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View Full Version : Where to buy flux for brazing steel & cast iron



RWL
09-21-2010, 12:12 AM
Peters Blue Flux has been recommended for brazing steel and Peters Black Flux has been recommended for brazing cast iron, both with bronze rod. Finding a place to buy flux has not been easy. Google wasn't much help, and I didn't find it on Amazon or eBay. There's only one welding supplier left in the area and they don't stock brazing flux. Google puts so many non-relevant links on the first page any more that I even have difficulty finding the manufacturer's web site.

Where can I buy Peter's Blue and Peter's Black fluxes? Alternatively, are there other brands that you like that are more readily available on line?

chipmaker4130
09-21-2010, 12:58 AM
I use one flux for both, and I think it is plain boric acid in powder form (borax).

Bruce Griffing
09-21-2010, 02:59 AM
Borax is a good flux, but please note that borax is not the same thing as boric acid. Borax is a term that refers to several sodium borates - these are sodium salts of boric acid.

lazlo
09-21-2010, 09:54 AM
Anhydrous borax (which is hard to find) is decent flux, but it melts into borosilicate glass, which is a PITA to get off the workpiece.

This was my setup for forge-welding bicycle chain into Poor Man's damascus :)

http://i164.photobucket.com/albums/u15/rtgeorge_album/Blacksmithing/chaindamascusII-1.png

Boric acid is also a decent flux, but neither are a clean as Peterson's.


Where can I buy Peter's Blue and Peter's Black fluxes?

"Peterson" Blue and Black flux. Your local welding supply will carry Peterson's Blue (I buy it at Airgas). I had to order black flux (for brazing carbide) online.

winchman
09-21-2010, 10:20 AM
This place has blue and black paste fluxes, but it's packaged under a different name:

http://www.gasflux.com/paste.html

lynnl
09-21-2010, 10:57 AM
I've never been sure; is this the same Borax that's used as a laundry detergent, or detergent enhancer?

lazlo
09-21-2010, 11:12 AM
I've never been sure; is this the same Borax that's used as a laundry detergent, or detergent enhancer?

20 Mule Team Borax is what I used on the anvil picture above. It's got a lot of water in it, so when it heats up, it boils and froths (and falls off if you flip the piece over to flux the other side). Anhydrous borax has had the water driven off. You can put 20 Mule Team in the oven for 20 minutes and get close to the same thing.

By the way, and old blacksmith's recipe is 9 parts borax and 1 part boric acid (from roach poison). Still, you'll get better results with Peterson's.

Forrest Addy
09-21-2010, 02:12 PM
I've been using 20 mule Team washing soda for 50 years right out of the box.

The box says "sodium borate" on the little panel on the side. I bought a 10 lb box in 1985 or so at the old Safeway. I've used only about half of it. It's all caked up now but when I need to I can break it back up into powder with an old druggist's mortar I have in my junk.

Be sure you get sodium borate and not sodium carbonate.

RWL
09-25-2010, 12:24 AM
Once I learned that it was Petersons and not Peters, I found it on line.

Wares Direct had the best price and shipping combination.
Around $10 for Petersons No. 1 Blue, and $9.68 for Peterson's No.2 for cast iron. Both are 1 lb. cans.

RWL

Rich Carlstedt
09-25-2010, 02:09 AM
Just remember, black flux is dangerous to breath !
best to do it outside
Rich

lazlo
09-25-2010, 10:13 AM
Just remember, black flux is dangerous to breath !
best to do it outside

Oh wow, I didn't know that! What's in it?

38_Cal
09-25-2010, 02:27 PM
Lazlo, you can get in touch with the manufacturer and get a Material Safety Data Sheet for the flux. Some firms have them on line, others you'll have to ask for directly. The MSDS will list the hazardous ingredients, but the percentages for each one may read something like "1%-99%"...totaling well over (or under) 100% of the product. Wouldn't want to give away the actual recipe! :D

David

lazlo
09-25-2010, 04:03 PM
The MSDS's all read the same to me: prolonged exposure causes headaches, diarrhea, dizziness, shortness of breath, flatulence, impotence, stupidity...

It obviously contains boron and boric acid, but the primary ingredient is Potassium Tetraborate (another boron derivative) -- a close relative of Sodium Tetraborate: 20 Mule Team Borax. In other words, Black Flux is the Old Timer's Blacksmith recipe I posted above :)

Potassium Tetraborate 1332-77-0 30-40
Boric Acid 10043-35-3 20-30
Potassium Bifluoride 7789-29-9 20-30
Potassium Pentaborate 11128-29-3 1-5
Sodium Dodecyl Sulfate 151-21-3 0 – 0.5
Boron 7440-42-8 1-5
Water 7732-18-5 10-20