Please ignore my size-challenged valve stem :-)
Got some great results, following Chris Fix's video, for the most part.
If you want to do this, make sure you are working in above 15C, it's not overly humid (if it's raining, there's fog or it's otherwise damp, do it another time) and you have plenty of light.
Some rims are better for this than others. Chris' rims had a nice and even surface whereas mine have a ditch all around the edges where the valve goes. This made it pretty nasty to try to remove all the rust in there so I sanded as much as could be bothered, then painted over. Six months later there is no sign of rust yet, so it may be fine for good.
Follow the instructions on your spray cans over the ones below, please.
Update approximately 8 months later
Because, as I said below, I did not properly sand the rims, the rust broke through the paint again. However, that only happened in the places where there was left over rust. The places where I properly sanded down everything, where there was rust before, are now perfectly fine.
For example: the circular holes on the perimeter on the rim were perfectly cleared of any rust, so they did not rust at all. Those were very rusty under the dirt you see in the comparison.
As opposed to the holes which are perfect, the inner well of the rim is now rusty again on my back wheels, because on those I could not properly remove the rust with the tools I had at the time.
Because on those rims I now have nothing to lose, I hit them repeatedly with a small hammer to see if the paint is holding up. To my surprise, I couldn't damage the paint beyond creating chips, so the paint is perfectly bonded to the rim where the rust was completely removed, whereas on the areas where there was rust, it's falling off at the lightest hammer hit.
The process
- Clean rim.
- Sand using preferred method until no rust is visible (where possible).
- Here you can use either normal sandpaper by hand, or you can machine sand using a sanding brush. For the above, I machine sanded the wheel.
- If you used a low grit in previous step, step up to at least 800 and sand again.
- Brush to remove sanding debris.
- Don't skip this. If your rims are similar to mine, metal wire from the sanding brush can get in small crevices.
- Blow compressed air on the rim too if you can.
- Mask off tire.
- Put a garbage bag over the tire and cut 1-2cm away from the rim in a circle.
- Use a flat side of the bag to not cause an annoyance. I cut mine along the seams and used one of the resulting pieces.
- Remove the garbage bag for now.
- Put any painter's tape around the rim as close as possible but without covering the edges of the rim at all.
- Tape the garbage bag over the painter's tape with more tape.
- Put a garbage bag over the tire and cut 1-2cm away from the rim in a circle.
- Degrease using alcohol and something lint-free.
- Apply at least 4 light coats of spray primer waiting around 10 minutes in between.
- Wait 30 minutes.
- Apply at least 4 light coats of spray paint waiting around 10 minutes in between.
- I used base+clear spray here.
- Remove the mask. This can be reused. If it shrank and became annoying, cut it and re-tape it together in the best shape.
- Let the rim cure for at least a few hours. Read the spray can instructions.
- Consider repainting your center caps as well while you wait for the rim to cure. To remove my center caps, I had to just hammer them out using a screwdriver. If you hit from all sides you won't do any damage to it and you can reuse them.
What to do if rim came out matte
This can happen if you did the last layers wrong or it was humid or too cold outside.
I had this happen for one of my rims and the fix was to simply polish it. It took quite a bit of hand polishing but in the end you can't spot the difference at all. Let the paint cure for a few days before doing this, and clean the rim first obviously.
I used Meguiars Ultimate Polish (not compound) to fix mine. You could try with compound as well but be careful not to overdo it, as spray paint is not as tough as automotive paint.
After some spray paint and covers for the lug nuts, painted center caps and some cheapo tire shine that was free at the local car wash, the difference is huge, even though the job I did was far from perfect. I'm very happy with the results.