The recent plasma cut gates have been given an initial sports of mild acid and set outside to start their patina. Once they are in place we’ll further chemically add different value colours (subtle shades of brown) to the different layers to further differentiate them from each other. In only a couple of days outside the rust colour evened out on the metal and it now looks vastly different than when we pulled them from the shop.
Published with permission from precisionboard.blogspot.com. Source.