BlastRadius

Hello,
I've been working on repainting the frame of a '80/'81 Trek 412 that had chipped
paint and rust showing at those exposed areas. After some paint stripping I noticed
that there's surface rust on most of the frame, even where the paint was intact and
nowhere near the chipped paint. Could this be from rust creeping under the paint
while the bike was in damp storage or did Trek just paint over surface rust at the
factory?

Astra

I can't see any rust in those photo's...

BlastRadius

That reddish-brown stuff isn't rust?

sch

Looks like a candidate for walnut hull or other 'soft' cutting material via a blaster
to me. Then have it powder coated to armor plate it. Steve

dobber

Never seen rust peel before.

BlastRadius

That little dangling thing is a strip of paint I scraped back with a razor. The rust seems to be underneath the paint.

Astra

It looks too even to be rust, maybe some kind of undercoat or metal treatment. If it IS rust, it looks like it only really on the bits that look to have been exposed for a long time.

If it IS rust, it looks so mild that a bit of wire wool would remove it with minimal effort; it doesn't look pitted at all.

BlastRadius

Thanks, I'm planning on Naval Jellying it after I strip the paint. Then primer and repaint. The rust on the inside of the top tube looks to be the worst so I hope some clean-up and Rust Reformer will do the trick.

ofofhy

A lot of the alloy steels readily form a surface oxide (rust for lack of better terms) that actually protects it from further corrosion. That may be the even brown coating that you are seeing. Steel tubing is rarely "silver" in color without some sort of cleaning procedure. What I would consider true "rust", is the loose powdery/flaky stuff that has a gritty texture. The surface oxide will have a smoother feel to it.

BlastRadius

That makes sense. So a frame manufacturer, for a low end frame, wouldn't necessarily take the time to clean the frame of surface oxidation before it painted it, correct?

mtbikerinpa

That is the case for non-ferrous (not steel) tubing. Steel tubing however is prone to rusting underneath paint or sometimes through paint if it isnt waxed. Paint is ever so slightly porous, thus allowing some moisture in. In the better frame paint jobs they apply a phosphate coating that works in a similar manner to galvanize and gives it a matte brownish/darkish color. If it looks even, then it is the phosphate, otherwise you are in fact seeing early rust formation.