This is basicly the same process as preping, cutting and buffing paint. It may be needed if u are considering nickle coating or chroming a part removing scratches or rust from aluminium/steal or just makin that bit of aluminium shine.
Be aware that most aluminium parts have a protective clear anodised coating, sanding cutting and buffing will remove this coating and leave it open to oxidisation requireing a sealant via wax or paint to keep it prtected
Can be applied to plastic (substituting approprate polish), alloys and metals to fix repairs and polish
You will need 400grit & 800grit wet and dry sandpaper, cutting compound (solid bar or liquid) and applicator which is normaly a felt or cloth wheel can also we a foam pad and the corresponding power tool.
Clean the part, scoure pad is the way to go using some strong thinners or De-oxidiser (dont use oven cleaner it will eat Aluminium if left on)
Remove anything you can bolts lugs ect
Sand & Prep
Start with the sanding using aprox 350-600 grit wet & dry sand paper keep going till its a good consistant finish
Move up to 800 Grit Sand paper or the course or medium course cutting compound which is normaly in block form. This should give you most of the shine.
Finish with a fine cutting compound using a seprate applicator
Using a paint made for use directly for metal, the metal will loose some of its shine but the surface will be maintanace free.
Anodisation can be used for aluminium but its difficult
Use a wax/silcon based polish to seal and protect the metal for oxidisation this will give a better looking finish but on aluminium it will be have to be constanyly mainted.