Sounds like you have a lot of work ahead of you...
First off, the ridged area you are talking about is a machined finish, which is done on a lathe and usually clear coated afterwards...
Some aftermarket wheel manufacturers clear coat their polished and/or machined finish wheels when they are new, and others leave them bare metal. You are correct that aluminum doesn't rust, but it does oxidize. It also tends to get very dirty usually very quickly and loses its lustre. It can be gotten back, always, obviously, by polishing though, and a newly polished wheel is much shinier than a clear coated wheel. A clear coated wheel looks newer longer and cleans up the same way a painted wheel would, simple soap and water and it is usually back to new again, not requiring any heavy duty polishing...
-cody: maintenance forum moderator
2001 Lexus IS300 - 650whp/610wtq (Virtual Dyno)PTE 6765/AEM Infinity - Auburn Sky Pearl (1 of 1348)
2007 Lexus GS450h
2010 Lexus RX350
1998 Lexus GS300 - 1jz-GTE swap
1999 Isuzu VehiCross 285/75-16 Destination MT's - Astral Silver Metallic (1 of 1021) (for sale)