Pitted aluminum rims are caused by salt that gets under the clear coat and eats away at the aluminum. Use 220-grit sandpaper when cleaning pitted aluminum rims with help from car restoration specialists in this free video on car maintenance.
In this video I'm going to show you how to clean a pitted aluminum rim. There's a good chance that if your rim looks like this, it's caused from salt getting under the clear coat and pitting the aluminum. The only way to get it off is to sand it down. Once the pitting is in the aluminum, it actually eats the aluminum, so you have to take it off with an abrasive. For this I'm using sandpaper, two hundred and twenty grit. I like two-twenty grit because it doesn't take off too much surface of the aluminum and doesn't scar it up so bad but it still takes off the oxidation and pitting. Once you've cleaned the rim and you have the bare aluminum it's time to protect it. There's two ways you can go about it. One you could spray a clear coat on. Just like that Rust-O-Leum you see in the picture. It's just a clear coat of paint that will protect the rim. The other way is you could use a paste wax like you would for the paint on the vehicle of your car. Both will work but you will have to reapply the paste wax from time to time.