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Discussion Starter · #1 · (Edited)
Hey, I'm overhauling an old Schwinn Le Tour Luxe (1983 model), and building it back into a (relatively) nice road bike that still looks crappy. Most of the steel parts have surface rust, and aluminum parts are speckled with surface corrosion. However, I've everything works perfectly - I've disassembled, cleaned, and reassmebled all components. It's kind of fun to do this, actually - a bike that will be undesireable to steal, and looks like a beater. I'm putting in a relatively modern (but cheap) single-bolt alloy seatpost, and a sealed-cartridge BB. Only obviously unoriginal thing will be aero brake levers.

Anyway, the frame is in very good shape (full cro-moly, weighs 8.5 pounds for frame/fork/headset, 63.5cm frame size), has speckles of rust here and there, but I've treated it internally with Frame Saver so it won't rust out from the inside. The worst external rust is on the left side of the downtube, where the frame has been leaned against things to lock up the bike in the past. I'm wondering if this rust poses any structural danger to the frame. If it does, then refinish that part of the bike, or at least scrub it with a scotch-brite pad and put some rust-proof coating on there (the paint that you'd buy at an auto-body shop, that stops rust and looks crappy). If the rust is unlikely to pose any structural danger to the frame, then I'd prefer to leave it as-is, keeping with the bike's crappy-appearance motif.

The rust is not deep at all, just scarring on the surface of the tube where the paint had been worn away:

Any thoughts here? I appreciate any feedback. Thanks.
 

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Discussion Starter · #3 ·
collectorvelo said:
clean well and paint
will not be safer
but it will love better and slow down the final death of your frame
Thanks for your reply.
What I mean is, does the surface rust pictured pose any danger to speeding up the frame's death (as you describe it)? That's what I mean by safer.
It's my understanding that when steel frames to rust out, they almost always rust out from the inside. I've taken care of this by treating the inside of the tubes with Frame Saver.
What I'm trying to figure out is whether the external surface rust is going to propagate. If it ain't (assuming the bike isn't kept outside in the rain), then I'd just leave it as-is.
 

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Call me a neat freak or whatever but

rust on frames make me cringe. What about powdercoating the frame? All the rust will be removed and the finish will be real nice. Stock color like black will be cheap. I know, not what you are thinking, but you went this far, why not finish the job?
 

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Discussion Starter · #5 ·
Yeah, I've thought about powdercoating it - the frame is in good shape and was a good design to start with, and I've got a friend who recently redid the whole paint job on an old Le Tour Luxe - but my question in this thread is pretty specific. Does the small amount of surface rust pose any structural danger to the frame? If not, I'd like to leave it there, and have a true beater bike that looks ugly, and most people would think is junk, but actually rides like a very nice road machine. If the surface rust is structurally dangerous (which I doubt, but I want to confirm on this), then I'll sand that part, touch it up with some primer, and be done with it - and still have an ugly, perfectly working bike that wouldn't attract thieves.
 

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That oxidization doesnt look too terrible, unless it the oxidized material is 'flaking off then your talking structural damage'. Has it been stored outside for a long periods of time? The more water that gets to the frame really can ruin it. But if your saying its just where the paint has chipped its not so bad. I'd sandblast the frame and paint it.
 

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Discussion Starter · #7 ·
Angelracer said:
That oxidization doesnt look too terrible, unless it the oxidized material is 'flaking off then your talking structural damage'. Has it been stored outside for a long periods of time? The more water that gets to the frame really can ruin it. But if your saying its just where the paint has chipped its not so bad. I'd sandblast the frame and paint it.
Yeah, it's not flaking at all, so i don't think there's much danger of the rust propogating. There was a bit of rust on it when I got it, and my brother (who's been riding the bike this spring) left it outside a couple days in a row in the rain. But I cleaned it off right away, after telling him how stupid that was. I stripped the frame down and dried it out inside right away, and just now rustproofed it internally, one week later.

That said, the frame is nice enough to give it a good paint job. I may do that eventually. With the horz dropouts and no derailler hanger, it would also make a great fixed gear. Except the bottom bracket isn't very high.
 

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Rust on the frame should definitely be removed. Dry environment or no, the rust will eventually propagate completely through the tubing. Unlike other metal oxides, rust does not form a surface passivation layer. It's difficult to assess actual lifetimes, but even in the desert, iron and steel will eventually oxidize completely.

Another problem with leaving rust on the frame is that there isn't any easy way to assess structural integrity.

A bit of steel wool and sandpaper and one of the spray applicated 'rust removal' products (changes oxidation state to that of Fe3O4) should solve the problem and still keep the bike visually undesirable.
 

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Discussion Starter · #9 ·
achiral said:
Rust on the frame should definitely be removed. Dry environment or no, the rust will eventually propagate completely through the tubing. Unlike other metal oxides, rust does not form a surface passivation layer. It's difficult to assess actual lifetimes, but even in the desert, iron and steel will eventually oxidize completely.
Another problem with leaving rust on the frame is that there isn't any easy way to assess structural integrity.
A bit of steel wool and sandpaper and one of the spray applicated 'rust removal' products (changes oxidation state to that of Fe3O4) should solve the problem and still keep the bike visually undesirable.
Okay, that's the sort of information that I was looking for. Thanks for your help!
 

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Discussion Starter · #11 ·
Yeah, it's not been in the rain too much.

Here are email replies from a couple of friends from bikeforums, that I'd asked about this issue.
My opinion, as an engineer with a little bit of education in materials, metallurgy, and corrosion (hopefully not dangerous) is that you do not want to just let the rust go on its merry way. It will, and will not be your friend. Make it crappy looking some other way, like with bad, drippy paint, overspray, etc., but treat the rust as an enemy. The tubes are very thin, relative to the rust. The problem with iron oxide is that it is less dense than the uncorroded iron, it expands as it forms, and allows a corrosive environment (moisture and oxygen) to exist below, begetting more corrosion. Some oxides, such as aluminum and copper, are close enough in density that they form a protective barrier against further corrosion, but not our friend steel, oh no. There are a few specialty alloys of steel that do not obey this rule, but bike tubes are not in that family. If I remember correctly, you live in NC, a good incubator for corrosion.
In short time, the rust will go deeper. My guess is, Schwinn used tubes with enough meat so that this is not a failure issue. But, if not treated now, the pitting will cause a problem when you decide to refinish the downtube. In order to assure the rust is arrested, a pitted tube would have to be ground, which is a lot of work and would make the tube thinner. If I owned this bike, I would wet sand it with 180 then spray with a rust retarding, primary, flat paint. After allowing 48 hours for the paint to completely dry, I would take a hanful of mud and rub it over the painted area. That should stop the rust, but not compromise the 'beater bike' look you're trying to maintain.
 
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