you can't make your own zincs successfully. But you would need to start with really pure zinc in the first place and then avoid at all costs getting even tiny amounts of iron into it.


I'm kind of with Fstbttms here, although I think he could have expressed it a bit less abrasively. The price of good anodes from a reputable maker is not a big deal compared to the cost of what they are protecting. For me at least, it's not a good place to save money.

Well, You know what, the anodes that I make for my prop work for me, so that's good enough for me. If they work, and do the job that they're meant to do, efficiency and effectively, why should I believe manufacturer's hokum?
But what would I know, I'm just a practical guy.

[Epicurean]

Here's what to do with old zincs. Zinc is an essential mineral for the body. Take your old zincs and react them with gluconic acid. Collect the precipitate on filter paper and dry. Once a week take 60 mg with 500 mg of hydroxychloroquine. That should prevent you from getting Wuhan corona virus and enable you to live longer. It won't do much to protect your boat though. Spit out the cadmium gluconate (but you knew that) so you don't die. Ok So I don't get sued I have to say I'm not a doctor and this is all TONGUE-IN-CHEEK.