I know this is off topic, but I figured someone might be familiar with this. Is it SAFE to solder thin gauge galvanized sheetmetal? I know if you weld galvanized it gives off poisonous fumes but soldering is done at a lower temp. I would be soldering with a propane torch and I would quit applying heat as soon as the solder melted.
Thanks,
Max

I would recomend grinding the galvanizing off at least a 1" back from where you plan to solder, on both sides of the metal. I've never tried soldering it, but I'd think a propane torch would get it hot enough for the nasties to come off.

Galvanized steel is steel coated with zinc. You can't solder to zinc. So removal of the zinc is the first step. Often folks will rid the steel of zinc by using acid. Hit it with acid, clean off the residue and then solder. That leaves an area of steel without solder and without zinc - which can rust.

You shouldn't have any trouble, but do use common sense and good ventillation.

If you follow the procedure listed above, go to a welding supply store and buy an aerosol can of spray zinc to protect the area where you removed the original galvanizing.

My dad was a welding instructor...so I know a little of what I speak. When zinc burns it creates a gas--a poison gas. Zinc poisoning is called the "zinc chills" because you shiver and shake for days afterward. Just be sure you use very good ventilation, like outside in a breeze.

the chef

Back in my youth, I worked part in a construction company shop. Seems to me, the welders there always drank milk, while they were welding galvanized metal. I gather it related to the fumes given off. Explanation?
Grizz

A blacksmith died recently after welding a lot of galvanized pipe .But welding produces enough heat to melt and vaporize the zinc.Molten zinc is very volatile and the fumes are toxic.Think of this when you want to make something out of old cases and melt them !....The zinc paint ,IIRC 97% zinc, will be the equivalent to galvinizing if applied according to instructions.

I experimented with this. Because zinc is a contaminant in our alloys, I figured solder would adhere to it. It did. I used a propane torch and sweat soldered it. When the flux ran and the solder melted I quit applying heat. Afterwards I was able to seperate the metal parts but it took some effort. I'm just wondering if this is a common practice among, say, sheetmetal workers, and is it safe because the zinc never burns.
Thanks for all the replys.

Unless you need a waterproof joint, I'd just pop rivet the sheeting together. Heck, JB weld will provide waterproofing if necessary.

No worry about nasty fumes, likely faster, and plenty strong.

Galvanized with also give you a hammering headache, one so bad you'll never forget it.

FWIW, I've been doing more research. Soldering galvanized is a routine operation. It just needs to be cleaned first. I found information about this in some Sheetmetal Union workers training materials.

As a former sheetmetal worker I can tell you Max is correct. If you are useing soldering irons use muriatic acid as a flux and use 50/50 solder (50% lead, 50% tin). If you are just useing a torch (takes a little more skill to do a presentable job) use 60/40 acid core solder. In either case when you are done be sure to wash the acid off. Good Luck

Yes, galvanized solders just fine with an iron. Use a big, heavy copper iron and acid flux. It is touchy with a propane torch.