Thread: Working with galvanized metal

Hi all, first post here. I'll do an intro a bit later, if all goes well.


I'm currently about to undertake building a used oil heater.
I've seen a number of ideas on videos.
This will be a multi fuel heater burning both oil or wood.


The videos I have seen mostly use a 25 gal propane tank, of which I have one at my disposal.
For me the tank is a little too small to double as a wood burner, so I'm looking at a bigger tank that I own.


It is an older water, maybe pressure tank. I haven't been inside it yet, but the outside is clearly galvanized.
I'm quite aware of the dangers in welding galvanized metals.


I guess my first question would be one looking at how long heated galvanized metal gasses off.
If I were to get this thing real hot (outdoors) would it reach a point after X amount of time that it would then be safe to clean up and weld on, or does galvanization continue to gas off indefinitely?


Am I being stupid to even try such a build with this tank?


I will greatly appreciate any feedback.


Thank you,


Joe

Galvanising is dipping a steel object in molten zinc, so theoretically if you raise the temperature of the object over the melting point of zinc it should melt off. In practice I'd suggest that it comes down to an uncertainty as to whether all the zinc is off - for example there will be seams where the zinc has wicked in.
Personally I would be continuing the search. Perhaps a length of steel pipe and cap the ends as necessary?

Michael

Originally Posted by Michael G

Galvanising is dipping a steel object in molten zinc, so theoretically if you raise the temperature of the object over the melting point of zinc it should melt off. In practice I'd suggest that it comes down to an uncertainty as to whether all the zinc is off - for example there will be seams where the zinc has wicked in.
Personally I would be continuing the search. Perhaps a length of steel pipe and cap the ends as necessary?

Michael

Thank you Michael.

I'm trying to keep this project mostly to what's on hand.
If I can't determine whether or not galvanized eventually quits gassing off, or being dangerous, then I'll end up resorting to the propane tank.


Joe

My gas forge is made from a 5 gallon Galvanised steel propane tank. After cleaning it out inside I cut the ends off with an angle grinder. I reused the ends as doors and welded steel seals.rims, door closures and hinges on both doors.
I took no special precautions when I used an angle grinder to roughly grind the Zn from the weld lines with a flap sander.
The welding was done under a fume hood and there was still some Zn fumes but they all went up the fume hood.

After the welding there was plenty of Zn left on the tanks.
I painted the forge with pot belly black and over successive firings, around the doorways where the forge gets hottest the paint and Zn underneath has all burnt off.
I did the first few firings outside and could stuff coming off the forge for about 10-15 minutes after it got up to temperature.
After about the 3rd firing there was little left to burn off.
I now run the forge inside my shop but I do have two ventilation fans running with a total of 2500 CFM of ventilation, not for the Zn, but to vent the CO/CO2/heat which it produces in fair quantities.

If you were to run your burner outside I would see no problem. The heat from the firing will make the fumes rise rapidly and disperse the Zn.
Zinc oxide fumes won't actually kill you but will seriously take your breath away if the concentration is high enough - I have experienced that a few times.
The real danger is prolonged exposure (many days) to Zn fumes, which leaves lungs weakened and susceptible to other diseases which is what kills you.
Humans are already constantly exposed to small concentrations of ZnO dust, ZnO is found in rock duct and is generated from the large numbers of galvanised roofs and other objects that are slowly degrading.

Light it up outside(away from people) and heat it up a lot hotter than you will ever need it, when it stops smoking the Zn should be gone forever. Then repair any damage and paint it if so desired

Thanks for all the input folks. I think I'm going to go ahead with the build, and see how it burns off. If I don't feel that it's safe, it will be an nice addition to my yard art.
For anyone interested, this video is my inspiration for the project.

The one thing that is missing is a water jacket to feed radiators and get the heat out to where it may be more useful.

Originally Posted by BaronJ

The one thing that is missing is a water jacket to feed radiators and get the heat out to where it may be more useful.

What I'm seeing in the video is just a start to possibly further additions.
I wish I would have had the forethought to plumb in my concrete floor for circulating water heat. Too late.

But most likely I will incorporate some sort of water heating coil, to accomplish any number of tasks.
One fantasy would be to create a steam powered electrical generator to supplement my solar/battery bank.
Instant hot water would come in handy for a number of purposes, though I seriously doubt I'll re-plumb the place, although adding a radiator would help disperse more heat, and make extra use of the BTU's that would otherwise waste out the chimney.

We live completely off grid, and are always looking innovative ways to get things accomplished.

Since you don't need zinc on a furnace, why not just dissolve it off with cheap Hydrochloric Acid (muriatic acit / spirits of salt)? Doesn take long at all. Do it ouside, because it gives off lots of hydrogen and irritating and corrosive fumes. If you collect the liquid that results, you can bottle it and use it as soldering flux.
You would need a flat tray that you can lie the tank in and just rotate it a bit every time the hydrochloric stops bubbling. When it stops bubbling with a new zinc surface, its 'killed'. That's what Bakers Soldering Fluid is. You will then have to replace the acid and keep turning the tank. At the end stand it on end in the tub - both ends. No more zinc.....

Originally Posted by jhovel

Since you don't need zinc on a furnace, why not just dissolve it off with cheap Hydrochloric Acid (muriatic acit / spirits of salt)? Doesn take long at all. Do it ouside, because it gives off lots of hydrogen and irritating and corrosive fumes. If you collect the liquid that results, you can bottle it and use it as soldering flux.
You would need a flat tray that you can lie the tank in and just rotate it a bit every time the hydrochloric stops bubbling. When it stops bubbling with a new zinc surface, its 'killed'. That's what Bakers Soldering Fluid is. You will then have to replace the acid and keep turning the tank. At the end stand it on end in the tub - both ends. No more zinc.....

The muriatic acid from home depot averages about 5-6 bucks a gallon.
Off hand, I'm not sure if I have a tray or whatever to set the tank in, but kick the tires on this: What if I apply the acid using my power washer?

Originally Posted by bbqjoe

The muriatic acid from home depot averages about 5-6 bucks a gallon.
Off hand, I'm not sure if I have a tray or whatever to set the tank in, but kick the tires on this: What if I apply the acid using my power washer?

One very nackered power washer...

Originally Posted by BaronJ

One very nackered power washer...

This is far worse than breathing the ZnO fumes.
You will destroy your clothes, burn your skin and gas yourself

Originally Posted by BobL

This is far worse than breathing the ZnO fumes.
You will destroy your clothes, burn your skin and gas yourself

I agree! DON'T spray the stuff EVER. Letting it sit in a tub is bad enough. the last thing you want to do is splash it about!

Although, brick cleaners sometimes do spray hcl, with a low pressure sprayer. I'd think a plastic lined tub of some sort would be better.

-russ

Surely you can find an old bath tub some where, at a tip maybe?
Kryn