Clean method for cast iron?

Hiya Jack and welcome. The problem with cast iron, especially a small piece is it will lose details due to the rust. I have found a few small things made from cast, and I have found that a small, soft bristle, stainless wire brush works quite well to remove the majority of the loose oxidation. Then I finish it up with a soft bristle brass brush. To preserve it with rust stop. This stuff will turn it black, but it won't continue to deteriorate.

I prefer to use Hydrochloric Acid or Muriatic acid as it is called in building supply stores or hardware stores. Use it as it comes from the bottle taking precautions such as gloves and vapor mask, or just use it out doors and avoid inhaling fumes. It only has to be dipped briefly, just keep checking it and when done rinse it in water and baking soda. The acid will quickly dissolve the iron oxide or rust and get down to solid metal. Sometimes the rust is the only record of details, and you might wish to preserve it, and other times it obscures the shape. In either case it is weak and unstable.

I use Naval Jelly. Just spray it on, wait a few minutes and rinse it off with water and a soft brush. Its available at most hardware stores. Be sure to use gloves!

Think any of those methods will work on these?

Found them at an old mill today. The buildings there were built from 1812-1911 and still stand.  I didn't find these detecting though. There is a river next to the mill and an old tree fell causing new erosion on the bank. I found these about 2 feet down in an area loaded with very old-looking bricks where i later found an old brick wall once stood. It was also 50 feet from a building built in 1814, which is still original on the exterior except for modern windows.


I think the long thing is a window counterweight. It's about 14" long and heavy. The other smaller straight piece looks like a pin and the circle looks like a loop of some sort.