home made anodes

[drakes drum]

Has anyone had a go at making their own anodes at home. I have a fine collection of old half used anodes plus a strong sense of outrage at the price of new ones. I was thinking of melting down the old anodes since zinc melts at only 420C and recasting them onto the old steel centre plates.

Anybody done it? If so what did you make the moulds of?

 

[Halo]

Look at previous threads on this. Whatever you do make sure that any moulds are bone dry

 

[RichardS]

My plan, which has failed so far - was to take a plaster cast of a new saildrive anode whilst I have one, then make a new positive anode out of the liquid epoxy stuff you can buy, so I can keep the epoxy anode at home and make more plaster casts from it whenever I want to in the future.

The saildrive anodes are quite complicated and the holes etc need to be cast in the right places. Unfortunately, my first attempt at plaster casting has broken apart trying to get the anode out of the plaster because of all the internal contours. Getting the plaster mixture wrong didn't help either.

I have not yet decided whether to try again or give up.

Richard

 

[VicS]

Has anyone had a go at making their own anodes at home. I have a fine collection of old half used anodes plus a strong sense of outrage at the price of new ones. I was thinking of melting down the old anodes since zinc melts at only 420C and recasting them onto the old steel centre plates.

Anybody done it? If so what did you make the moulds of?

The problem of doing that is ensuring that the zinc you recover is not contaminated with iron from the old steel centre plates

the zinc used is to US military spec 18001:- Cu 0.005%, Al 0.1-0.5%, Cd 0.025-0.07%, Fe 0.005% max, Pb 0.006 %max, Others 0.1% max, Zn remainder

Note the very low maximum iron content allowed. Iron contamination will render the anodes ineffective.

Google will find plenty of info on the casting process

 

[AntarcticPilot]

There are issues about impurities in the zinc; I gather that any iron makes the anode ineffective, or even worse, accelerates corrosion elsewhere! So, you need to be absolutely sure the zinc you use is an appropriate grade. Others have suggested that old anodes will have too much iron from the old straps. Vyv Cox has quoted chapter and verse on this many times.

 

[GrahamHR]

Really, does iron diffuse into the zinc alloy anode material at any appreciable rate in the solid state at ambient temperatures ? If so, then it'd render any commercially sourced anode useless. anyhow ! I can imagine if the iron carriers were in the melt it might occur, otherwise I'd be surprised if it happened at all.

 

[NormanS]

I make my own anodes for my Brunton's Autoprop, using zinc from old anodes. I don't experience any problems from so called contamination. It's funny how the steel straps embedded in most anodes don't seem to cause any "contamination". My anodes last just as long as the expensive ones from Brunton's. As long as you skim off anything floating on the molten zinc, and stop pouring before you empty the vessel, you've taken care of any impurities, either lighter or heavier than zinc.

I use a tin can of the appropriate diameter as a mould, and then set to with a hacksaw and a drill. If I was charging for my time, I'd be cheaper buying them, but my time is free, and so is the zinc. Go for it.

 

[GrahamHR]

I make my own anodes for my Brunton's Autoprop, using zinc from old anodes. I don't experience any problems from so called contamination. It's funny how the steel straps embedded in most anodes don't seem to cause any "contamination". My anodes last just as long as the expensive ones from Brunton's. As long as you skim off anything floating on the molten zinc, and stop pouring before you empty the vessel, you've taken care of any impurities, either lighter or heavier than zinc.

I use a tin can of the appropriate diameter as a mould, and then set to with a hacksaw and a drill. If I was charging for my time, I'd be cheaper buying them, but my time is free, and so is the zinc. Go for it.

Referring back to my 5 minute earlier post I also make my own anodes ! ( casting the same way with the same precautions I used when I started casting lead fishing weights 50 years ago !)

 

[VicS]

Really, does iron diffuse into the zinc alloy anode material at any appreciable rate in the solid state at ambient temperatures ? If so, then it'd render any commercially sourced anode useless. anyhow ! I can imagine if the iron carriers were in the melt it might occur, otherwise I'd be surprised if it happened at all.

No body is suggeting that iron difuses into the anode from the strap. Antarctic Pilot and I wers simply pointing out that cantamiation of the zinc by irons must be avaoided .

I really fail to see why any documented fact has to be cahllenged , mis interpretted or mis quoted and turned into an argument for what seems to be purley the sake of starting an argumenent

 

[superheat6k]

I used to cast engine pencil anodes using 22mm copper pipe with a brass stop end for the mould.

I also made a simple crucible to melt the zinc into from two 28mm compression elbows both facing upwards with a short piece of copper between. Mount the crucible in a vice at about 30 degrees, then heat the crucible with a turbo torch then melt the zinc direct from the donor anode into the upper opening. As the zinc melts the pure metal flows to the lower elbow leaving the crud behind. When the lower end is almost full briefly preheat the mould then pour the molten zinc into the mould using a plumbers wrench.

No iron components are involved.

Gloves goggles and overalls with long sleeve are a must.

However, more recently I have found simply buying zinc bar is far simpler. I simply turn them to finished required size and drill and tap a mount thread.

To make anything larger than a pencil anode would be very difficult to get the amount of heat in to produce the molten volume required.

 

[Lon nan Gruagach]

A note about casting.... your model and mould need to be a bit bigger than the desired piece since once it cools it will shrink. so making a mould from a new original isnt going to be just right. Might be close enough, but dont be too surprised if its a bit wee.

 

[NormanS]

A note about casting.... your model and mould need to be a bit bigger than the desired piece since once it cools it will shrink. so making a mould from a new original isnt going to be just right. Might be close enough, but dont be too surprised if its a bit wee.

I really can't see how the amount of shrinkage involved would affect the working of an anode. The ones that I make for my prop are finished by hand after casting anyway.

 

[Lon nan Gruagach]

I really can't see how the amount of shrinkage involved would affect the working of an anode. The ones that I make for my prop are finished by hand after casting anyway.

Depends on the anode, a blob on a steel bar won't matter, but people seem to be discussing some fancy shapes. The first thing that would go wrong is hole spacing.

 

[NormanS]

Depends on the anode, a blob on a steel bar won't matter, but people seem to be discussing some fancy shapes. The first thing that would go wrong is hole spacing.

I drill and counter bore mine after casting. My casting is very basic, and the anode for my prop is quite complex, so after casting, there's a lot of work with a hacksaw. I didn't say it was the most efficient way of getting an anode.

 

[Bongo]

Anyone got dimensions for a 16"Gori prop anode..the little triangular one.? I've roughed one out of an old anode but it's probably too big.

 

[Iliade]

Zinc is fairly innocuous, required even, but do beware of inhaling the fumes from the molten metal: https://en.wikipedia.org/wiki/Metal_fume_fever

So long as you don't melt the iron straps you are unlikely to contaminate the zinc.

 

[MM5AHO]

Iron (and in fact many other metals) will DISSOLVE in liquid zinc. That's where the contamination comes in, and to which has been referred. Its not solid lumps of steel cast into a lump of zinc, but low levels of other metals alloyed in.
For example lead will dissolve up to about 1.5%, Iron to about 3% or more.
Cu, Sn, Mg, Al all dissolve in zinc. These levels of other metals dissolved in the zinc will greatly affect the properties of the zinc when used as an anode.

Metal fume fever from Zinc only happens at elevated temperatures, way above the melting point, nearer the boiling point. Examples are welding zinc coated metals (galvanized steel) when the zinc vapourises.
Zinc melts at 419C, and this sort of activity (making anodes) should be done at between 430 and 460C There's no need to heat the zinc any hotter that just above melting point. If you get fuming, the temp is way to high.

 

[drakes drum]

Any practical tips as to:

1/ what to use as a meting pot
2/ how to heat the pot
3/ what to make the mould out of?

 

[NormanS]

Any practical tips as to:

1/ what to use as a meting pot
2/ how to heat the pot
3/ what to make the mould out of?

I melt mine in an iron ladle, which I used to use for pouring pitch into deck seams.
I use bricks to support, and enclose the ladle, and heat it with a Calor gas blowtorch.
I have, in the past used a wooden mould, lined with purimaceous (fire) cement. It wasn't very successful. Probably a plaster mould would do, but it must be absolutely dry. The ones that I now make for my Autoprop, are conical, so I just use a tin can of the correct diameter, pour in zinc to the required depth, and then when cold, drill, counter bore, and finally shape with hand tools (hacksaw etc).