My 22 year old steel frame has developed a few small rust spots....most of them are approx 2 mm or so in size. So this spring I took a wire brush to one of them, then a dremel wire brush and got down to bare metal....and repainted....now a few months later the rust is BACK!!
So this brings up 2 questions:
1. What is the best way to get rid of these small rust spots?? My method obviously failed miserably. I used the search function and it looks like a solvent and clear nail polish may be involved.
2. More importantly....how "necessary" is it to get rid of these small rust spots? I dont really care about aesthetics, I am more concerned about longevity of the frame.
Most likely, your visible rust spots that you treated earlier were just that, the visible part of the rust. You probably need to stip back the paint in the immediate area until you get to "clean" metal.
Once you get there, normal prep and painting should take care of it. One thing you might try is good old naval jelly. You brush it on and rinse it off after a directed amount of time. Just be aware that once you apply the jelly and rinse it off, you MUST prep and prime immediately due to the bare metal being exposed to air and the immediate formation of oxidation.
I will try the naval jelly....do you think I can just apply touch-up paint and/or clear nail polish to the treated spots? I dont know much about primers, etc.
With your original spots only being 2mm, touch up paint might work. For priming, my suggestion is to drop by your local auto parts store, NAPA usually has a wide selection, and pick up some sandable primer.
Since your spots are relatively small, hopefully by the time you reach clean metal they will remain small. I have to qualify this that I am really anal about finishes, so I might be suggesting more than what you want to do.
1: Clean off you surrounding area until you have clean metal.
2: Treat with Naval Jelly to remove residual rust, and rinse.
3: Make sure there are no edges to your painted area to unpainted area transition, and mask off an area extrending a small way over you current paint.
4: Spray with a sandable primer. It's worth noting that there are several newer primers that specialize ini "encapsulating" rust, thus inhibiting it. They are hugely popular in the classic car world for frame work.
Let the primer dry to the touch and very lightly wet sand with 600 or 800 grit wet/dry sand paper until the primer feels smooth to the touch. I would allow the primer to dry over night/24 hrs to set up afterwards.
5: Spray a very light coats of paint to you masked area, allowing each coat to dry to a tacky degree. Hopefully you can find a matching paint in your color. Again, if the area is really small, you may get away with touch up paint. The biggest thing to consider here is that your paint on the frame be the same kind of paint you are applying. If you have a laquer based paint on your frame and apply an enamel, your eventually going to have the two paints react with each other, resulting in bubbling and flaking.
After you have aplied probably 2-3 light coats, allow the paint to set overnight. Afterwards, wet sand very lightly with 1000 and then 2000 grit sand paper until your finish is smooth. After your paint has set for several days and cured, you can then compound the area out to finish blending in your new paint with your older paint.
Again, I have to qualify that I'm extremely anal in my approach to finishes. I have found that with proper prep and appraoch, a rather decent finish can be had out of a quality shaker can. I recommend using Dupli Color or something along that line.
I'll readily admit that there are probably plenty of folks who would just clean it up and apply touch up paint. It might work if you can get the rust with the naval jelly. Just be sure to get the surrounding rust that's lurking under the surrounding paint.