Originally Posted by
datlas
To muddy the waters further about powder coating, I just had some brief correspondence with a major custom framemaker about repainting, and when I told him I was planning on powder coating, he cautioned me that this does not protect against rust, and the slightest scratch will expose the metal and thus allow rust to form. He suggested it is better to go the old fashioned route of blast/primer/paint...
Any thoughts on the rust risks of powder coating would be appreciated. The frame is 22 years old and has minimal rust (a few spots of 1-2 mm).
He does have a point about steel frames: if the bare steel is exposed, it
will rust. Conventional wisdom says that powder coat is a
far more durable finish than paint, however. I believe powder coat generally ends up being thicker than paint and it's baked onto the frame at around 400-degrees. I don't have any scientific data to back that up; it's just what I've heard from
everyone in the business.
To satisfy my curiosity, I just took my pocket knife and tried to scratch two items: 1) the powder-coated fork recently discarded from my mountain bike, and 2) the painted finish from a 1974 Schwinn Typhoon cruiser that I'm planning to restore and refinish. It took me five scratches, with decent pressure, to get through the powder coat finish. The paint on the Schwinn gave up on the first scratch. Again, not a scientific test but it convinced me, at least, that powder coat is pretty durable.
P.S. the Krylon rattle-can paint job on my home-made welding cart didn't hold up any better than the Schwinn, nor did the factory paint on my 1990 Ford F250 truck. Your mileage may vary.