The extent of cleaning depends on how bad the oxidation/corrosion is. On some rims, I've simply just had to clean with neverdull swaps and polish with Mother's Aluminum/Metal polish. In more extreme cases, I've had to sand parts or all of the wheel face to get it back into shape. I can't stand clear coat on rims, and I strip it off if I get rims with it. It just cracks, peels, yellows, and traps junk under it. Sometimes the sanding just needs to be with 600 to 1500 grit sandpaper. Sometimes I've had to use 80 grit to get scratches, burrs, and marks around the wheel weights out. On my '85 pickup, the Eagle rims I bought just had a milled aluminum look. It wasn't shiney at all, and I sanded them down and polished them. By the time I was done it was almost as shiney as Chrome.