Aug 23, 2011· Hey guys, I need to paint a customer project. The material is 3003, mill finish, aluminum sheet metal. The desired finish is Navy Blue. I have researched the net, local body shop, and my local Sherwin Williams store. Every where I look I get different answers. Etching primer, etch wash, non-etch wash, MEK, etc.... Can anyone here offer advice and facts based upon experience?