I have a few parts I am trying to sell, and I have to clean them up a little first. They are a old set of Alloy valve covers, and a 4bbl manafold. Well after sitting for two years in the trunk of my car, they have corroded a little bit. Got that white powder type stuff all over them. Any easy way to clean them up a bit? Not looking for perfict, just a little nicer looking to sell.