Who's afraid of Galvanized Pipe anyways

[rectifier]

I read a recent post which mentioned galvanized pipe and toxicity and realized this is a persistent myth in stove circles. I have a background as a chemist, my work includes machining and fabricating, and I think I know enough about galvanized to ease some fears and help dispel the myth.

First, galvanized does not give off 'cyanide fumes'. It DOES give off zinc oxide fumes, which can cause metal fume fever. Metal fume fever is an immune-response condition that goes away in a day or two as your body absorbs the zinc. It's rotten, much like the flu, but it is rarely fatal, usually only when the exposure is extreme and the person has a pre-existing lung condition. It happens to welders all the time, almost considered to be a standard occupational hazard. Welders who work in a enclosed environment and don't wear protection develop resistance rapidly.

Second, galvanized steel rarely gets hot enough to create said fumes except under conditions of welding, grinding or casting. During a stove test, I managed to oxidize 4' of my galvanized flue (it was under a fume hood, just in case). White oxides formed on the pipe but none was released into the air as fume. The fume is extremely visible when welding on galvanized material, as thick white smoke.

Zinc boils at 907C, ZnO at 2360C, and rapid oxidation occurs at much lower temperatures near the melting point of zinc (420C). Once the zinc has been converted to oxide, it is safe. Your stove will never reach 2360C without forced air or oxy mix. I personally use a fully oxidized white zinc-coated elbow as part of a stove I operate indoors, and it is completely inert. I have never experienced metal fume fever myself as I always am sure to have good ventilation and a respirator if I weld galvanized material.

I think galvanized is actually a better material for heat risers if you wish to use thin steel. The layer of zinc oxide will help protect the steel from oxygen and heat damage, I always use galvanized for heat risers in my small stoves and it seems to hold up very well. I always fire them gently at first to oxidize the zinc rather than melt it into a pool at the bottom of the riser. Any oxide fumes will find their way out the flue and not into anyone's lungs.

Finally, galvanized steel is commonly used, within code, as an exhaust duct for gas appliances (go look at your hot water tank or furnace) and even to BUILD WOOD STOVES!
Ex. www.rileystove.com/products/stoves/riley/flap-jack.html is constructed with 18ga galvanized steel! No Riley customers have died yet!

Of course I'm open to any anecdotes of people who have gotten sick from galvanized stovepipe, so feel free to let me know if you or anyone you know has gotten sick.

[pinhead]

As a farm kid with plenty of welding experience, I can attest to the accuracy of this post.

I didn't realize that it had to get that hot, though, to create the vapor; I generally keep my nose away from the oxidizing pipe until it turns white and then after that don't worry about it. It's good to know that I've been overly cautious.

[canyon]

I've gotten sick but it was from hours of welding galvanized ducting for a commercial hood. I now know better and avoid it or if I have to work with it I use my "breathe cool" positive pressure ventilation system. Thanks for sharing the info, certainly eases the worries some. I still don't like the smell and will continue to avoid it for hot exposed use but maybe I can slack my guidelines for mass bench burial. Up until now, I have preburned (and recomended in workshops taught) any galvy parts in a burn barrel outside with a breeze to keep on the upwind side for breathing. Would be nice to skip that step.

[rectifier]

Well, I would say a much more dangerous gas can leak inside a bench when the pipe degrades (monoxide) and if the bench is built well enough to contain potential monoxide leaks, you don't have to worry about relatively heavy and condensing zinc oxide fume. I doubt it would make it more than an inch inside even a loosely built bench before it condensed on the cool and rough surfaces inside, becoming inert zinc oxide.

[satamax]

Rectifier, one question.

I made a barbecue grid long time ago, out of a shoping troley bottom. I brushed it with hydrochloric acid, and burned it for a long time to get rid of the zinc. I now have to clean another one, the old one being dead, ish. What would you recomend?

Thanks.

Max.

[rectifier]

Shopping trolleys are usually chromed, not galvanized. Chromium is relatively inert (it's often plated on to food contact surfaces including cheap BBQ grills) but chromates (especially hexavalent chromates) are much more toxic than zinc. I would not recommend putting acid on, or burning at high temperature, the shopping trolley.

For that matter, I wouldn't recommend eating anything off of metal of unknown composition!
Hate to say it, but your safest bet for a big BBQ is going to a metal dealer and buying a good sized chunk of steel (or stainless) grid from the offcuts bin. Often offcuts are sold by the pound and come out really cheap.

[panbreaux]

i've torch cut and welded galvanized steel for years and never had more than a bit of irritation when in an enclosed space while doing it. i'd say it's about the same level as choking on wet smoke when trying to blow a fire into flames. i've seen many people use galvanized catwalk for pot stands over a campfire and can't say i've ever seen the galvanizing smoke up like it does with torches or welding. with repeated use over a fire it does start to peel off, but i think that's more of the steel and zinc doing different things at different temperatures.

i'm thinking of using a salvaged galvanized water tank instead of a 55 gallon barrel over my 4" steel rocket, figuring it would last longer than the barrel and i could shorten my feed tunnel more due to a smaller outside diameter of the water tank. currently with the tunnel being 12" long, the heat concentrates in the feed tube instead of the 36" riser. my main concern is the tank being too dense for my 4" rocket to heat and burn everything efficiently. i've only calculated the top gap which is 1", but haven't calculated the side gaps since i lack the inside diameter of the water well tank and any needed compensation for the denser wall thickness.

[morticcio]

If you use galvanized pipe for the bench is it be advisable to "burn" it off first or is it okay to use as is?

[canyon]

Anywhere it is exposed to the hot temps, like the first few(4?) feet of the bench or if it is not buried in the bench (cleanout caps, exit flue stack and fittings etc.) I prefer to burn it off first.

[morticcio]

Mar 4, 2012 9:17:05 GMT -8 canyon said:

Anywhere it is exposed to the hot temps, like the first few(4?) feet of the bench or if it is not buried in the bench (cleanout caps, exit flue stack and fittings etc.) I prefer to burn it off first.

Many thanks canyon

[rob]

Is it ok to use galvanized sheet metal as a heat shield above my wood stove "grandpa fisher "in my basement. this is my only source heat for my home "old farm house". from top of stove to sheet metal is 4feet. it gets pretty damb hot. do i need to be worried about gases. It has on been up for a couple days now.

[Deleted]

Nov 24, 2013 7:44:59 GMT -8 rob said:

do i need to be worried about gases.

No.

To get zinc smoking (forming zinc oxide smoke) it has to be heated to its boiling point 907 °C, 1665 °F or above.

periodictable.com/ZincSafety.html

[lightlover]

I used to weld for my grandfather (who's long passed on) he worked in the ship building yards for the navy during WWII. They would drink buttermilk after welding or cutting galvy materials to help overcome the effects of the white smoke/fumes...Part of their work was to coat the ship welds with galvanized rod once done (torch work in those days I believe). He did have some lung damage from the fumes of welding ships in the war effort. God only knows the conditions in those days. Later when I had to weld galvanized material I used an air hose to make a breeze in my work area. If you did breath those fumes you knew it as your throat would get sore and drinking buttermilk would help a little bit. I'm definitely not an expert but in my experience it took welding heat to create those fumes. A quick google shows that oxy torches can easily get to 3100 centigrade and arc welding easily gets above 5000 degree C...well above our stove temps.
Hold your breath...stay safe ;o)

[electricshiver]

Hi so forgive me if this question is redundant because it seems it's been answered here in this thread. But I am thinking of using this double walled galvanized coming out of the side of my barrel on my version of the "rocket mass heater" which is my steal fireplace with the riser going up into a 50 gl drum.

So I'm good with the galvanized out my bell drum correct?





Also. How do I share pictures here?

[ubxmac]

I have used the galvanized duct pipe for gas stoves in my Rocket Stove for years without any issues. I have always, on a new build, just burned the stove 4 or 5 times before use to ensure it works but never had any effects from it. I'm currently building a new and better design now, just waiting on the Rustoleum High Heat Ultra Paint to be delivered so I can make the outside of this Rocket Stove match the color of my Weber Kettle Grill and the High Heat Smoker Gasket to protect the stove top ring and stove body when I disassemble it for cleaning. If anyone would like to see pics of my new Rocket Stove, just tell me/teach me how to add them on here.
-UB