Deflux/Derust before Reflux?

[ToddFarr]

This might be a silly question, but this is my first jigged frame so here it goes.

I'm getting ready to tack the frame, after I tack and check alignment do I need to deflux and derust everything applying new flux before I finish all the brazing. Or Do I just throw more flux on the cool hardened flux and continue on?
Also, I am planning on doing the front and rear triangles separate, so when you deflux everything in a water bath the BB area gets awfully rusty. On my last frame I spend hours removing all the rust inside and outside before I refluxed and brazed on the chain stays. Looking through some Sach's photos today in FNL, it seems the outside of the bottom bracket is pretty rusty although the chainstays are getting ready to be brazed.

Thanks in advance as always -Todd.

[e-RICHIE]

Assemble, tack, check, and braze atmo. Add more flux after the tack is cooled and checked, but before brazing. But don't linger between operations. There's a small window of time you can waste and not be concerned about the original flux going awry. But since you are new, don't waste it.

[e-RICHIE]

On my last frame I spend hours removing all the rust inside and outside before I refluxed and brazed on the chain stays. Looking through some Sach's photos today in FNL, it seems the outside of the bottom bracket is pretty rusty although the chainstays are getting ready to be brazed.

Heh? There's no rust on my parts. I brazed that joint 30 minutes after I shot the pics. And the stays/shell had the requisite 3.9992228 pounds of flux on them atmo.

[ToddFarr]

I was referring to this picture here, and more so talking about after the front triangle is all finished and the rear triangle is prepared to be brazed.

IMG_3266 | Flickr - Photo Sharing!

I am assuming the inside is cleaned and cleared from rust, but does that rust on the outside surface affect the flux in a negative way?

I hope this clarifies my comment

-Todd.

[e-RICHIE]

There's no rust there atmo. After the main triangle is soaked and worked on, some of the areas that are untouched are discolored from the drying process. But that's not rust. And regardless, the brazing goes inside the c/stay ports so in theory the exterior is not part of the equation. But if there was rust, or oil, or gazpacho, I would not be going forward until it was clean room clean. PS the gazpacho reference was levity.

[ToddFarr]

So you are saying that orange on the BB shell is not iron oxide? What is it?

[e-RICHIE]

So you are saying that orange on the BB shell is not iron oxide? What is it?

I dunno what it is, but I am saying I don't care, and it's not affecting the work atmo!

[ToddFarr]

Thanks for the reply, sorry for all the questions. I'm just the type of person who likes to understand the what and the why of the processes I am learning about. It definitely clears it up for me. I spent way to much time on my last frame cleaning up similar discoloration when I could have just worried about the insides of the joints. I guess I was worried about that affecting the flux, but I guess flux is designed to keep the metals from oxidizing during the heating process, so if that is in fact oxidization it wouldn't get any worse during brazing I suppose.

Thanks for you help!

[e-RICHIE]

Thanks for the reply, sorry for all the questions. I'm just the type of person who likes to understand the what and the why of the processes I am learning about. It definitely clears it up for me. I spent way to much time on my last frame cleaning up similar discoloration when I could have just worried about the insides of the joints. I guess I was worried about that affecting the flux, but I guess flux is designed to keep the metals from oxidizing during the heating process, so if that is in fact oxidization it wouldn't get any worse during brazing I suppose.

Thanks for you help!

Put away the questions, the science, and the books. Grab some pics, or videos, or watch others - and then channel these. Once you learn how to do it (anything), you'll understand it better atmo. No snark or condescension intended.

[e-RICHIE]

Put away the questions, the science, and the books. Grab some pics, or videos, or watch others - and then channel these. Once you learn how to do it (anything), you'll understand it better atmo. No snark or condescension intended.

Thinking about this ^ it probably doesn't translate well in 1s and 0s.
Keep the questions coming atmo.
Balance them with hand's-on labor and endless repetition until something becomes second nature.

[busdriver1959]

Todd, I've had good luck derusting with a product called Kleen Strip Prep & Etch. It's made for prepping concrete for staining. My mentor for my first frames recommended it. I brush it on with an old toothbrush, wait about 5 minutes and wipe it off with a paper towel. It takes the rust off with almost no effort in a very short amount of time. However, if you don't wipe it off soon enough, it will dry to a film but that doesn't seem to have a negative effect if I scrub it off with a scouring pad.
This stuff isn't easy to find though. Home Depot carries it but out of the 6 HD locations near me, only one has it. I checked Amazon and it shows up there if you can't find it locally.

[Mark Kelly]

Or go to any car place and buy 3M rust dissolver. They're all based on phosphoric acid.

I buy conc. phosphoric from my local brewing supply and dilute it to suit.

[Dallas Tex]

Todd, I've had good luck derusting with a product called Kleen Strip Prep & Etch. It's made for prepping concrete for staining. My mentor for my first frames recommended it. I brush it on with an old toothbrush, wait about 5 minutes and wipe it off with a paper towel. It takes the rust off with almost no effort in a very short amount of time. However, if you don't wipe it off soon enough, it will dry to a film but that doesn't seem to have a negative effect if I scrub it off with a scouring pad.
This stuff isn't easy to find though. Home Depot carries it but out of the 6 HD locations near me, only one has it. I checked Amazon and it shows up there if you can't find it locally.

I'd be much, much more concerned about contaminating the joint with some cleaning fluid and/or paper towel residue than anything I saw in that pic referenced by the op. imho.

[steve garro]

Don't waste time polishing shit that doesn't need polishing.
That's what a sandblaster is for before paint.
If it's going to get brazed, make it clean-clean, if not, proceed.
Skip the perfect shoe-shine camera op & get on with getting the unit to paint.
There's enough work without doing things that do not need doing.
- Garro.

[steve garro]

IMG_4480.JPG

Or go to any car place and buy 3M rust dissolver. They're all based on phosphoric acid.

I buy conc. phosphoric from my local brewing supply and dilute it to suit.

Everything in this shop is cleaned with three things: hot soapy water with Dawn dish soap, 80 grit and 91% rubbing alcohol.
Gratuitous brazing shot, De Nada.
- Garro.

[Eric Estlund]

I'm an 80g man. I "mechanically clean" the surface immediately before brazing, and get on with it.

PS- I have recently started juicing my soak tank with a dash of metal prep. Helps cut down on the surface oxides if I have to soak between operations.

[c-cycles]

This story always comes to my mind when I read of cleaning joints with chemicals before brazing...

[Andrew R Stewart]

I mechanical clean as soon before I braze. 80 grit usually, although little braze one I'll usually just wire wheel off.

I was at NAHBS when Steve gave his talk and told us of his near death experience. Very eye opening. We get so focused on the surface we're torching that we can forget what's behind it. Andy. (Who has melted rubber jaws, scortched wood blocks and lit his sweater's sleeve on fire before).

[Mark Kelly]

In brewing we use phosphoric to clean tanks that are still under CO2 pressure (you should see what happens when you use caustic).

Brewers are fanatical about cleanliness and about residue levels, if rinsed properly phosphoric leaves nothing behind to be concerned about.

I'm using citric acid wash, water rinse then following with an acetone degrease immediately before brazing (on bike parts, not brewing tanks). I understand Paterek recommends using hydrochloric acid - I understand that's a really bad idea especially on stainless due to chloride stress corrosion cracking and hydrogen embrittlement.

[dbohemian]

This story always comes to my mind when I read of cleaning joints with chemicals before brazing...

That story although sad is a train wreck from the very beginning....When I was first read that years ago it I was like.....oh, no you didn't....oh wait, OH no YOU didn't! and then I was like, Holy Crap, you did....

Safety is 1 part understanding and 9 parts common sense.

de-grease, 80 grit and then a thorough wipe with denatured alcohol. Clean you rods too. That is all