Soldering / Brazing copper to stainless steel keg

[WCG]

Hi guys, have a pony keg and going the route of a 1500 watt hot water tank heater element. Picked up the element yesterday at Lowes (I am in Canada) along with a copper adapter that will work with the threads on the heating element.

To solder the copper adapter to stainless keg was curious what type of solder and flux I should buy. While I was in Lowes I snapped pictures of the different solder and fluxes they had in the plumbing section.

What they had was
1.) Rosin Core Solder - Lead Free - (Electrical)
2.) Acid Core Solder - Lead Free - (General Metal)
3.) Solid Wire Solder - Lead Free (Plumbing)
4.) Tinning Flux (for joining dissembler metals)
5.) Paste Flux (general purpose)
6.) Water Soluble Flux - (Plumbing)

Curious which would be the recommended solder and flux I should buy?

(Will need to post the pictures later, for some reason not able to get them off my phone and onto computer right now.)

Regards,
WCG

[Braz]

To solder copper to stainless you need silver solder and a compatible flux. And lots of heat - mapp gas at least, oxy/fuel is better. I'd find a welding supply place and tell them what you want to attach to what (copper to stainless) and they can recommend the right stuff. Be prepared to drop $30 or so for about 5 sticks of silver solder and flux.

I don't think anything on your list will work long term.

[RyanP]

We silver soldered copper to ss this weekend with no flux and it worked. Mapp gas was used. Had to get teh copper reallly hot.

[myles]

We silver soldered copper to ss this weekend with no flux and it worked. Mapp gas was used. Had to get teh copper reallly hot.

I really wouldn't recomend this practice.

If it worked for you fine, but are you sure? Chromium oxides are a real problem without the correct flux.

If you are soldering copper to stainless you need to be aware of two more aspects. "Crevice corrosion" and "weld decay". Be a shame to waste a good keg through poor technique.

[WCG]

Thanks for the comments back, (parallel I am trying to find a bolt on adapter kit as this is my second option) but going to stop by a local fabricator shop in next couple days to see if they can weld the copper coupling onto the stainless steel keg.

Sure they will have the expertise, but just so I am knowledge when I stop in, if I ask to have it TIG welded is there any cautions I should make sure on. Not familar with TIG welding but if they need to use a filler rod to weld with is there a kind I should request.

[Barney Fife]

You can also have a welding shop braze the copper to the SS if you don't have oxy/acetylene at home. Or find a 1" SS threaded adapter and have that welded to the keg instead of the copper one. In the least, get the right solder and flux; try asking, as suggested, at a welding shop or supplier.

[WalkingWolf]

I'm gonna throw my $0.02 in as a voice for the NOVICE. I have struggled with this, at times mightly, and let it get the best of me. Came back to it and battled on. A month or so ago bgrizzle and I were PM about this very topic and one of the things he mentioned really stuck. Keep the heat away from the SS. Since then I have done two different solderings of copper to SS and both have turned out very well IMHO.

Handheld MAPP torch
Harris Stay-Clean liquid solder
Standard lead-free solder

You will need to rough up the SS. Not just "kind of pass it over" but really sit there and work it to get rid of the shiny top layer. You want the SS to have a brushed look. I then took the piece and cleaned it well with rubbing alcohol. From this point onward I do not touch the metal with my bare hands. I start heating the SS slowly with the flame about 3 inches from the metal. I use a flux applicator brush and when the flux brushed on the SS starts to sizzle I remove the heat and brush on a good coating of flux. Do this in a well ventilated area as this will give off significant fumes. Let the metal cool and the flux dry some-what and slowly start heating the metal again and when flux dabbed on the metal sizzles remove the heat. Apply another good coating of flux. The copper should be fully prepared as well -- I'm not going to get into that as one should have that part down pat. Apply flux to the copper. Apply to all surfaces that will come in contact with solder. In the case of putting a SS ferrule in copper tubing I fluxed both the inside and outside of copper tubing. This next bit is a tip I picked up reading a post by OD. Make a ring with solder that will go around the joint that you will solder. You want the ends of the solder ring to touch but at the same time you want the ring tight to the work piece. Now start heating the copper an inch or so up from the joint. The heat will make its way down and eventually melt the solder. Solder will travel to heat and as the solder melts it is sucked up the inside of the tubing forming a solid joint. Some skills are easier to pick up than others and for me, this was not the easiest one.

good luck

[WCG]

Hi guys, thanks for the insight!

Thinking for this time around and to get up and running quickly, going to have a welder TIG weld S.S fittings to the keg, just placed order last night for some S.S 1" locknuts and S.S 1" half couplpers.

Parallel going to get the torch out and practice soldering S.S and copper on some scrap pieces I have around the farm per WalkingWolf instructions and tips.

Regards,
WCG

[bgrizzle]

WW, those are some good looking solderings there... I think you got it man! Like you mentioned, the trick is to keep the flame away from the area you are soldering or it will burn the liquid flux.

I know i used a pipe wrench to tighten my heating element, and it didnt come close to breaking...

Liquid Flux
Mapp Gas
Lead Free Plumbers Solder

Good Luck

[WalkingWolf]

Harris Stay-Clean liquid solder

I just noticed this error -- this should say flux and not solder.

[BCplumber]

Thanks WW! I just successfully brazed copper fittings onto a ss keg. I did a 3/4 copper FA onto top of keg for a fill valve with a ss threaded plug and a 1/2 copper MA as a drain port with a lead free ball valve. It worked awesome!

I used Harris flux and Harris StaySilv 45 cadmium free

I drilled the holes, sanded the fittings and keg, fluxed it up and then added heat from a oxy/acet torch. I heated the fitting first, then focused on the surrounding stainless being careful not to overheat. The StaySilv is a thin wire and gets eaten up pretty fast, but it worked. I owe it all to you.

[johnhopper1957]

Thanks for the comments back, (parallel I am trying to find a bolt on adapter kit as this is my second option) but going to stop by a local fabricator shop in next couple days to see if they can weld the copper coupling onto the stainless steel keg.

Sure they will have the expertise, but just so I am knowledge when I stop in, if I ask to have it TIG welded is there any cautions I should make sure on. Not familar with TIG welding but if they need to use a filler rod to weld with is there a kind I should request.

TIG is your best option they can fuse it or use filler I use 316L, if it is fused it is neater but harder to do.

[demetroy]

can you do this with oxy/lpg as this is what ill be soldering with

[NcHooch]

can you do this with oxy/lpg as this is what ill be soldering with

Ya, that should be plenty hot for soldering

[demetroy]

can you do this with oxy/lpg as this is what ill be soldering with

Ya, that should be plenty hot for soldering

sweet i was worried about the stainless being that its a harder metal have 3 joins to do as im going to do a continues setup for stripping runs and tri-clamped on and just taken off when doing product

[brewmaster2014]

Hey where did you guys get the Harris product,I'm trying to find store in Montreal that carry it but so far only on line.

[Thirstylildesertrat]

I just carefully pounded the ferrule into the end of my 2" column... Damn dear air tight as is... Then I used a MAPP gas torch to solder on the inside, just for a good seal. I just used regular lead free plumbers solder and water soluble flux... Seems good so far... No leaks as of yet

[clanbree]

Has anyone tried this product for soldering to stainless?
http://airgas.com/product/Welding-Produ ... o_s=gplaus" onclick="window.open(this.href);return false;" rel="nofollow

[clanbree]

Hey where did you guys get the Harris product,I'm trying to find store in Montreal that carry it but so far only on line.

Amazon.com has quite the selection, locally you might call on welding supply firms.

[WalkingWolf]

Hey where did you guys get the Harris product,I'm trying to find store in Montreal that carry it but so far only on line.

Amazon.com has quite the selection, locally you might call on welding supply firms.

I searched high and low locally and ended up ordering it online.

At almost 4 years now the connections have held up well and look today as the pictures above. Best of luck with it.

[cranky]

Bellybuster has a good tutorial on this including a video here
http://ww.homedistiller.org/forum/viewtopic.php?t=36347" onclick="window.open(this.href);return false;" rel="nofollow
He used ss to ss but Pyewacket has a tutorial on copper to ss
http://homedistiller.org/forum/viewtopi ... =2&t=39820
I actually tried both using only a propane plumbers torch and was quite successful. Corene1 did tests on the strength of soldered joints and found them quite acceptable. I found that copper to ss was actually much easier than ss to ss but neither was a problem. Like WalkingWolf said prepping is the most important part.

[NcHooch]

when I'm workin on unusually difficult joints, it helps a lot to tin the surfaces (proper flux and silver solder) first before trying to join 'em

[slowswim]

I am having a hard time soldering my stainless steel ferrule into my 2" copper pipe.

I originally tried to use the water soluble paste flux. That didn't work at all so I went to a local welding supply store and bought a special flux they recommended. See below. It says for "brazing" but they assured me it would work for soldering.

I've cleaned the ferrule and the copper with simple green then rubbing alcohol. I've scuffed up the stainless steel a good bit with 60 grit sand paper. I've even tried to heat the SS ferule by itself to try and get the solder to stick to it first with little to no success. I got a few very small droplets of solder to stick but otherwise it's just not working.

Can anyone give me any additional insight on what might be wrong? Thank you!

[still_stirrin]

I am having a hard time soldering my stainless steel ferrule into my 2" copper pipe.

I originally tried to use the water soluble paste flux. That didn't work at all so I went to a local welding supply store and bought a special flux they recommended. See below. It says for "brazing" but they assured me it would work for soldering.

I've cleaned the ferrule and the copper with simple green then rubbing alcohol. I've scuffed up the stainless steel a good bit with 60 grit sand paper. I've even tried to heat the SS ferule by itself to try and get the solder to stick to it first with little to no success. I got a few very small droplets of solder to stick but otherwise it's just not working.

Can anyone give me any additional insight on what might be wrong? Thank you!

Here's a link to some suggested methods to use on your construction:
http://homedistiller.org/forum/viewtopi ... g#p7291487

The "construction" forum has several threads that discuss this.
ss

[slowswim]

Thanks, SS

I hadn't come across that link, thank you. I guess it's now the solder i'm using?

I don't have the MSDS sheet but will inquire.

[cranky]

I'm guessing it's because your trying to use acid core solder. you are already using flux so you need solid core solder not acid core. I'm thinking the acid is causing the problem.

[just sayin]

I have had good luck joining copper to stainless with Harris Stay Clean liquid flux on well prepared stainless, using an antique heavy copper electric soldering iron and a silver bearing lead free soft solder to tin or wet the stainless. Then just flow standard lead free solder between the copper and tinned stainless being careful to direct heat to the copper.
Note: silver bearing is stronger standard lead free solder.

[humbledore]

Well I am not an expert. But silver solder melts at, what, 400-500F? And your brazing flux here is not "chemically active" below 800F. Might be a problem. Just sayin is right, try Harris stay clean flux. And solid core silver solder, like Harris stay brite8. I've also used Oatey brand solder.

[Hound Dog]

Yep, you are just struggling with the wrong stuff. Use Harris Stay Clean flux and Harris Stay Brite solder. Sand everything up and douse it good with flux. Wrap a ring of solder around the joint and set the torch as low as you can. Heat away from the joint very slowly. When it starts to get hot drip a bit more flux in the joint. DON'T breath the fumes. Keep heating slow and patient. If it browns, be prepared to rinse a bit more flux in it. Then the solder will just take, boom! You got it. If you have gaps to fill you can bridge them afterwards with regular solder. It's easy if you use lots of flux.

[slowswim]

Thanks to everyone. The 3rd time around did fantastic.

I bought some better solder (Oatey - no acid core) and used the Harris flux (pictured above), cleaned everything up real pretty and then slowly heated the copper up with the ferrule inside. The joint seems pretty solid.. worlds better than my previous attempts. If anything, I at least know now I've got the right combination of flux and solder.

I find all of the nuances of pulling stuff like this off pretty fun and an incredible learning experience. It also makes it that much more fun to share in the journey. Thanks again guys.

Cheers,

SS