Rust back is a sad reality of life when it comes to working on vintage bikes.
I recently brought my cylinders to a friend’s shop to blast with glass media. The cylinders were a freaking mess walking in there. In particular, the cylinders had at least 2 or 3 layers of black paint, poorly applied, as well as visible rust.
The results of the media blasting was a beautiful, mostly clean surface. To be honest, I was kind of surprised how good they looked after getting all that old paint and rust off.
That is, they looked good temporarily – basically, they looked good until I came home and set them aside for a few weeks (while working on other projects around the house). I came back and there was a new layer of rust – a sad reality, but also something I kind of expected.
With old cylinders or fork legs or pretty much any old aluminum or iron once rust sets in, you can pretty much expect it to come back like persistent weeds on an otherwise beautiful lawn.
Rust Back – The Need to Know Info
Rust back is essentially rust that comes back in a short period of time after dry cleaning (sanding, abrasive blasting, etc.). The rust will generally reappear within a few hours to a week. The rust itself is usually the kind that is tightly adhered to the surface versus powdery (i.e. running your finger or a rag across it will not leave a residue on your hand). Finally, the location of the rust is sporadic – it will not be a uniform layer across everything, which is is common to new rust.
That pretty much defines rust back. Another way to look at it is that “flash rust” usually has a component of water involved, such as wet blasting, and new rust is usually powdery and more uniform.
Rust Back – What You Can Do About It
I hate to be the bearer of bad news, but there isn’t much that can be done about rust back accept really aggressive treatment. After removing the rust using an abrasive method such as sanding, blasting, grinding, the surface must be chemically treated – even though you no longer see the rust, there are almost certainly microscopic rust particulars forming the minute you stopped your dry cleaning. There are many rust neautralizing chemicals at your local hardware store. Just make sure you wear adequate skin and eye protection and follow the directions closely.
Once chemical treatment is complete, it is time for a thorough painting regiment. I recommend primer, paint, and clear coat. These will all protect your newly reconditioned surface. If you just rattle can over the old surface, you are more likely than not going to be dealing with the same problem next year when the paint starts to peel. Essentially rust will form under the rattle can painted surface.
Abrasive blasting is a few hours work. As opposed to cutting corners from there and having to do it all again, do it right the first time and have a beautiful surface for many years to come.
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