Does exhaust pipe tubing have any protective coating?

[Fallon]

OP here- Thanks, guys.

I thought it might be easy and cheap to buy tubing for this at any local muffler shop. (This project is just a whimsical experiment.) Since asking for your opinions, I found a major distributor of exhaust system components online that describes their tubing as aluminized. (Aluminum coated) Direct food contact with aluminum is controversial. Also wondering if "aluminized" is conflated with "galvanized", which is actually, a zinc coating. I heard that welders avoid galvanized steel for health reasons and doubt if galvanize would be used on such a commonly welded product.

Stainless tubing is almost perfect but probably only available from online suppliers. No matter how small the quantity, most of my online orders for steel end up at over $50. I just spent 20 minutes trying to get a shipping estimate for SS tubing online that required my zip code but wouldn't allow me to enter it in their little box. Much to be liked about brick and mortar.

Aluminum, magnesium, & zinc provide galvanic protection for steel. They get eroded before the steel. Galvanic Reaction: Incompatible Metals Responsible for Corrosion has a chart showing which materials are on what end if the galvanic spectrum.

Zinc has a boiling point of 1670f, aluminum boils at 4478f. The melting point for zinc is a bit lower than aluminum as well & a fair bit under the boiling point. So in a hot car exhaust, the higher melting point of aluminum will make it less likely to melt/burn off while still providing galvanic protection. The fact zinc boils so low combined with its toxic fumes makes it hard to weld & a bad idea to weld (without good air purification).

 

[crazyal]

I recently bought some 4" exhaust pipe for some woodworking equipment. 4" works great with flexible vinyl dust pipe. The stuff I bought was aluminized and it welded just fine. I have welded galvanized on rare occasion and this was nothing like that. No smoke or fumes like galvanized. I don't know if I would use it if this is going to be in contact with food.

 

[3Ts]

As for zinc, check out "metal fume fever". Aluminized steel is a steel core with an alloy of aluminum and silicon coating (for type 1 which is probably what you'll see most often).

Aluminized steel - Wikipedia

 

[s219]

Correct, it is aluminized most likely.

 

[dragoneggs]

Let's remember OP is talking food grade and wanting to cook (hot) with it. Cast aluminum I wouldn't have an issue with but Al plated... I would be leery. What really is the plating? Zinc? As I already mentioned, stick with stainless steel if you want to do it right and erring on the safe side.

 

[user.69169]

Galvalume is 55% zink, 43% aluminum + silicon.

Probably won't hurt you considerin people take Zinc pills and probably intake aluminum from pots & pans.

Give some thought to DWV weight copper tubing, readily available as cutoffs from a plumbing shop up to 4".
Of course you cookin acidic items copper can be a problem.

 

[BrokenTrack]

One of the projects our welding students have to do is build a Rocket Stove out of tubing...

This does a lot of things, as they must do shop drawings of the stove including weld symbols in the right places, and do the math on the plans. Then they must program some of the parts into the CNC Plasma Table, then cut, weld the parts together. Some of the parts are cut and bent via the Pipe Fitting Program, Finally they take it up to the Culinary Program, and have those kids cook with their stove. When they are done, the rocket stove is theirs to keep.

This does so much as it collaborates many trades, because welding in the real world involves working with many trades.

Weld Math Class
Welding Program
Pipe Fitting Program
Culinary Program

We use mild steel tubing because we cannot weld anything with hexavalent chromium in it due to the cancer causing effects of it. That includes not being able to weld aluminum or copper-nickel for other health reasons.

Incidentally, my church sponsors a rocket stove program as a missionary service, going to 3rd world nations where fuel is limited, and yet fire is how these poor people cook. We build them rocket stoves in their huts for cooking and heat. Over the years we have sponsored thousands of these rocket stoves....

 

[Ford850]

Back to the original purpose... a cooking widget. Stainless exhaust pipe does seem like the solution. Did you call your local muffler shops? Any custom car or truck shops close by, or maybe a race shop? One of those might have a small piece for a widget. Summit and Jegs list various sizes, and so does Napa.

 

[TractorGuy]

You're gonna need Titanium tubing to be safe.

Hidden Dangers | The Conscious Cook

 

[jmc]

...Stainless exhaust pipe does seem like the solution. Did you call your local muffler shops? Any custom car or truck shops close by, or maybe a race shop? One of those might have a small piece for a widget. Summit and Jegs list various sizes, and so does Napa.

OP here.

I'll call the locals. I need 1 5/8" OD SS w/.065 wall which is common online but probably a long shot locally. Summit was the place that wanted my zip code but wouldn't allow me to enter it. I'll try those other two.

No speed shops around here that I know of or that have a website.

Thanks.