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Oxidizing or patinizing steel to matte gray

Does anyone have any ideas how I can Oxidize regular shiny steel to a gray matte finish, I have a vintage WW1 military item that originally was oxidized to a dull gray finish, But when I removed the rusty area's with a mild acid solution what I was left with,where the rust was, are shiny ares that need to be re-oxidized to a dull matte gray finish. There are very detailed area's that I need to keep sharp so I have to have something that is not too corrosive.
Thank You,

Ron Eckmyre
Antique restorer - Owosso, Michigan, USA
2006

Try 20 gm tannic acid ⇦ this on eBay or Amazon [affil links] /15 gm phosphoric acid/1 lit water solution(dark grey to black finish)-that is simple do it yourself rust converter ⇦ this on eBay or Amazon [affil links] . Colour can be corrected with black dyed clearcoat. Good luck!

Goran Budija
- Cerovski vrh Croatia
2006

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Thanks for that formula, Goran. But here in the U.S., and if not working with large amounts in a factory, buying a commercial product is more practical than buying the ingredients and mixing it yourself.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006