Reconstituted zincs

[Ambler]

I make my own zinc anodes. I use expired ones around the boat yard, put them into a pot and fire up my MSR camp stove. The zinc melts and the pure zinc makes its way to the bottom of the pot. I skim the dross off which comes from the outer surfaces of the expired annodes.
I don't hang over the pot during the process and do the job outdoors.
I had to machine a mold for anodes to suit my 2 blade volvo prop as the 2 piece annodes are rarer than rocking horse poop and cost is over $100 dollars special order for a set! I made 5 years worth of anodes last time and they do work well in protecting the special bronze that Volvo uses. So it is well worth the time and effort for me to make.
I had visited an anode manufacturer many years ago in Sydney (Trefco) to see how it was done. I wouldn't work there in that enclosed big roofed space and wonder if the employees are enjoying their retirement.
Yes I know melting lead, zinc or anything else is hazardous. If you do decide to go down the path of DIY anodes, the big warning was to make sure your mold has absolutely no moisture in it before you pour.
Alum alloy anodes are meant for fresh water in my experience, they won't sacrifice and protect only zinc will work in salt water.

[rslifkin]

Originally Posted by Ambler

Alum alloy anodes are meant for fresh water in my experience, they won't sacrifice and protect only zinc will work in salt water.

Aluminum anodes work in salt water just fine, they're slightly more active than Zinc. Magnesium in salt water is bad though, as they're way too active.

[wsmurdoch]

Originally Posted by Ambler

I make my own zinc anodes. .... If you do decide to go down the path of DIY anodes, the big warning was to make sure your mold has absolutely no moisture in it before you pour.

When we were kids, my next younger brother had two sets of lead soldier molds each of which made three soldiers in different poses. We'd get 5 lb pigs of lead from the hardware store, quarter them with an ax, melt the lead, and make two armies. After the battle we'd melt the mamed and parted soldiers and do it all over again. I have been burned and our bedroom furniture scarred by the lead leaping out of a mold that was either wet or had traces of candle wax left behind from smoking the molds to keep the lead from sticking. I developed a great fear of water.

Life was more fun before the Consumer Products Safety Commission.

Bill

[Ambler]

Originally Posted by rslifkin

Aluminum anodes work in salt water just fine, they're slightly more active than Zinc. Magnesium in salt water is bad though, as they're way too active.

Yes sorry you jogged my memory, we used magnesium in the test tank which was filled with (mostly) fresh water. We had a cocktail of different metals in the tank.
What did you mean by Aluminum is more active than Zinc?
On the scale Magnesium is the most anodic then Magnesium Alloys, then Zinc then a few other metals such as Beryllium then comes Aluminium. So sure Aluminium anodes will work but not if you are protecting a yacht leg. Zinc will erode protecting your Aluminum, stainless and bronze but once it has eroded the aluminium will begin to sacrifice.
Zinc seems to sit about right as a sacrificial anode for an annual haul out.

[tkeithlu]

"Life was more fun before the Consumer Products Safety Commission."

Easy for you to say, Bill. You're one of the ones who survived.

I clean aluminum anodes (14 plates plus a prop shaft collar) with a wire brush and bolt them on with stainless steel. No problems. Of course the aluminum is not pure. You think they use the good stuff to make anodes? The silver anode test I do each six months or so says I'm protected. It's just a matter of renewing the exposed surface. The same two sets have been in use now for eight years. The name of the foundry that made them is no longer readable, but they are still structurally OK. Re-casting them would be a PITA, but the OP wants to, he's not incurring any big risks.

[rslifkin]

Originally Posted by Ambler

What did you mean by Aluminum is more active than Zinc?
On the scale Magnesium is the most anodic then Magnesium Alloys, then Zinc then a few other metals such as Beryllium then comes Aluminium. So sure Aluminium anodes will work but not if you are protecting a yacht leg. Zinc will erode protecting your Aluminum, stainless and bronze but once it has eroded the aluminium will begin to sacrifice.
Zinc seems to sit about right as a sacrificial anode for an annual haul out.

Aluminum anodes aren't pure aluminum, they're significantly more effective as an anode than a plain chunk of aluminum would be. Enough so that they can protect aluminum underwater parts. According to the data I can find, in salt water, a silver/silver-chloride electrode will show about -1040mv potential for zinc, -1100 for aluminum (slightly more active) and -1600 for magnesium. Aluminum anodes are an alloy of aluminum, zinc and indium.

[NormanS]

I have a Bruntons Autoprop, which has a very very expensive nose cone anode. Like some others here, I make my own, normally by melting zinc from discarded anodes. I am not at all convinced by those who say that the zinc must comply with a very precise specification. As long as it is a less "noble" metal than the objects that you want to protect, it'll do the job just fine. I use a gas torch, and an iron ladle, and skim off any impurities before pouring. The Autoprop anode is attached to the prop with three nylon screws, and it is worth putting a little paint on the anode, just at the screws, so that the metal round the screws does not erode.

[fstbttms]

Originally Posted by NormanS

I am not at all convinced by those who say that the zinc must comply with a very precise specification.

Yeah, you're right. All those companies going to the expense and trouble of manufacturing anodes to mil-spec don't know what they're doing. But some guy with a butane torch in his garage and a real tight grip on his wallet, he's the expert.

BTW- most Autoprop anodes run between $15-$20. Your time and effort must not be worth a whole lot to you.

https://www.boatzincs.com/autoprop.html

[a64pilot]

Originally Posted by NormanS

I have a Bruntons Autoprop, which has a very very expensive nose cone anode. Like some others here, I make my own, normally by melting zinc from discarded anodes. I am not at all convinced by those who say that the zinc must comply with a very precise specification. As long as it is a less "noble" metal than the objects that you want to protect, it'll do the job just fine. I use a gas torch, and an iron ladle, and skim off any impurities before pouring. The Autoprop anode is attached to the prop with three nylon screws, and it is worth putting a little paint on the anode, just at the screws, so that the metal round the screws does not erode.

Unfortunately I don’t believe it’s made anymore, but Islers Diving used to manufacture an adapter for the Autoprop that attached to the same three screw holes like the Autoprop Anode but allowed the use of a standard “B” prop anode.
I’m sure someone could take a prop nut and drill three holes in it and use that.
Some of the best money I spent as the Autoprop anode is a bad joke.

[NormanS]

Originally Posted by fstbttms

Yeah, you're right. All those companies going to the expense and trouble of manufacturing anodes to mil-spec don't know what they're doing. But some guy with a butane torch in his garage and a real tight grip on his wallet, he's the expert.

BTW- most Autoprop anodes run between $15-$20. Your time and effort must not be worth a whole lot to you.

https://www.boatzincs.com/autoprop.html

O ye of little faith! It must be awful cruising with a boat, when you have so little confidence in your own abilities. BTW, if I could get an Autoprop anode for $15-$20, I might not bother, but here, they're about £40. Yes £ not $.


Yes, the manufacturers of zinc anodes will try to blind you with science about the spec of their zinc, but think for a minute what it is and what it is that you want it to do. It has to be eroded in preference to the metal that you want to protect - that's all. In order to do that, it has to be less noble - that's all. The anodes that I have been making for the past dozen years or so have eroded, and my prop and shaft haven't. QED.

[fstbttms]

Well it's your dime, but I sure as hell wouldn't trust my $4000 prop to some shade tree metallurgy.

https://www.boatzincs.com/use_milspec_a18001k.html

[NormanS]

Originally Posted by a64pilot

Unfortunately I don’t believe it’s made anymore, but Islers Diving used to manufacture an adapter for the Autoprop that attached to the same three screw holes like the Autoprop Anode but allowed the use of a standard “B” prop anode.
I’m sure someone could take a prop nut and drill three holes in it and use that.
Some of the best money I spent as the Autoprop anode is a bad joke.

That's interesting. Here in Scotland someone was doing the same. Or he was three years ago, don't know if he's still doing it.

[betwys1]

Originally Posted by Jono as 2234

Thanks for all the responses, I'll give away the idea. Seems too much trouble, dirty, dangerous, possibly ineffectual and bad manners.
Removing the anodes, polishing them back to solid metal would work, however I only slip annually and would not trust the remaining zinc for another year.
I already cast aluminium, so there's an idea. I just scavenge old window frames etc, however the end result is often a little honeycombed. May be an advantage as it increases the surface area.
Or maybe I just spend the $100 like always - teardrop, rudder halves and bow thruster.
Jon

This is a reasonable source for ingots 3.8 lb., $14
https://www.rotometals.com/mil-a-180...ficial-anodes/ mil spec

Outdoors - as welders of galvanized iron soon find: inhaling zinc fumes induces a strong headache.

[sailingharry]

Just to reiterate A64's comments on AL. If you live in brackish waters (for me, the Chesapeake Bay), zinc is an awful material. I still have the last zinc I installed, kept as a Show and Tell. After 3 years (I haul every 2-3 years), the zinc was encrusted with a thick white oxide layer, making it ineffective. I now use AL anodes, and they waste away in a very productive manner. I haven't been able to find an AL "guppy" to hang off the side, but I make one from an AL "Diver's Dream" plate anode, and while the surface is a slimy gross mess (in addition to biologic stuff), it bubbles away in a year or two in a very satisfying manner. Around here, the zinc ones "last forever" (and that's stated as if it were a positive thing.....).


I get so annoyed when I walk around the boatyard and see crusty zincs on the bottom of boats, and the yard installing new zinc anodes. I get even more annoyed when the local chandleries stock a limited selection of AL anodes, making me have to order online. Getting one for a Max Prop is hard, getting a pencil anode for an engine is, as far as I can tell, impossible.



It's not like this stuff is secret. Martyr, Camp, Practical Sailor, etc all clearly state the appropriate material.

[rslifkin]

Originally Posted by sailingharry

I haven't been able to find an AL "guppy" to hang off the side, but I make one from an AL "Diver's Dream" plate anode, and while the surface is a slimy gross mess (in addition to biologic stuff), it bubbles away in a year or two in a very satisfying manner. Around here, the zinc ones "last forever" (and that's stated as if it were a positive thing.....)

I know Defender carries the hanging fish type in Zinc, Aluminum, and Magnesium. Not sure where else you can get an aluminum one though.