Welding S/S to copper

Ive been lucky enough to find three old 30gallon copper geysers. Besides being very shiny and pretty they're big enough for 20 gallon batches.

Is it possible to weld a stainless steel fitting to a copper jacket ?
Will I need TIG/MIG or will a regular inverter/arc welder work ?
Or is brazing / acetylene a better option ?

I currently use a 10gallon MLT and fly-sparge. Are there any aspects I should consider with regards the manifold or is it just a bigger version of my current one ? If I remember there is a limit to the aspect ratio of the MLT before efficeincy starts to suffer - can someone tell me what this limit is ?

Are there any other considerations for copper or large systems ?

I think you're looking at either brazing with copper filler or silver solder. Welding is more like joining two similar metals at the molecular level.

Go with brass fittings when you are working with copper..I don't think copper can be welded to stainless. You will need to use dialeteric unions when joing copper and stainless.

Is there not lead in brass ?
What is a dialeteric union ?

A dielectric union is used to break the electrical contact between two dissimilar metals to prevent galvanic corrosion. It is essentially a union with a plastic washer inside. You can get them at HD.

There is lead in brass but is in such a small quantity that it isn't much of a concern. You, most likely, have brass fittings and maybe some faucets all through your house that are brass and haven't bothered you yet. If you are still concerned about it... Brass can be pickled to leach out the lead in the surface structure of the brass. It would only be for a few angstroms into the surface but that should be more than sufficient to satisfy your concerns.

If the lead content worries you, you can buy "lead free" brass parts.

Solder it with 56% Silver Solder. SS to Copper will work you just need to be very carefull with the heat!

Special Hops said:

Go with brass fittings when you are working with copper..I don't think copper can be welded to stainless. You will need to use dialeteric unions when joing copper and stainless.

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You don't need dilectric unions for copper or brass to stainless. The two are close enough in the galvanic series that you don't need it. I have several copper to stainless connections (copper plumbing to stainless tri clamp) in my system and have never seen any corrosion.

http://corrosion-doctors.org/Definitions/galvanic-series.htm

Thanks guys.

Why not solder copper fittings to your pots?

i doubt you'd find any welders that could tell you how to weld copper to stainless (i know i can't do it), you could try brazing it, but stainless is a lot more brittle than copper; try JB weld?

The short answer is yes. You can indeed weld SS to copper. As mentioned, the galvanic scale is close enough that there is minimal concern. Use SS wire for the filler or a higher nickel content rod like Inconel 625. It will be tricky to weld the two together due to the heat being sucked away by the copper. You will most likely need to pre-heat the copper so you don't loose so much during the welding process.

I have welded copper to SS using SS filler, Inconel 625, and Silicon bronze.


Edit: I should mention that the process to do the welding is TIG. You will also need to purge the weld area properly. There is no getting around the purge on this one IMO.

Why not solder copper or brass fittings for the manifold or bulkhead?

hah i guess i stand corrected? we had a project one time at work doing baffles inside a chemical tank that was all inconel, and they said we could use 309 rod for fillets, but ive never run into an instance where straight copper was welded at all. we also did copper nickel piping in a yacht's engine room two years ago, but i thought i understood that they used that because copper alone was too maleable to be welded accuratly?

turnNburn said:

hah i guess i stand corrected? we had a project one time at work doing baffles inside a chemical tank that was all inconel, and they said we could use 309 rod for fillets, but ive never run into an instance where straight copper was welded at all. we also did copper nickel piping in a yacht's engine room two years ago, but i thought i understood that they used that because copper alone was too maleable to be welded accuratly?

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Not to get off topic but, Nickel is added to the copper to give it more fatigue strength. You get all the benefits from the copper corrosion resistance and added strength from the nickel.