Subject: [CR]Conserving Steel Frames
Cranky wrote:
"What I've
> seen is that rust begins at a tiny chip or break at the paint, but then
> spreads remarkably far under the paint. In a way I see this as a drawback
of using
> modern paints. On an old PX 10 the spot would be much more likely trust
and
> stop there. With the tougher modern paints, the film strength is
sufficient to
> both trap moisture and remain intact as rust travels beneath it."
You must be talking about filiform corrosion which usually manifests as a spider web trail of paint being pushed up off the tube. It doesn't really require a break in the paint to form. It is most usually caused by humidity and is most often found on the top tube where a rider has been dripping warm salty sweat.
On either a new frame or an old frame in for refinishing, the right surface preparation can virtually eliminate this type of corrosion. My technique is to use fine abrasive etching followed immediately by metal etching primer followed by epoxy primer followed by urethane top coats and clears. A lot of trouble, but it saves me and my customers time and agro in the long run.
To minimize corrosion on a frame already painted you can:
1. Wax the frame with a good automotive wax system.
2. Rinse the frame gently with cool water after a sweaty ride to get rid of the corrosive sweat residue.
3. Store the bike away from humidity.
Hugh Enox
La Honda