Corroded aluminium?

[phatphony]

when polishing aliminium a little trick i use is autosol aliminium polish then spray mrsheen over the top after polishing.the mr sheen gives it a waxy coating thus protecting it from the elements

[TPL]

Sand to 800 grit, then if you have a hand held grinder, install a buffing pad on it and apply buffing compound to it and you will be making very fast work of bringing those covers to a mirror finish, and you don't even have to remove the covers. Home depot sells the stick type compound marketed by Royobi, works great!

[GS ace]

You're so right JR. I steer my customers away from clear coat on aluminum engine parts.

[renobruce]

No need to clear coat IMHO. Get 'em shiny and use Mother's aluminum polish. It has a protectant in it...kind of like a wax. If you live in a humid place, go over them about once a month. None of my parts have been cleared and they still look as good as the day I did them with minimal upkeep.