Working with Galvanized Metal

[samadams_2006]

Hello,

I'm working with some galvanized metal ( the stuff that you use to take the smoke from a wood-burning fireplace out through the roof of a house) that I'm bending into a box... about 16" x 4". It has the right shape, but I want to make sure that it is waterproof as it is going outside, and want to ensure that it will stand the test of time in regards to moisture, heat, cold, etc. What is the best way to ensure this? I've thought that maybe I should purchase a soldering gun and put some solder on the joins...will this stand the test of time? How about epoxy or liquid nails? How about using both solder and some sort of adhesive?

Thanks

[Joe]

You won't find a soldering gun with enough heat to solder galvanized. If you must experiment, buy a propane torch kit with a soldering tip and adapter. You'll need 50/50 lead tin, modified acid liquid flux, other soldering supplies. Your success will likely be limited, so to be practical, take the next big step. Stop by a welding supply store and buy a silver soldering kit. It will have a small roll of silver solder and the proper flux. The propane torch is hot enough to do light gage galvanized. Clamp your project seams with minimal gaps, heat the metal to almost red and apply flux. Heat as needed to let the flux flow, feed in a dab of silver solder to make the joint and allow to cool. Silver solder is like brazing, but takes much lower temperatures. It also works very well on stainless steel, so consider that for your project. Cut off SS sheet pieces can be had at nominal price at any sheet metal shop. The silver solder is pricey, but worth it for what it can do. Enjoy.

Joe

[jmeehan]

If the galvanizing coating is not cracked or compromised, it should be fine. If it is I don't think solder would work well. Some sort of protective coating suitable to direct exposure to the elements and any heat levels it might be exposed to would be the only choice.

[dpb]

samadams [e-mail] wrote: ...

...

How are you planning on mounting the lid (I assume there must be an access of some sort to get the contents into the box)?

If that has to have access, it'll need a good gasket or if access rarely needed it could be caulked w/ a good rtv but will be a pita to get into.

--

[HeyBub]

Soldering is not usually dependable as a mechanical connection. Certainly not for electrical stuff. Even in plumbing a solder joint should not be subject to stress.

I'd go for rivets for the mechanical strength and the appropriate glue to make it waterproof.

[George]

1. Solder pretty much means flux. Flux corrodes. It's surprisingly hard to clean it all off.
2. Long ago, I did some brazing (oxy-acetylene) on galvanized. It did some pretty scary (though apparently short-term) stuff to my lungs. If you use flame for solder/silver solder/whatever, I suggest using serious ventilation.
3. At least with the brazing I did, the heat destroyed the galvanize coating.

G

[Boden]

I use a Racal/3M powered respirator with a long hose. The air inlet and HEPA filter is about 50 ft outside of the boathouse I weld in. My lungs thank me. I used to abuse them, but my one post retirement molecular biology course convinced me that although I got away with doing stupid things when I was young (like breathing bad stuff) I wasn't going to be able to do it now.