It's been quite a while since I've used this technique to clean rough looking aluminum rims (anything with black oxidation pock-marks), but I was going to put the winter wheels on my wife's car and noticed that they looked really bad, so I decided to give them back some of their original shine. What you need to do this is:
- Spray can of oven cleaner,
- stiff brush with a long handle,
- masking tape (not really essential)
- a cool day (today it was close to freezing here)
- garden hose with sprayer or bucket with sponge & water.
Here's the explanation with pictures. The first one here shows one of the rims before cleaning (it actually looks better in this picture than it did in real life):
The next 2 pictures show the tires with the masking tape on and they're already sprayed with oven cleaner. I let the cleaner sit on the rim for about 5 minutes and then I use the brush to get the cleaner into all the oxide (I give the whole outside a good scrub), then I spray another coat on and let this sit for another while (the cooler it is, the longer you can let it sit - today, I left it for about 10 minutes). Now when you give the rim the second scrubbing, you'll see most of the black oxide disappear & if you want, you can give it another spray and go through this process one more time (no more than 5 minutes on the very last stage).
Finally, I washed off all the dirty cleaner and removed the tape and here's an example of what I got:
Keep in mind that oven cleaner is caustic and can "eat" into aluminum, but you aren't heating up your rims like you would your oven and you aren't leaving it on long, so the chemical reaction is there for long enough to get the oxide off & give you some of the old shine back. The pock marks will still be there, but they won't be grey or black, they'll be a nice unpolished aluminum color and up close, you'll see them, but a couple of steps back, it looks good. If you wanted to retain this look, you'd need to coat the rim with a clear coat that would stick to aluminum (you can buy spray cans of that - it's made for respraying rims).
If the outside temperature is HOT, do 1 rim at a time and wash the cleaner off after you see most of the oxide removed - just keep scrubbing and watch it disappear. The oven cleaner works faster when the rim is warm.