The last mention I saw of this on this site was a quick mention in 2006.
Has anyone heard of or used "Microseal" ? from their website: " Microseal consists of resins in a ketone solution and is used to seal porosity in all metals. It can be dipped, brushed or sprayed on to penetrate the pores. The solvent then evaporates leaving the pores sealed with resins." and "Our sealants are used by manufacturers of (and by people servicing) the following products: ... Boat and Marina Owners (salvaging metal water & diesel tanks)" Site says it is FDA approved for water tanks too.
Here's the web url: metal sealant, seal pump valves, Microseal
Sounds too good to be true ... Anyone have feedback on this product?