The nature of rust
 

Is rust an active thing? What I mean is, once rust developes does it take on a chemical life of it's own and keep eating your metal forever? Or if you, for example, put a coat of wax over some surface rust, does that stop it in its tracks?

I've got a Schwinn Le Tour III that's got spots of surface rust and a 98 Rockhopper with some internal rust (bb mostly). The Schwinn I went over the frame completely with wd-40 and scotchbrite, so it's looking as nice as it can without touch-up paint, and all I've done is wax it real good. On the rust spots I didn't sand them down to bare metal or anything, just cleaned them up as well as I could. Are they going to be static? Assuming I keep them coated in wax, the rust isn't still eating away under there, right?

And the rockhopper, there was enough rust to have some actual flaking in the bb shell. I've cleaned it out real good too- without going down to new, bare metal. If I frame-saver it will that stop the rust from growing (assuming it stays dry and clean)?

A friend and I were discussing this yesterday. We passed a construction site (large building). Lots of steel beams were rusted, and they just sprayed foam over the beams. We decided that rust (coversion of Fe to FeOx needs transfer of oxygen. As long as the foam was gas impermiable, and the foam structure was sound, the rust process would not continue. However, if you paint over rust, the paint will not adhear. It will flake off and the rust will continue. I would not trust wax to be gas impermiable, and I would not expect it to stay on the bike over rust spots.

from what I've seen...

RUST NEVER SLEEPS!!!:rolleyes:

That's right, it never sleeps and as long as it has moisture, and the dissolved oxygen that is in the water, then the process continues. If paint or wax or whatever was "perfect", that is it completely sealed off the rust, then the rust would be starved of "fuel" and the oxidizing would be arrested. Problem is, none of these coatings are perfect, they all have microscopic pores or they wear away or develop tiny cracks...and then the moisture/oxygen finds it's way in to feed the monster...shudder! Best bet is to remove it as COMPLETELY as possible, apply a chemical neutralizer (like phosphoric acid) and coat as thoroughly as you can, I guess a powder coat would probably be a better barrier than most common paints...then maintain the paint by waxing as often as needed to keep it protected from water intrusion. Or you just have to embrace the process and learn to love the slow death that is rust...

Hmmmm. Well I'm in so-cal, so I've got a geographic leg-up on the battle, I suppose.

yeah, but...depends: Mojave Desert or Malibu? If you're close to salty air, even nice warm sunshine-y salt air, you're going to get horrid rust as well as aluminum corrosion. But, a nice tan anyway.

I think most cosmetic rust isnt that revelant as long as you take good care "killing it"-LOL. But some of the Rust even on cars in Boston area is thick and just plain bad.

The problem for steel is that iron oxide is a flaky, porous material that can contain substantial amounts of oxygen, so that when it is sealed over with paint or whatever there is still a ton of O2 under the seal that can continue to rust the metal. Also iron oxide has a tendancy to flake off and take the sealant material with it, reexposing the rusting area.

That's why you need to remove all rust before repainting, to keep from trapping oxygen under the seal and to provide a firm base on which the paint can bond.

The good thing about rust on steel (unlike aluminum pitting) is the frame can be rusted very badly without becoming much weaker. You can see a bike covered in rust and once you have it cleaned off the bike is still in very good shape mechanically and structurally. Aluminum tends to pit right at the most important parts, and pits grow into the metal, while steel "general" rusting is a cosmetic, surface problem that takes a very long time to progress.

Right now I'm just gonna go with the wax. I'm too busy, poor and lazy to try to find a place to mix me some touch up paint. It's pearlescent so I think it'd be tricky. And I really want to get this thing running. The pictures below show the sort of rust bits it has. Nothing major, I think if I keep an eye on them I'll be OK. This thing hung in a garage for 20 years and that's as bad as it got, and I'm inland LA so, fingers crossed, I guess. All the chrome components were totally rusted though. They left big caked-on rings of rust. You can see the headset a little in one of the photos and it's totally shot, chrome-wise but for now this level of restoration is good for me.

Good info though, very helpful. Thanks. Rust. Damn it to hell, huh?

http://img224.imageshack.us/img224/9...inn16yr.th.jpghttp://img145.imageshack.us/img145/3...inn27yb.th.jpg
http://img124.imageshack.us/img124/5...inn36tz.th.jpghttp://img145.imageshack.us/img145/4...inn47pb.th.jpg

Better to burn out than it is to rust


I had my Jeep wrangler repainted. They ground most of the rust off, but must have missed some. Several months after the repaint the same old rust spots began to bubble back up from under the paint. For the life of me I can't figure out what caused the bubbles from under the inside of the paint, except that they didn't get all the rust and it continued to work. It's possible the chemical make up of the paint also allowed the rust spots to come back after they failed to remove it all? I'm not sure but there seem to be plenty of examples of places where Oxygen can't get (the metal under the new paint) but that rusts from the inside out. Maybe in the paint though there was enough oxygen left from the old rust pockets.



If you want to temp fix it put "Rust Converter" on it. The Rust Convert chemically changes rust into black primer.

In my mispent youth, I did some work in a body shop and did some body work on a classic 64 Buick.
OK, some of the examples provided in the previous posts are surface rust, others are embedded rust that is permeating the metal, possibly from both sides (eg. probably the Jeep). Wax will temporarily stop or slow down the oxidation process, provided you removed the loose rust and the spot is only surface rust. There are inexpensive auto products that are designed to be painted or 'penned' on and will stop the rust, dead, permanently. I think they sell this stuff in a 'pen' applicator. I used such a product on a 2 year old Buick that someone tried to break into. Seven years later, the rust never returned. Rustoleum, iron oxide red can acheive the same result.
If the frame is rusting from the inside, as auto fenders usually do, you have to invest bucks now or face a broken frame in the near future. That's why cars are repaired by cutting out the rusted metal and replacing it with new sheet metal.
From your pictures, it looks like you have surface rust. The spot on the chain stay looks like the loose rust was not removed. It that is correct, the rust will return quickly. I would try to smooth out those spots with a small piece of fine emory cloth, but don't sand the painted surface since you don't want to repaint, then put some sort of paint or rust inhibitor over it.

Rust is at times used as a protective coating.Until blueing gunsmiths use browning(controled rusting) to protect the finish.But what applies to your bicycle is all of the above not browning.