Painting Chromoly Steel

Question

I was trying to paint my bare chromoly steel bicycle frame and fork. I sanded the frame and fork with 120 grit sandpaper to give it a slightly rough surface for the paint to adhere to. I used a quick-drying acrylic rattle can spray paint to apply primer to it.

I waited for more than 24 hours to apply the top coat (same brand and paint type). I stuck masking tape to check if the primer would come off, it didn't. I applied a little too much of the top coat so there were runs on some parts of the frame. I tried wiping the runs with a rag thinking that only the top coat would be wiped off. Unfortunately, when I wiped it off, the primer went with the top coat.

Is that supposed to happen when I wipe off a fresh top coat? I'm not sure if the metal was still too smooth for painting but it is scuffed. Also, for runs, if I can't wipe it off, do I just wait for it to dry and sand to smooth out the surface and then reapply another layer of top coat?

By the way, these are the instructions on the can:

It doesn't say how long the paint dries

Answer 1

As mikes indicated, the chemicals in your top coat reactivated your primer coat, much like if you were to write something in sharpie, it is dry to the touch, but if you were to wipe alcohol over it it would smear.

I use aerosol cans for a lot of different types of painting, and unfortunately drips are often impossible to remove without a lot of sanding or starting over. The best method is to avoid them in the first place with good technique. I realize this sounds a bit arrogant but correcting them often leads to more issue and the clear coat not laying smooth.

You can wait for them to dry, sand the entire area or tube smooth and start over. Don't only sand the area of the drip or you will get an uneven surface.

As they say in the autobody world, paint is 90% prep and 10% skill. When using rattle cans it also helps to let the cans sit in warm/hot water for several minutes before use. This allows the internal temp to rise and allows the paint to atomize more efficiently. You may also find "artists" paints used for graffiti murals don't drip as easily and they are very heavily pigmented and a bit thicker paint. Brands as an example would be, Belton Molotow, Montana, Loop, and Flame amongst others.

Also when sanding large areas or tubes, you should not hand sand as your fingers push at different pressures making the sanding stroke uneven, this can be remedied by using an electric sander, block or something similar, ive also found for round tubes a thick cloth or towel behind the strip of sand paper works well for pulling around a circular shape, the cloth helps prevent the sandpaper from tearing and gives nice even pressure.

Good Luck!