It is called "Filiform corrosion" from its resemblance to worm tracks. It often occurs to Aluminum which is coated by an impermeable coating that excludes Oxygen. It is quite commonly found under the paint on aircraft painted with polyurethane enamels. The only way to stop it for sure is to strip the finish and etch the surface with a liquid etchant as is used when refinishing aircraft. It can then be glass beaded and re-finished with "Ceracoat" or one of the other baked on finishes.
S&W may refinish or replace the gun under warrantee, even though they state clearly cosmetics are not covered by the "Lifetime Warrantee". Call them, not E-mail, and ask. 800-331-0852. Worst they can do is say no!
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Gunsmithing since 1961
Last edited by Alk8944; 09-20-2016 at 11:44 PM.
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