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Too much rust to repair or remove?

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Too much rust to repair or remove?

Old 06-18-13, 10:50 PM
  #1  
wernst
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Too much rust to repair or remove?

I have an opportunity to buy a Tange tubed frame from the 80's, and it has some rust; the worst is on the bottom of the down tube entering the bottom bracket.



Is this too much rust to salvage for the home mechanic? For a professional frame builder? I assume the frame will need repainting, so let's just talk rust removal, I guess.

Thanks,
Warr
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Old 06-18-13, 11:19 PM
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Warr- What would be telling is if the frame was stripped of paint and the rusty areas lightly sand blasted would there still be pitting. You can emulate this with local application of sand paper. Andy.
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Old 06-20-13, 03:49 AM
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If you do a search for oxalic acid or OA bath, you will get hits on a bunch of threads on the C and V side of the house. Wade through them and you will find before and after shots of some pretty surprising transformations. I don't think you have more rust than many of them plus, the paint isn't affected by OA.
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Old 06-20-13, 05:37 AM
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Once you strip the paint off and try sand blasting it, you can purchase a product called "metal prep." It is very good at getting into pits to dissolve rust. Also, if you do not want to spend the money on that, you can use muratic acid which you should be able to find cheaply at any pool supply store. Mix the MA 50/50 with water, spray on rust areas, and let it do its work. The MA does the same as the metal prep. Make sure whatever you do, to do it in a WELL ventilated area. Once rust/pits are gone, use some sort of lacquer thinner or acetone to prep the bare metal and prime it with an etch prime. Viola.
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Old 06-20-13, 08:44 AM
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I would never in a million years mess with muriatic acid for any bike related task, just about anything is a better alternative; the very small amout of $ you save is not worth the risk. Everything about it is EXTREMELY TOXIC. I've use the stuff in our pool to balance ph for years and have tons of respect for its potency/danger.

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Old 06-20-13, 02:35 PM
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Originally Posted by calstar View Post
I would never in a million years mess with muriatic acid for any bike related task, just about anything is a better alternative; the very small amout of $ you save is not worth the risk. Everything about it is EXTREMELY TOXIC. I've use the stuff in our pool to balance ph for years and have tons of respect for its potency/danger.

Brian
Just providing options. I deal in car restoration and use it from time to time on real rusty things. Yes toxic, use gloves and a respirator, go outside and aim fans on you. Just use common sense.
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Old 06-21-13, 09:45 AM
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Originally Posted by calstar View Post
I would never in a million years mess with muriatic acid for any bike related task, just about anything is a better alternative; the very small amout of $ you save is not worth the risk. Everything about it is EXTREMELY TOXIC. I've use the stuff in our pool to balance ph for years and have tons of respect for its potency/danger.

Brian
Some folks live in fear of anything construed as "extremely toxic." Muriatic acid can be dangerous if handled improperly but, if it were all bad they wouldn't sell gallon jugs at Home Depot for you to add to your swimming pool water. Just handle properly.

Muriatic Acid has many uses. I've used it for years for a couple purposes. One is to remove aluminum deposits on chrome cylinder walls in two cycle engines that have seized. Another is to remove thinset from the backs of tiles when when a restoration is done and "vintage" tiles are not available cheaply. Bicycle useage? It will eat a stuck seatpost.

You'll be fine- open it downwind and let the jug breathe for a bit. Wear safety glasses and rubber gloves.
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Old 06-21-13, 10:10 AM
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Originally Posted by calstar View Post
I would never in a million years mess with muriatic acid for any bike related task, just about anything is a better alternative....
Still my belief, go for it for whatever reason you may have. I'm an old guy with many years of working with and around toxic mtls and agents, my point of view is much more conservative now than it used to be, especially given options.

be safe,

Brian
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Old 06-21-13, 10:33 AM
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Why not use Oxylic Acid? Available at local hardware stores as wood bleach. Mix with water and soak over night.
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Old 06-22-13, 12:12 PM
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oxalic is a much more appropriate treatment. There are many threads in the vintage forum about using it. If muriatic acid was a good treatment, it would be in much wider use. For a frame, get a cheap kiddie pool and soak the frame in an oxalic acid bath.
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Old 06-24-13, 10:06 AM
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Here's the bike in question on ebuy. 64cm



and the link

http://www.ebay.com/itm/Schwinn-Prol...item4174407cb0

sold for $76+$30 shipping, 28 bids
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Old 06-24-13, 10:27 AM
  #12  
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I nearly gave up on a Peugeot UO-8 - It had been sitting under a deck in Galveston for years and was covered with pitting rust - My son and I took a fiber-optic bore scope to it and checked the inside before doing anything more to it - BRAVO - Inside it was clean and upon removing the bottom bracket we realized it had been Linseed oil treated - After rebuilding he still uses it as his major ride - Anyway - More to the point - Strip and inspect....

You can always take the frame over to your local gunsmith for a look...
(I have found most gunsmiths to be bicycle fans even if they don't ride)

Just as it stands this bike is a beauty...
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Old 06-25-13, 08:29 AM
  #13  
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Corrosion along the lug edge can occur if the flux was not properly removed after brazing. Flux is corrosive and will eat at the joint if not removed completely after brazing. Framebuilders typically have a dunk tank of some sort to soak the frame after brazing so all the flux is removed, including that which is inside the tubes. Media blasting or scrapping flux off the outside of the tubes is only half the job.

I'd be somewhat reluctant to purchase a frame such as listed due to the possibility of internal corrosion. Most likely that's not the case, but it's hard to say for sure by looking at a photo.
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Old 06-25-13, 09:02 AM
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my experience is that flux isn't that corrosive. I had a fork that had flux on it for almost 30 years and the metal under the flux was shiny whereas the rest of the fork was covered in rust. I can't imagine a frame was painted with any flux remaining, that just doesn't happen. Rust happens around lug edges because the paint fails there first.
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Old 06-25-13, 09:37 AM
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I thought that the flux re tarded oxidation not accelerated it? I'm very new to this stuff so I'm really ignorantly asking.

Edit. I know how to spell re tarded but the censor blocks it out. Sadly, I'm using it correctly.
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Old 06-25-13, 04:40 PM
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https://en.wikipedia.org/wiki/Brazing

Flux
In the case of brazing operations not contained within an inert or reducing atmosphere environment (i.e. a furnace), flux is required to prevent oxides from forming while the metal is heated. The flux also serves the purpose of cleaning any contamination left on the brazing surfaces. Flux can be applied in any number of forms including flux paste, liquid, powder or pre-made brazing pastes that combine flux with filler metal powder. Flux can also be applied using brazing rods with a coating of flux, or a flux core. In either case, the flux flows into the joint when applied to the heated joint and is displaced by the molten filler metal entering the joint. Excess flux should be removed when the cycle is completed because flux left in the joint can lead to corrosion, impede joint inspection, and prevent further surface finishing operations.



One of my first frames had issues because I didn't clean the flux out from inside the tubes. After a year or so of use, noticed some paint bubbling around the bottom bracket shell edges. Flux was propagating out of porosity in the braze joint. I blame myself of course, and learned the hard way the importance of cleaning flux out from inside tubes. When building forks and brazing stays, I like to have a hole on each end so water can get inside the tubes and get rid of the flux. Your mileage may vary.
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Old 06-25-13, 05:58 PM
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Thanks. That was a helpful read.
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Old 06-26-13, 09:49 AM
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Originally Posted by wernst View Post
I have an opportunity to buy a Tange tubed frame from the 80's.....
Werntz, did you get the frame?
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Old 06-28-13, 12:01 PM
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Originally Posted by calstar View Post
Werntz, did you get the frame?
Nah. I ultimately decided to work on another project. But it was tempting though...

-W
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Old 09-11-13, 02:33 PM
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Was just reading Sheldon Browns guides to frame refinishing. Worth a read.
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