Ive heard great things about ZOOP seal, its a polish and a sealer that will last abuot a year. Might give it a try the kit is about $100 but Ive never heard anyone say it wasnt worth it. hth 2881
If you dont want to drop that kind of $$ just get a can of Mothers Mag and Aluminum polish. It works well also, just doesnt last as long or seal the surface to prevent more oxidation.