Carbon Dioxide as Shield Gas for Brazing

mattmia2

Is carbon dioxide effective as a shield gas to trickle in to refrigeration tubing while brazing? I can can justify buying a co2 tank and different regulator setups for carbonating and for leak testing and brazing but I can't quite justify a co2 and nitrogen setup for the different occasional uses.

Is my assumption that 99.90% pure beverage grade co2 has to be inherently dry correct?

EBEBRATT-Ed

I have been through this before. Most will say "no, dry nitrogen only" because that's what the books say.

I have used Co2 for years with no issue. The tanks are a lot lighter to lug around and they hold way more gas than nitrogen. Go for it and don't look back.

Now, I'll wait for the backlash LOL

Larry Weingarten

Hi, Sometimes the right answer to a question is another question. So, my question: How about making a braze joint while purging with carbon dioxide, then cut the pipe open and see if any scale has formed? I'd be concerned about the 02 part of the gas affecting copper, but that's just a wild hypothetical guess.

Yours, Larry

pecmsg

Just use N2

EBEBRATT-Ed

I have done some braze test joints while purging with Co2. It's not an issue. It's a lot cheaper and you get way more purging gas out of a bottle.

If you want to stay with nitrogen it's fine with me

ratio

A better question would be "Does CO₂ decompose when passed across copper heated to a red hot temperature." I don't know for sure (my public school education ended last century!), but I wouldn't be a bit surprised if it does.

We always just use N₂. Around here, an 80 CU FT bottle is like 12 bucks to exchange after you buy the first one.

EBEBRATT-Ed

Look on U tube "NathansHVAC Co2 brazing" he brazes tubing with and without Co2. See for yourself